Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Sudeep Holla]

On 04/07/17 08:31, Peter De Schrijver wrote:
> On Mon, Jul 03, 2017 at 10:17:22AM +0100, Sudeep Holla wrote:
>>
>>
>> On 01/07/17 19:14, Uwe Kleine-König wrote:
>>> Hello,
>>>
>>> On Sat, Jul 01, 2017 at 07:02:48AM +0200, Dirk Behme wrote:
>>
>> [...]
>>


 The other problem is security related. If, at all, you have to do it the
 other way around, then:

 Make Linux a consumer of the other CPU's (trusted/trustzone/whatever
 secured) OS clock driver.
>>
>> Yes, that's better and is getting common on newer platforms. They have
>> separate M-class(or even low A-class e.g. A5/A7) processors to handle
>> all the system management.
>>
>> The new ARM SCMI specification[0][1] is designed to standardize the
>> interface. It covers the clocks in clock protocol.
>>
> 
> Yes, however this doesn't exist on older SoCs which still have multiple CPU's
> 

Agreed. But if someone is fixing/adding support in Linux as well as in
the other OS running on those cores, why not consider this interface
instead of trying to generalize something which will invariably SoC
specific.
-- 
Regards,
Sudeep

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Peter De Schrijver]

On Mon, Jul 03, 2017 at 10:17:22AM +0100, Sudeep Holla wrote:
> 
> 
> On 01/07/17 19:14, Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Sat, Jul 01, 2017 at 07:02:48AM +0200, Dirk Behme wrote:
> 
> [...]
> 
> >>
> >>
> >> The other problem is security related. If, at all, you have to do it the
> >> other way around, then:
> >>
> >> Make Linux a consumer of the other CPU's (trusted/trustzone/whatever
> >> secured) OS clock driver.
> 
> Yes, that's better and is getting common on newer platforms. They have
> separate M-class(or even low A-class e.g. A5/A7) processors to handle
> all the system management.
> 
> The new ARM SCMI specification[0][1] is designed to standardize the
> interface. It covers the clocks in clock protocol.
> 

Yes, however this doesn't exist on older SoCs which still have multiple CPU's

Peter.

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Sudeep Holla]

On 01/07/17 19:14, Uwe Kleine-König wrote:
> Hello,
> 
> On Sat, Jul 01, 2017 at 07:02:48AM +0200, Dirk Behme wrote:

[...]

>>
>>
>> The other problem is security related. If, at all, you have to do it the
>> other way around, then:
>>
>> Make Linux a consumer of the other CPU's (trusted/trustzone/whatever
>> secured) OS clock driver.

Yes, that's better and is getting common on newer platforms. They have
separate M-class(or even low A-class e.g. A5/A7) processors to handle
all the system management.

The new ARM SCMI specification[0][1] is designed to standardize the
interface. It covers the clocks in clock protocol.

> 
> That doesn't matter much. Either way the first CPU has to provide the
> master side of this device (as it needs clks for booting up) and the 2nd
> gets this virtual clk device that forwards clk requests to the first
> CPU.
> 
> On my machine (Udoo Neo, A9 + M4) the A9 is the primary CPU that is
> started by the bootrom. If I want the M4 being the primary device I'd
> need support in the bootloader to wait long enough (i.e. until the M4 is
> up) before letting the A9 jump into Linux.

I think that is platform specific. On few platforms I have seen
recently, it's M4 or whatever core that handles system power management
boots first and is responsible to even boot secondaries.

> Managable I'd say. This way would even make sense if the M4 runs a
> rt critical OS that shouldn't be forced to wait on the non-rt A9 to> enable a 
> clk.
> 

Exactly.

-- 
Regards,
Sudeep


[0] http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/index.html
[1] https://marc.info/?l=devicetree=149849482623492=2

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Geert Uytterhoeven]

Hi Uwe,

On Sun, Jul 2, 2017 at 11:23 AM, Uwe Kleine-König
 wrote:
> On Sun, Jul 02, 2017 at 07:48:41AM +0200, Dirk Behme wrote:
>> > On my machine (Udoo Neo, A9 + M4) the A9 is the primary CPU that is
>> > started by the bootrom. If I want the M4 being the primary device I'd
>> > need support in the bootloader to wait long enough (i.e. until the M4 is
>> > up) before letting the A9 jump into Linux. Managable I'd say. This way
>> > would even make sense if the M4 runs a rt critical OS that shouldn't be
>> > forced to wait on the non-rt A9 to enable a clk.
>>
>> Overall, assuming that the issue we are discussing here can be solved quite
>> easily in hardware (a set of clock registers for each CPU/OS domain,
>> connected cleverly to effectively control each clock, with access protection
>> for each set of registers) I tend to think that for a SoC supposed to run
>> different OS on different cores this is a missing hardware feature (bug?).
>
> So you want to enable bits for your CAN clock, one in each cpu's domain.
>
> I'd say that is a nice idea that a hardware engineer might be proud to
> pick up but that results in more headache than fun for the software
> colleague.
>
> There are several problems that come immediately to mind:
>
>  - You can switch of a clk because you don't need it on, or because you
>need it off. I guess you want to have the clock on if at least one
>cpu wants it on. So you take away the freedom from the other cpu to
>force the clock off. (Yeah, the currently available clk framework
>doesn't allow that either.)
>  - What if cpu 0 sets the parent of the can clk to pll2 but cpu 1 wants
>it set to pll1? How does cpu 1 notice the change?
>  - On off might be relatively easy, what about clk dividers? cpu 0 sets
>2 which cpu 1 sets 6.
>
> That convinces me that the disadvantages of having two views on the clk
> core have more weight and you really want a single view and share that
> by software.

