Re: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Ulf Hansson]

On 26 January 2017 at 15:39, Rob Herring  wrote:
> On Mon, Jan 23, 2017 at 11:56 AM, Chris Brandt  
> wrote:
>> Hello Rob,
>>
>>
>> On Monday, January 23, 2017, Rob Herring wrote:
>>> > --- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
>>> > +++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
>>> > @@ -25,8 +25,32 @@ Required properties:
>>> > "renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
>>> > "renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
>>> >
>>> > +- clocks: Most controllers only have 1 clock source per channel.
>>> However, on
>>> > + some variations of this controller, the internal card detection
>>>
>>> This should be explicit as to which compatible strings have 2 clocks and
>>> which have 1 clock.
>>
>> OK. I'll make a list like I did for sh_mmcif:
>>
>> https://patchwork.kernel.org/patch/9512091/
>>
>>
>>
>>> > +
>>> > +Example showing 2 clocks:
>>> > +   sdhi0: sd@e804e000 {
>>>
>>> mmc@...
>>
>> I'm confused. I see that for all SDHI controllers, it either "sd@" or 
>> "sdhci@".
>>
>> $ grep sdhi $(find arch/arm/boot/dts -name "*.dtsi")
>>
>> $ grep sdhci $(find arch/arm/boot/dts -name "*.dtsi")
>
> Yes, there's lots of variation. Node names are supposed to be generic
> for their class of device (e.g. ethernet, pci, usb,
> interrupt-controller, etc.). I'd be fine with "sd", but think "mmc" is
> more common. Either way, we should pick one moving forward. "sdhci"
> should not be used as that's a specific implementation.

I think we discussed this earlier. The problem with these devices is
that it covers several type of devices, so it's hard to find a generic
node name.

The devices are: MMC, eMMC, SD, SDIO. I don't have strong opinions on
whether to chose a generic node name, and perhaps "mmc" is the best we
can get?

Whatever we decide, we should update all mmc DTS docs, to avoid future
confusion.

Kind regards
Uffe

RE: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Chris Brandt]

On Thursday, January 26, 2017, Rob Herring wrote:
> >> > +
> >> > +Example showing 2 clocks:
> >> > +   sdhi0: sd@e804e000 {
> >>
> >> mmc@...
> >
> > I'm confused. I see that for all SDHI controllers, it either "sd@" or
> "sdhci@".
> >
> > $ grep sdhi $(find arch/arm/boot/dts -name "*.dtsi")
> >
> > $ grep sdhci $(find arch/arm/boot/dts -name "*.dtsi")
> 
> Yes, there's lots of variation. Node names are supposed to be generic for
> their class of device (e.g. ethernet, pci, usb, interrupt-controller,
> etc.). I'd be fine with "sd", but think "mmc" is more common. Either way,
> we should pick one moving forward. "sdhci"
> should not be used as that's a specific implementation.
> 
> Rob

For now, I took the example back out of tmio_mmc.txt since I figured
people can refer back to mmc.txt for what the naming should be (since
the directory name is mmc, you would think the golden rules were in
mmc.txt)


> I'd be fine with "sd", but think "mmc" is more common.

NOTE: mmc.txt currently has 2 examples:

sdhci@ab00 {

mmc3: mmc@01c12000 {

Chris

Re: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Rob Herring]

On Mon, Jan 23, 2017 at 11:56 AM, Chris Brandt  wrote:
> Hello Rob,
>
>
> On Monday, January 23, 2017, Rob Herring wrote:
>> > --- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
>> > +++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
>> > @@ -25,8 +25,32 @@ Required properties:
>> > "renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
>> > "renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
>> >
>> > +- clocks: Most controllers only have 1 clock source per channel.
>> However, on
>> > + some variations of this controller, the internal card detection
>>
>> This should be explicit as to which compatible strings have 2 clocks and
>> which have 1 clock.
>
> OK. I'll make a list like I did for sh_mmcif:
>
> https://patchwork.kernel.org/patch/9512091/
>
>
>
>> > +
>> > +Example showing 2 clocks:
>> > +   sdhi0: sd@e804e000 {
>>
>> mmc@...
>
> I'm confused. I see that for all SDHI controllers, it either "sd@" or 
> "sdhci@".
>
> $ grep sdhi $(find arch/arm/boot/dts -name "*.dtsi")
>
> $ grep sdhci $(find arch/arm/boot/dts -name "*.dtsi")

Yes, there's lots of variation. Node names are supposed to be generic
for their class of device (e.g. ethernet, pci, usb,
interrupt-controller, etc.). I'd be fine with "sd", but think "mmc" is
more common. Either way, we should pick one moving forward. "sdhci"
should not be used as that's a specific implementation.

Rob

RE: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Chris Brandt]

Hello Rob,


On Monday, January 23, 2017, Rob Herring wrote:
> > --- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
> > +++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
> > @@ -25,8 +25,32 @@ Required properties:
> > "renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
> > "renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
> >
> > +- clocks: Most controllers only have 1 clock source per channel.
> However, on
> > + some variations of this controller, the internal card detection
> 
> This should be explicit as to which compatible strings have 2 clocks and
> which have 1 clock.