Renesas ARM SoCs already implement (parts of) that.

There are separate sets of the Module SToP register bits for each set of
CPUs. Only if all sets agree the clock supply to a module will be stopped,
which can be monitored using the status Registers.
So for the CAN modules itself there is no issue, as the clock supply to the
modules will not be stopped as long as the RT CPU keeps it enabled.
There must be more to it (secure mode?), as some R-Car Gen3 module clocks
cannot seem to be disabled by disabling them for all documented CPU sets.

There's also a global bit to prevent modifying any clock register.
This could be used to prevent changing the CAN parent clock (changing
its divider and/or stopping it). However, as this is a global bit, it would
affect the full Linux clock driver.

Again, probably there's more to it when using secure mode...

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Uwe Kleine-König]

Hello Dirk,

On Sun, Jul 02, 2017 at 07:48:41AM +0200, Dirk Behme wrote:
> > On my machine (Udoo Neo, A9 + M4) the A9 is the primary CPU that is
> > started by the bootrom. If I want the M4 being the primary device I'd
> > need support in the bootloader to wait long enough (i.e. until the M4 is
> > up) before letting the A9 jump into Linux. Managable I'd say. This way
> > would even make sense if the M4 runs a rt critical OS that shouldn't be
> > forced to wait on the non-rt A9 to enable a clk.
> 
> 
> Overall, assuming that the issue we are discussing here can be solved quite
> easily in hardware (a set of clock registers for each CPU/OS domain,
> connected cleverly to effectively control each clock, with access protection
> for each set of registers) I tend to think that for a SoC supposed to run
> different OS on different cores this is a missing hardware feature (bug?).

So you want to enable bits for your CAN clock, one in each cpu's domain.

I'd say that is a nice idea that a hardware engineer might be proud to
pick up but that results in more headache than fun for the software
colleague.

There are several problems that come immediately to mind:

 - You can switch of a clk because you don't need it on, or because you
   need it off. I guess you want to have the clock on if at least one
   cpu wants it on. So you take away the freedom from the other cpu to
   force the clock off. (Yeah, the currently available clk framework
   doesn't allow that either.)
 - What if cpu 0 sets the parent of the can clk to pll2 but cpu 1 wants
   it set to pll1? How does cpu 1 notice the change?
 - On off might be relatively easy, what about clk dividers? cpu 0 sets
   2 which cpu 1 sets 6.

That convinces me that the disadvantages of having two views on the clk
core have more weight and you really want a single view and share that
by software.

Best regards
Uwe

-- 
Pengutronix e.K.   | Uwe Kleine-König|
Industrial Linux Solutions | http://www.pengutronix.de/  |

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Dirk Behme]

On 01.07.2017 20:14, Uwe Kleine-König wrote:

Hello,

On Sat, Jul 01, 2017 at 07:02:48AM +0200, Dirk Behme wrote:

On 30.06.2017 22:24, Uwe Kleine-König wrote:

Hello,

On Fri, Jun 30, 2017 at 10:58:26AM -0500, Rob Herring wrote:

TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
disables them as being unused.


not long ago I thought with a few colleagues about this. The scenario is
to start a Linux kernel on a Cortex-M companion to a Cortex-A.


On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:

With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
CLK_IS_CRITICAL") we are able to handle critical module clocks.
Introduce the same logic for critical core clocks.

Signed-off-by: Dirk Behme 
---
Commit

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f

is quite nice to avoid *module* clocks being disabled. Unfortunately,
there are *core* clocks, too. E.g. using an other OS on the Cortex R7
core of the r8a7795, the 'canfd' is a quite popular core clock which
shouldn't be disabled by Linux.

Therefore, this patch is a proposal to use the same 'mark clocks as
critical' logic implemented for the module clocks for the core
clocks, too.

Opinions?


On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
core which may run another OS.
This is an interesting issue, and relevant to other SoCs, too.

In this particular case, the "canfd" clock is a core clock used as an
auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
to three scenarios:
1. Linux controls all CAN interfaces
   => no issue,
2. The OS on the RT CPU controls all CAN interfaces
   => issue, Linux disables the clock
3. Mix of 1 and 2
   => More issues.
Of course this is not limited to clocks, but also to e.g. PM domains.

How can this be handled?
I believe just marking the "canfd" clock critical is not the right solution,
as about any clock could be used by the RT CPU.

Still, Linux needs to be made aware that devices (clocks and PM domains) are
controlled by another CPU/OS.

Should this be described in DT? It feels like software policy to me.


No, it shouldn't. It is Linux policy to disable all unused clocks, so
Linux gets to deal with the consequences.


The ideal solution I imagine is to make the other CPU's OS a consumer of
the Linux clock driver. This would require a generic device driver on the
companion CPU that forwards clk requests via inter-cpu communication to
the Linux clk driver. It could be feed with the necessary information by
the rproc glue. So when the companion cpu is supposed to care for the
can0 device, the steps that should happen are:

   - make sure can0 isn't occupied by the Linux Host
   - reroute the can irq to the companion cpu (if necessary)
   - create a dtb containing something like this for the companion CPU:

clks: virtclk {
compatible = ???
#clock-cells = <1>;
...
};

can@$address {
compatible = ...
regs = ...
clocks = < 3>;
clock-names = ...
...
};

 where the driver binding to the virtclk device just forwards clk
 requests to the Linux host side which then knows that clk 3 is the
 can clock and does the necessary stuff.

This way the can clock doesn't need special handling in the host's dtb
and no clock necessary for the companion is disabled as unused because
it is requested and enabled.

The only problem I see is that implementing such a driver/protocol
probably is time consuming.



The other problem is security related. If, at all, you have to do it the
other way around, then:

Make Linux a consumer of the other CPU's (trusted/trustzone/whatever
secured) OS clock driver.


That doesn't matter much. Either way the first CPU has to provide the
master side of this device (as it needs clks for booting up) and the 2nd
gets this virtual clk device that forwards clk requests to the first
CPU.

On my machine (Udoo Neo, A9 + M4) the A9 is the primary CPU that is
started by the bootrom. If I want the M4 being the primary device I'd
need support in the bootloader to wait long enough (i.e. until the M4 is
up) before letting the A9 jump into Linux. Managable I'd say. This way
would even make sense if the M4 runs a rt critical OS that shouldn't be
forced to wait on the non-rt A9 to enable a clk.



Overall, assuming that the issue we are discussing here can be solved 
quite easily in hardware (a set of clock registers for each CPU/OS 
domain, connected cleverly to effectively control each clock, with 
access protection for each set of registers) I tend to think that for 
a SoC supposed to run different OS on different cores this is a 
missing hardware feature (bug?).


Best regards

Dirk

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Uwe Kleine-König]

Hello,

On Sat, Jul 01, 2017 at 07:02:48AM +0200, Dirk Behme wrote:
> On 30.06.2017 22:24, Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Fri, Jun 30, 2017 at 10:58:26AM -0500, Rob Herring wrote:
> > > > TL;DR: Clocks may be in use by another CPU not running Linux, while 
> > > > Linux
> > > > disables them as being unused.
> > 
> > not long ago I thought with a few colleagues about this. The scenario is
> > to start a Linux kernel on a Cortex-M companion to a Cortex-A.
> > 
> > > > On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  
> > > > wrote:
> > > > > With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
> > > > > CLK_IS_CRITICAL") we are able to handle critical module clocks.
> > > > > Introduce the same logic for critical core clocks.
> > > > > 
> > > > > Signed-off-by: Dirk Behme 
> > > > > ---
> > > > > Commit
> > > > > 
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
> > > > > 
> > > > > is quite nice to avoid *module* clocks being disabled. Unfortunately,
> > > > > there are *core* clocks, too. E.g. using an other OS on the Cortex R7
> > > > > core of the r8a7795, the 'canfd' is a quite popular core clock which
> > > > > shouldn't be disabled by Linux.
> > > > > 
> > > > > Therefore, this patch is a proposal to use the same 'mark clocks as
> > > > > critical' logic implemented for the module clocks for the core
> > > > > clocks, too.
> > > > > 
> > > > > Opinions?
> > > > 
> > > > On r8a7795, there are several Cortex A cores running Linux, and a 
> > > > Cortex R7
> > > > core which may run another OS.
> > > > This is an interesting issue, and relevant to other SoCs, too.
> > > > 
> > > > In this particular case, the "canfd" clock is a core clock used as an
> > > > auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
> > > > to three scenarios:
> > > >1. Linux controls all CAN interfaces
> > > >   => no issue,
> > > >2. The OS on the RT CPU controls all CAN interfaces
> > > >   => issue, Linux disables the clock
> > > >3. Mix of 1 and 2
> > > >   => More issues.
> > > > Of course this is not limited to clocks, but also to e.g. PM domains.
> > > > 
> > > > How can this be handled?
> > > > I believe just marking the "canfd" clock critical is not the right 
> > > > solution,
> > > > as about any clock could be used by the RT CPU.
> > > > 
> > > > Still, Linux needs to be made aware that devices (clocks and PM 
> > > > domains) are
> > > > controlled by another CPU/OS.
> > > > 
> > > > Should this be described in DT? It feels like software policy to me.
> > > 
> > > No, it shouldn't. It is Linux policy to disable all unused clocks, so
> > > Linux gets to deal with the consequences.
> > 
> > The ideal solution I imagine is to make the other CPU's OS a consumer of
> > the Linux clock driver. This would require a generic device driver on the
> > companion CPU that forwards clk requests via inter-cpu communication to
> > the Linux clk driver. It could be feed with the necessary information by
> > the rproc glue. So when the companion cpu is supposed to care for the
> > can0 device, the steps that should happen are:
> > 
> >   - make sure can0 isn't occupied by the Linux Host
> >   - reroute the can irq to the companion cpu (if necessary)
> >   - create a dtb containing something like this for the companion CPU:
> > 
> > clks: virtclk {
> > compatible = ???
> > #clock-cells = <1>;
> > ...
> > };
> > 
> > can@$address {
> > compatible = ...
> > regs = ...
> > clocks = < 3>;
> > clock-names = ...
> > ...
> > };
> > 
> > where the driver binding to the virtclk device just forwards clk
> > requests to the Linux host side which then knows that clk 3 is the
> > can clock and does the necessary stuff.
> > 
> > This way the can clock doesn't need special handling in the host's dtb
> > and no clock necessary for the companion is disabled as unused because
> > it is requested and enabled.
> > 
> > The only problem I see is that implementing such a driver/protocol
> > probably is time consuming.
> 
> 
> The other problem is security related. If, at all, you have to do it the
> other way around, then:
> 
> Make Linux a consumer of the other CPU's (trusted/trustzone/whatever
> secured) OS clock driver.

That doesn't matter much. Either way the first CPU has to provide the
master side of this device (as it needs clks for booting up) and the 2nd
gets this virtual clk device that forwards clk requests to the first
CPU.