OK. I'll make a list like I did for sh_mmcif:

https://patchwork.kernel.org/patch/9512091/



> > +
> > +Example showing 2 clocks:
> > +   sdhi0: sd@e804e000 {
> 
> mmc@...

I'm confused. I see that for all SDHI controllers, it either "sd@" or "sdhci@".

$ grep sdhi $(find arch/arm/boot/dts -name "*.dtsi")

$ grep sdhci $(find arch/arm/boot/dts -name "*.dtsi")


Regards,
Chris

Re: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Rob Herring]

On Fri, Jan 20, 2017 at 10:06:03PM -0500, Chris Brandt wrote:
> In the case of a single clock source, you don't need names. However,
> if the controller has 2 clock sources, you need to name them correctly
> so the driver can find the 2nd one. The 2nd clock is for the internal
> card detect logic.
> 
> Signed-off-by: Chris Brandt 
> ---
> v4:
> * just explain there might be 2 clocks, don't explain how
>   we will use them in the driver
> v3:
> * add more clarification about why there are sometimes 2 clocks
>   and what you should do with them.
> * remove 'status = "disabled"' from example
> v2:
> * fix spelling and change wording
> * changed clock name from "carddetect" to "cd"
> ---
>  Documentation/devicetree/bindings/mmc/tmio_mmc.txt | 24 
> ++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt 
> b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
> index a1650ed..1464c16 100644
> --- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
> +++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
> @@ -25,8 +25,32 @@ Required properties:
>   "renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
>   "renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
>  
> +- clocks: Most controllers only have 1 clock source per channel. However, on
> +   some variations of this controller, the internal card detection

This should be explicit as to which compatible strings have 2 clocks and 
which have 1 clock.

> +   logic that exists in this controller is sectioned off to be run by a
> +   separate second clock source to allow the main core clock to be turned
> +   off to save power.
> +   If 2 clocks are specified by the hardware, you must name them as
> +   "core" and "cd".
> +   If the controller only has 1 clock, naming is not required.
> +
>  Optional properties:
>  - toshiba,mmc-wrprotect-disable: write-protect detection is unavailable
>  - pinctrl-names: should be "default", "state_uhs"
>  - pinctrl-0: should contain default/high speed pin ctrl
>  - pinctrl-1: should contain uhs mode pin ctrl
> +
> +Example showing 2 clocks:
> + sdhi0: sd@e804e000 {

mmc@...

> + compatible = "renesas,sdhi-r7s72100";
> + reg = <0xe804e000 0x100>;
> + interrupts =  +   GIC_SPI 271 IRQ_TYPE_LEVEL_HIGH
> +   GIC_SPI 272 IRQ_TYPE_LEVEL_HIGH>;
> +
> + clocks = <_clks R7S72100_CLK_SDHI00>,
> +  <_clks R7S72100_CLK_SDHI01>;
> + clock-names = "core", "cd";
> + cap-sd-highspeed;
> + cap-sdio-irq;
> + };
> -- 
> 2.10.1
> 
> 

Re: [PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Wolfram Sang]

On Fri, Jan 20, 2017 at 10:06:03PM -0500, Chris Brandt wrote:
> In the case of a single clock source, you don't need names. However,
> if the controller has 2 clock sources, you need to name them correctly
> so the driver can find the 2nd one. The 2nd clock is for the internal
> card detect logic.
> 
> Signed-off-by: Chris Brandt 

Reviewed-by: Wolfram Sang 



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[PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Chris Brandt]

In the case of a single clock source, you don't need names. However,
if the controller has 2 clock sources, you need to name them correctly
so the driver can find the 2nd one. The 2nd clock is for the internal
card detect logic.

Signed-off-by: Chris Brandt 
---
v4:
* just explain there might be 2 clocks, don't explain how
  we will use them in the driver
v3:
* add more clarification about why there are sometimes 2 clocks
  and what you should do with them.
* remove 'status = "disabled"' from example
v2:
* fix spelling and change wording
* changed clock name from "carddetect" to "cd"
---
 Documentation/devicetree/bindings/mmc/tmio_mmc.txt | 24 ++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt 
b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
index a1650ed..1464c16 100644
--- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
@@ -25,8 +25,32 @@ Required properties:
"renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
"renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
 
+- clocks: Most controllers only have 1 clock source per channel. However, on
+ some variations of this controller, the internal card detection
+ logic that exists in this controller is sectioned off to be run by a
+ separate second clock source to allow the main core clock to be turned
+ off to save power.
+ If 2 clocks are specified by the hardware, you must name them as
+ "core" and "cd".
+ If the controller only has 1 clock, naming is not required.
+
 Optional properties:
 - toshiba,mmc-wrprotect-disable: write-protect detection is unavailable
 - pinctrl-names: should be "default", "state_uhs"
 - pinctrl-0: should contain default/high speed pin ctrl
 - pinctrl-1: should contain uhs mode pin ctrl
+
+Example showing 2 clocks:
+   sdhi0: sd@e804e000 {
+   compatible = "renesas,sdhi-r7s72100";
+   reg = <0xe804e000 0x100>;
+   interrupts = ;
+
+   clocks = <_clks R7S72100_CLK_SDHI00>,
+<_clks R7S72100_CLK_SDHI01>;
+   clock-names = "core", "cd";
+   cap-sd-highspeed;
+   cap-sdio-irq;
+   };
-- 
2.10.1