On my machine (Udoo Neo, A9 + M4) the A9 is the primary CPU that is
started by the bootrom. If I want the M4 being the primary device I'd
need support in the bootloader to wait long enough (i.e. until the M4 is
up) before letting the A9 jump into Linux. Managable I'd say. This way
would 

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Dirk Behme]

On 30.06.2017 22:24, Uwe Kleine-König wrote:

Hello,

On Fri, Jun 30, 2017 at 10:58:26AM -0500, Rob Herring wrote:

TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
disables them as being unused.


not long ago I thought with a few colleagues about this. The scenario is
to start a Linux kernel on a Cortex-M companion to a Cortex-A.


On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:

With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
CLK_IS_CRITICAL") we are able to handle critical module clocks.
Introduce the same logic for critical core clocks.

Signed-off-by: Dirk Behme 
---
Commit

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f

is quite nice to avoid *module* clocks being disabled. Unfortunately,
there are *core* clocks, too. E.g. using an other OS on the Cortex R7
core of the r8a7795, the 'canfd' is a quite popular core clock which
shouldn't be disabled by Linux.

Therefore, this patch is a proposal to use the same 'mark clocks as
critical' logic implemented for the module clocks for the core
clocks, too.

Opinions?


On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
core which may run another OS.
This is an interesting issue, and relevant to other SoCs, too.

In this particular case, the "canfd" clock is a core clock used as an
auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
to three scenarios:
   1. Linux controls all CAN interfaces
  => no issue,
   2. The OS on the RT CPU controls all CAN interfaces
  => issue, Linux disables the clock
   3. Mix of 1 and 2
  => More issues.
Of course this is not limited to clocks, but also to e.g. PM domains.

How can this be handled?
I believe just marking the "canfd" clock critical is not the right solution,
as about any clock could be used by the RT CPU.

Still, Linux needs to be made aware that devices (clocks and PM domains) are
controlled by another CPU/OS.

Should this be described in DT? It feels like software policy to me.


No, it shouldn't. It is Linux policy to disable all unused clocks, so
Linux gets to deal with the consequences.


The ideal solution I imagine is to make the other CPU's OS a consumer of
the Linux clock driver. This would require a generic device driver on the
companion CPU that forwards clk requests via inter-cpu communication to
the Linux clk driver. It could be feed with the necessary information by
the rproc glue. So when the companion cpu is supposed to care for the
can0 device, the steps that should happen are:

  - make sure can0 isn't occupied by the Linux Host
  - reroute the can irq to the companion cpu (if necessary)
  - create a dtb containing something like this for the companion CPU:

clks: virtclk {
compatible = ???
#clock-cells = <1>;
...
};

can@$address {
compatible = ...
regs = ...
clocks = < 3>;
clock-names = ...
...
};

where the driver binding to the virtclk device just forwards clk
requests to the Linux host side which then knows that clk 3 is the
can clock and does the necessary stuff.

This way the can clock doesn't need special handling in the host's dtb
and no clock necessary for the companion is disabled as unused because
it is requested and enabled.

The only problem I see is that implementing such a driver/protocol
probably is time consuming.



The other problem is security related. If, at all, you have to do it 
the other way around, then:


Make Linux a consumer of the other CPU's (trusted/trustzone/whatever 
secured) OS clock driver.


Best regards

Dirk

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Uwe Kleine-König]

Hello,

On Fri, Jun 30, 2017 at 10:58:26AM -0500, Rob Herring wrote:
> > TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
> > disables them as being unused.

not long ago I thought with a few colleagues about this. The scenario is
to start a Linux kernel on a Cortex-M companion to a Cortex-A.

> > On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:
> >> With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
> >> CLK_IS_CRITICAL") we are able to handle critical module clocks.
> >> Introduce the same logic for critical core clocks.
> >>
> >> Signed-off-by: Dirk Behme 
> >> ---
> >> Commit
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
> >>
> >> is quite nice to avoid *module* clocks being disabled. Unfortunately,
> >> there are *core* clocks, too. E.g. using an other OS on the Cortex R7
> >> core of the r8a7795, the 'canfd' is a quite popular core clock which
> >> shouldn't be disabled by Linux.
> >>
> >> Therefore, this patch is a proposal to use the same 'mark clocks as
> >> critical' logic implemented for the module clocks for the core
> >> clocks, too.
> >>
> >> Opinions?
> >
> > On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
> > core which may run another OS.
> > This is an interesting issue, and relevant to other SoCs, too.
> >
> > In this particular case, the "canfd" clock is a core clock used as an
> > auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
> > to three scenarios:
> >   1. Linux controls all CAN interfaces
> >  => no issue,
> >   2. The OS on the RT CPU controls all CAN interfaces
> >  => issue, Linux disables the clock
> >   3. Mix of 1 and 2
> >  => More issues.
> > Of course this is not limited to clocks, but also to e.g. PM domains.
> >
> > How can this be handled?
> > I believe just marking the "canfd" clock critical is not the right solution,
> > as about any clock could be used by the RT CPU.
> >
> > Still, Linux needs to be made aware that devices (clocks and PM domains) are
> > controlled by another CPU/OS.
> >
> > Should this be described in DT? It feels like software policy to me.
> 
> No, it shouldn't. It is Linux policy to disable all unused clocks, so
> Linux gets to deal with the consequences.

The ideal solution I imagine is to make the other CPU's OS a consumer of
the Linux clock driver. This would require a generic device driver on the
companion CPU that forwards clk requests via inter-cpu communication to
the Linux clk driver. It could be feed with the necessary information by
the rproc glue. So when the companion cpu is supposed to care for the
can0 device, the steps that should happen are:

 - make sure can0 isn't occupied by the Linux Host
 - reroute the can irq to the companion cpu (if necessary)
 - create a dtb containing something like this for the companion CPU:

clks: virtclk {
compatible = ???
#clock-cells = <1>;
...
};

can@$address {
compatible = ...
regs = ...
clocks = < 3>;
clock-names = ...
...
};

   where the driver binding to the virtclk device just forwards clk
   requests to the Linux host side which then knows that clk 3 is the
   can clock and does the necessary stuff.

This way the can clock doesn't need special handling in the host's dtb
and no clock necessary for the companion is disabled as unused because
it is requested and enabled.

The only problem I see is that implementing such a driver/protocol
probably is time consuming.

Best regards
Uwe

-- 
Pengutronix e.K.   | Uwe Kleine-König|
Industrial Linux Solutions | http://www.pengutronix.de/  |

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Rob Herring]

On Thu, Jun 29, 2017 at 4:27 AM, Geert Uytterhoeven
 wrote:
> Hi Dirk,
>
> CC clock, ARM, DT, PM people
>
> TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
> disables them as being unused.
>
> On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:
>> With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
>> CLK_IS_CRITICAL") we are able to handle critical module clocks.
>> Introduce the same logic for critical core clocks.
>>
>> Signed-off-by: Dirk Behme 
>> ---
>> Commit
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
>>
>> is quite nice to avoid *module* clocks being disabled. Unfortunately,
>> there are *core* clocks, too. E.g. using an other OS on the Cortex R7
>> core of the r8a7795, the 'canfd' is a quite popular core clock which
>> shouldn't be disabled by Linux.
>>
>> Therefore, this patch is a proposal to use the same 'mark clocks as
>> critical' logic implemented for the module clocks for the core
>> clocks, too.
>>
>> Opinions?
>
> On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
> core which may run another OS.
> This is an interesting issue, and relevant to other SoCs, too.
>
> In this particular case, the "canfd" clock is a core clock used as an
> auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
> to three scenarios:
>   1. Linux controls all CAN interfaces
>  => no issue,
>   2. The OS on the RT CPU controls all CAN interfaces
>  => issue, Linux disables the clock
>   3. Mix of 1 and 2
>  => More issues.
> Of course this is not limited to clocks, but also to e.g. PM domains.
>
> How can this be handled?
> I believe just marking the "canfd" clock critical is not the right solution,
> as about any clock could be used by the RT CPU.
>
> Still, Linux needs to be made aware that devices (clocks and PM domains) are
> controlled by another CPU/OS.
>
> Should this be described in DT? It feels like software policy to me.

No, it shouldn't. It is Linux policy to disable all unused clocks, so
Linux gets to deal with the consequences.

Rob

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Peter De Schrijver]

On Thu, Jun 29, 2017 at 11:27:28AM +0200, Geert Uytterhoeven wrote:
> Hi Dirk,
> 
> CC clock, ARM, DT, PM people
> 
> TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
> disables them as being unused.
> 

There is that but also Linux should not be allowed to change the rate and
parent. Otherwise your R7 sw will likely fail as well. I think it makes sense
to have some DT property which informs linux which clocks it should not touch.
At least assuming clock control isn't moved to a separate coprocessor. In that
case any policy can ofcourse be implemented in the coprocessor.

Peter.


> On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:
> > With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
> > CLK_IS_CRITICAL") we are able to handle critical module clocks.
> > Introduce the same logic for critical core clocks.
> >
> > Signed-off-by: Dirk Behme 
> > ---
> > Commit
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
> >
> > is quite nice to avoid *module* clocks being disabled. Unfortunately,
> > there are *core* clocks, too. E.g. using an other OS on the Cortex R7
> > core of the r8a7795, the 'canfd' is a quite popular core clock which
> > shouldn't be disabled by Linux.
> >
> > Therefore, this patch is a proposal to use the same 'mark clocks as
> > critical' logic implemented for the module clocks for the core
> > clocks, too.
> >
> > Opinions?
> 
> On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
> core which may run another OS.
> This is an interesting issue, and relevant to other SoCs, too.
> 
> In this particular case, the "canfd" clock is a core clock used as an
> auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
> to three scenarios:
>   1. Linux controls all CAN interfaces
>  => no issue,
>   2. The OS on the RT CPU controls all CAN interfaces
>  => issue, Linux disables the clock
>   3. Mix of 1 and 2
>  => More issues.
> Of course this is not limited to clocks, but also to e.g. PM domains.
> 
> How can this be handled?
> I believe just marking the "canfd" clock critical is not the right solution,
> as about any clock could be used by the RT CPU.
> 
> Still, Linux needs to be made aware that devices (clocks and PM domains) are
> controlled by another CPU/OS.
> 
> Should this be described in DT? It feels like software policy to me.
> 
> Note that we (mainline) currently don't describe the Cortex R7 core in DT.
> Dirk: do you describe it?
> 
> Summary:
>   1. Core/module clocks are described in the clock driver (not in DT),
>   2. Unused clocks are disabled by CCF,
>   3. Clocks may be in use by the Real-Time CPU core, running another OS,
>   4. How to communicate to Linux which clocks are under control of the RT CPU?
> 
> Thanks for your comments!
> 
> >  drivers/clk/renesas/clk-div6.c | 17 +++--
> >  drivers/clk/renesas/clk-div6.h |  4 +++-
> >  drivers/clk/renesas/r8a7795-cpg-mssr.c |  7 +++
> >  drivers/clk/renesas/renesas-cpg-mssr.c |  3 ++-
> >  drivers/clk/renesas/renesas-cpg-mssr.h |  8 
> >  5 files changed, 35 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/clk/renesas/clk-div6.c b/drivers/clk/renesas/clk-div6.c
> > index 0627860..5917e05 100644
> > --- a/drivers/clk/renesas/clk-div6.c
> > +++ b/drivers/clk/renesas/clk-div6.c
> > @@ -18,6 +18,7 @@
> >  #include 
> >  #include 
> >
> > +#include "renesas-cpg-mssr.h"
> >  #include "clk-div6.h"
> >
> >  #define CPG_DIV6_CKSTP BIT(8)
> > @@ -184,7 +185,9 @@ static const struct clk_ops cpg_div6_clock_ops = {
> >  struct clk * __init cpg_div6_register(const char *name,
> >   unsigned int num_parents,
> >   const char **parent_names,
> > - void __iomem *reg)
> > + void __iomem *reg,
> > + const struct cpg_mssr_info *info,
> > + unsigned int id)
> >  {
> > unsigned int valid_parents;
> > struct clk_init_data init;
> > @@ -246,6 +249,15 @@ struct clk * __init cpg_div6_register(const char *name,
> > init.name = name;
> > init.ops = _div6_clock_ops;
> > init.flags = CLK_IS_BASIC;
> > +   if (info) {
> > +   for (i = 0; i < info->num_crit_core_clks; i++)
> > +   if (id == info->crit_core_clks[i]) {
> > +   pr_devel("DIV6 %s setting 
> > CLK_IS_CRITICAL\n",
> > +name);
> > +   init.flags |= CLK_IS_CRITICAL;
> > +   break;
> > +   }
> > +   }
> > init.parent_names = parent_names;
> > init.num_parents = 

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Geert Uytterhoeven]

Hi Dirk,

On Thu, Jun 29, 2017 at 11:27 AM, Geert Uytterhoeven
 wrote:
> CC clock, ARM, DT, PM people
>
> TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
> disables them as being unused.

> Of course this is not limited to clocks, but also to e.g. PM domains.

BTW, how do you prevent Linux from powering down the CR7 PM domain,
which contains the Cortex R7?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Geert Uytterhoeven]

Hi Dirk,

On Thu, Jun 29, 2017 at 12:28 PM, Dirk Behme  wrote:
> On 29.06.2017 11:27, Geert Uytterhoeven wrote:
>> CC clock, ARM, DT, PM people
>>
>> TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
>> disables them as being unused.
>>
>> On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme 
>> wrote:
>>> With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
>>> CLK_IS_CRITICAL") we are able to handle critical module clocks.
>>> Introduce the same logic for critical core clocks.
>>>
>>> Signed-off-by: Dirk Behme 
>>> ---
>>> Commit
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
>>>
>>> is quite nice to avoid *module* clocks being disabled. Unfortunately,
>>> there are *core* clocks, too. E.g. using an other OS on the Cortex R7
>>> core of the r8a7795, the 'canfd' is a quite popular core clock which
>>> shouldn't be disabled by Linux.
>>>
>>> Therefore, this patch is a proposal to use the same 'mark clocks as
>>> critical' logic implemented for the module clocks for the core
>>> clocks, too.
>>>
>>> Opinions?
>>
>> On r8a7795, there are several Cortex A cores running Linux, and a Cortex
>> R7
>> core which may run another OS.
>> This is an interesting issue, and relevant to other SoCs, too.
>>
>> In this particular case, the "canfd" clock is a core clock used as an
>> auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
>> to three scenarios:
>>1. Linux controls all CAN interfaces
>>   => no issue,
>>2. The OS on the RT CPU controls all CAN interfaces
>>   => issue, Linux disables the clock
>>3. Mix of 1 and 2
>>   => More issues.
>> Of course this is not limited to clocks, but also to e.g. PM domains.
>>
>> How can this be handled?
>> I believe just marking the "canfd" clock critical is not the right
>> solution,
>> as about any clock could be used by the RT CPU.
>>
>> Still, Linux needs to be made aware that devices (clocks and PM domains)
>> are
>> controlled by another CPU/OS.
>>
>> Should this be described in DT? It feels like software policy to me.
>>
>> Note that we (mainline) currently don't describe the Cortex R7 core in DT.
>> Dirk: do you describe it?
>
> No, we don't describe anything R7 related in DT, too.
>
>> Summary:
>>1. Core/module clocks are described in the clock driver (not in DT),
>>2. Unused clocks are disabled by CCF,
>>3. Clocks may be in use by the Real-Time CPU core, running another OS,
>>4. How to communicate to Linux which clocks are under control of the RT
>> CPU?
>
>> Thanks for your comments!
>
> While I appreciated that the overall issue is discussed, I'm not sure if
> there is anything really special we don't support generally, yet.
>
> We have an infrastructure to mark clocks enabled anywhere else to be not
> disabled by Linux kernel (CLK_IS_CRITICAL). From my point of view, for this
> infrastructure, it doesn't matter, where this 'anywhere else' is. To take
> some concrete Renesas RCar3 examples, from my point of view it doesn't
> matter if its a GIC-400 clock enabled in the boot loader (U-Boot) or a CAN
> clock enabled by the R7. In both cases marking them as critical on Linux
> side does the trick.

Yes, it does the trick. But is it the proper solution?

> The issue I just want to address (discuss) with this RFC patch is that for
> Renesas RCar3 we have CLK_IS_CRITICAL support for module clocks, but not for
> core clocks. From my point of view, this is a completely Renesas
> implementation specific discussion.

Correct. How the Renesas CPG/MSSR driver decides which clocks are marked
critical is a Renesas-specific implementation issue.
And indeed, currently the driver only handles critical module clocks
(more specifically, the GIC module clock, due to the lack of runtime PM
support in the GIC driver).
It does not handle critical core clocks, as so far no use case required
such support.

> So I would rephrase the initial sentence above
>
> "Clocks may be in use by another CPU not running Linux, while Linux disables
> them as being unused."
>
> to anything like
>
> "Clocks may be enabled (used) by others (U-Boot/CPUs/Hypervisors), while
> Linux disables them as being unused"

If a clock is used by Linux, Linux must make sure it is enabled when
needed.
If a clock is needed to run Linux, without driver support, Linux must still
make sure it is enabled. This is were critical clocks enter the game.
The above includes CPU clocks.

If a clock is used by U-Boot, U-Boot must make sure it is enabled when
needed.  Once U-Boot has transferred control to Linux, this no longer
matters.

if a clock is used by a HV, the HV must make sure it is enabled when
needed. I believe this is handled in secure mode? R-Car Gen3 SoCs already
have several module clocks that cannot be disabled (i.e. MSTPSRx != OR of
all yMSTPCRx).

If a clock is 

Re: Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Dirk Behme]

On 29.06.2017 11:27, Geert Uytterhoeven wrote:

Hi Dirk,

CC clock, ARM, DT, PM people

TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
disables them as being unused.

On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:

With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
CLK_IS_CRITICAL") we are able to handle critical module clocks.
Introduce the same logic for critical core clocks.

Signed-off-by: Dirk Behme 
---
Commit

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f

is quite nice to avoid *module* clocks being disabled. Unfortunately,
there are *core* clocks, too. E.g. using an other OS on the Cortex R7
core of the r8a7795, the 'canfd' is a quite popular core clock which
shouldn't be disabled by Linux.

Therefore, this patch is a proposal to use the same 'mark clocks as
critical' logic implemented for the module clocks for the core
clocks, too.

Opinions?


On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
core which may run another OS.
This is an interesting issue, and relevant to other SoCs, too.

In this particular case, the "canfd" clock is a core clock used as an
auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
to three scenarios:
   1. Linux controls all CAN interfaces
  => no issue,
   2. The OS on the RT CPU controls all CAN interfaces
  => issue, Linux disables the clock
   3. Mix of 1 and 2
  => More issues.
Of course this is not limited to clocks, but also to e.g. PM domains.

How can this be handled?
I believe just marking the "canfd" clock critical is not the right solution,
as about any clock could be used by the RT CPU.

Still, Linux needs to be made aware that devices (clocks and PM domains) are
controlled by another CPU/OS.

Should this be described in DT? It feels like software policy to me.

Note that we (mainline) currently don't describe the Cortex R7 core in DT.
Dirk: do you describe it?



No, we don't describe anything R7 related in DT, too.



Summary:
   1. Core/module clocks are described in the clock driver (not in DT),
   2. Unused clocks are disabled by CCF,
   3. Clocks may be in use by the Real-Time CPU core, running another OS,
   4. How to communicate to Linux which clocks are under control of the RT CPU?

>

Thanks for your comments!



While I appreciated that the overall issue is discussed, I'm not sure if 
there is anything really special we don't support generally, yet.


We have an infrastructure to mark clocks enabled anywhere else to be not 
disabled by Linux kernel (CLK_IS_CRITICAL). From my point of view, for 
this infrastructure, it doesn't matter, where this 'anywhere else' is. 
To take some concrete Renesas RCar3 examples, from my point of view it 
doesn't matter if its a GIC-400 clock enabled in the boot loader 
(U-Boot) or a CAN clock enabled by the R7. In both cases marking them as 
critical on Linux side does the trick.


The issue I just want to address (discuss) with this RFC patch is that 
for Renesas RCar3 we have CLK_IS_CRITICAL support for module clocks, but 
not for core clocks. From my point of view, this is a completely Renesas 
implementation specific discussion.


So I would rephrase the initial sentence above

"Clocks may be in use by another CPU not running Linux, while Linux 
disables them as being unused."


to anything like

"Clocks may be enabled (used) by others (U-Boot/CPUs/Hypervisors), while 
Linux disables them as being unused"


And I think this is completely addressed by CLK_IS_CRITICAL, as far as I 
can see :)


Best regards

Dirk


  drivers/clk/renesas/clk-div6.c | 17 +++--
  drivers/clk/renesas/clk-div6.h |  4 +++-
  drivers/clk/renesas/r8a7795-cpg-mssr.c |  7 +++
  drivers/clk/renesas/renesas-cpg-mssr.c |  3 ++-
  drivers/clk/renesas/renesas-cpg-mssr.h |  8 
  5 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/renesas/clk-div6.c b/drivers/clk/renesas/clk-div6.c
index 0627860..5917e05 100644
--- a/drivers/clk/renesas/clk-div6.c
+++ b/drivers/clk/renesas/clk-div6.c
@@ -18,6 +18,7 @@
  #include 
  #include 

+#include "renesas-cpg-mssr.h"
  #include "clk-div6.h"

  #define CPG_DIV6_CKSTP BIT(8)
@@ -184,7 +185,9 @@ static const struct clk_ops cpg_div6_clock_ops = {
  struct clk * __init cpg_div6_register(const char *name,
   unsigned int num_parents,
   const char **parent_names,
- void __iomem *reg)
+ void __iomem *reg,
+ const struct cpg_mssr_info *info,
+ unsigned int id)
  {
 unsigned int valid_parents;
 struct clk_init_data init;
@@ -246,6 +249,15 @@ struct clk * __init 

Clocks used by another OS/CPU (was: Re: [RFC PATCH] clk: renesas: cpg-mssr: Add interface for critical core clocks)

[Geert Uytterhoeven]

Hi Dirk,

CC clock, ARM, DT, PM people

TL;DR: Clocks may be in use by another CPU not running Linux, while Linux
disables them as being unused.

On Mon, Jun 26, 2017 at 1:30 PM, Dirk Behme  wrote:
> With commit 72f5df2c2bbb6 ("clk: renesas: cpg-mssr: Migrate to
> CLK_IS_CRITICAL") we are able to handle critical module clocks.
> Introduce the same logic for critical core clocks.
>
> Signed-off-by: Dirk Behme 
> ---
> Commit
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/clk/renesas?id=72f5df2c2bbb66d4a555cb51eb9f412abf1af77f
>
> is quite nice to avoid *module* clocks being disabled. Unfortunately,
> there are *core* clocks, too. E.g. using an other OS on the Cortex R7
> core of the r8a7795, the 'canfd' is a quite popular core clock which
> shouldn't be disabled by Linux.
>
> Therefore, this patch is a proposal to use the same 'mark clocks as
> critical' logic implemented for the module clocks for the core
> clocks, too.
>
> Opinions?

On r8a7795, there are several Cortex A cores running Linux, and a Cortex R7
core which may run another OS.
This is an interesting issue, and relevant to other SoCs, too.

In this particular case, the "canfd" clock is a core clock used as an
auxiliary clock for the CAN0, CAN1, and CANFD interfaces.  This can lead
to three scenarios:
  1. Linux controls all CAN interfaces
 => no issue,
  2. The OS on the RT CPU controls all CAN interfaces
 => issue, Linux disables the clock
  3. Mix of 1 and 2
 => More issues.
Of course this is not limited to clocks, but also to e.g. PM domains.

How can this be handled?
I believe just marking the "canfd" clock critical is not the right solution,
as about any clock could be used by the RT CPU.

Still, Linux needs to be made aware that devices (clocks and PM domains) are
controlled by another CPU/OS.

Should this be described in DT? It feels like software policy to me.

Note that we (mainline) currently don't describe the Cortex R7 core in DT.
Dirk: do you describe it?

Summary:
  1. Core/module clocks are described in the clock driver (not in DT),
  2. Unused clocks are disabled by CCF,
  3. Clocks may be in use by the Real-Time CPU core, running another OS,
  4. How to communicate to Linux which clocks are under control of the RT CPU?

Thanks for your comments!

>  drivers/clk/renesas/clk-div6.c | 17 +++--
>  drivers/clk/renesas/clk-div6.h |  4 +++-
>  drivers/clk/renesas/r8a7795-cpg-mssr.c |  7 +++
>  drivers/clk/renesas/renesas-cpg-mssr.c |  3 ++-
>  drivers/clk/renesas/renesas-cpg-mssr.h |  8 
>  5 files changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/renesas/clk-div6.c b/drivers/clk/renesas/clk-div6.c
> index 0627860..5917e05 100644
> --- a/drivers/clk/renesas/clk-div6.c
> +++ b/drivers/clk/renesas/clk-div6.c
> @@ -18,6 +18,7 @@
>  #include 
>  #include 
>
> +#include "renesas-cpg-mssr.h"
>  #include "clk-div6.h"
>
>  #define CPG_DIV6_CKSTP BIT(8)
> @@ -184,7 +185,9 @@ static const struct clk_ops cpg_div6_clock_ops = {
>  struct clk * __init cpg_div6_register(const char *name,
>   unsigned int num_parents,
>   const char **parent_names,
> - void __iomem *reg)
> + void __iomem *reg,
> + const struct cpg_mssr_info *info,
> + unsigned int id)
>  {
> unsigned int valid_parents;
> struct clk_init_data init;
> @@ -246,6 +249,15 @@ struct clk * __init cpg_div6_register(const char *name,
> init.name = name;
> init.ops = _div6_clock_ops;
> init.flags = CLK_IS_BASIC;
> +   if (info) {
> +   for (i = 0; i < info->num_crit_core_clks; i++)
> +   if (id == info->crit_core_clks[i]) {
> +   pr_devel("DIV6 %s setting CLK_IS_CRITICAL\n",
> +name);
> +   init.flags |= CLK_IS_CRITICAL;
> +   break;
> +   }
> +   }
> init.parent_names = parent_names;
> init.num_parents = valid_parents;
>
> @@ -298,7 +310,8 @@ static void __init cpg_div6_clock_init(struct device_node 
> *np)
> for (i = 0; i < num_parents; i++)
> parent_names[i] = of_clk_get_parent_name(np, i);
>
> -   clk = cpg_div6_register(clk_name, num_parents, parent_names, reg);
> +   clk = cpg_div6_register(clk_name, num_parents, parent_names, reg,
> +   NULL, 0);
> if (IS_ERR(clk)) {
> pr_err("%s: failed to register %s DIV6 clock (%ld)\n",
>__func__, np->name, PTR_ERR(clk));
> diff --git a/drivers/clk/renesas/clk-div6.h b/drivers/clk/renesas/clk-div6.h
> index 567b31d..b619d6b4