Re: [PATCH 2/2] clk: renesas: mstp: Make INTC-SYS a critical clock

[Geert Uytterhoeven]

Hi Stephen,

On Sat, Jan 21, 2017 at 12:12 AM, Stephen Boyd  wrote:
> On 01/17, Geert Uytterhoeven wrote:
>> INTC-SYS is the module clock for the GIC.  Accessing the GIC while it is
>> disabled causes:
>>
>> Unhandled fault: asynchronous external abort (0x1211) at 0x
>>
>> Currently, the GIC-400 driver cannot enable its module clock for several
>> reasons:
>>   - It does not use a platform device, so Runtime PM is not an option,
>>   - gic_of_init() runs before any clocks are registered, so it cannot
>> enable the clock explicitly,
>>   - gic_of_init() cannot return -EPROBE_DEFER, as IRQCHIP_DECLARE()
>> doesn't support deferred probing.
>>
>> Hence we have to keep on relying on the boot loader for enabling the
>> module clock.
>>
>> To prevent the module clock from being disabled when the CCF core thinks
>> it is unused, and thus causing a system lock-up, add a check to the MSTP
>> clock driver and enable CLK_IS_CRITICAL. This will make sure the module
>> clock is never disabled.
>>
>> This is a hard dependency for describing the INTC-SYS clock in DT on
>> R-Mobile APE6 and R-Car Gen2.
>>
>> Signed-off-by: Geert Uytterhoeven 
>> ---
>
> Acked-by: Stephen Boyd 

Thanks!

>> diff --git a/drivers/clk/renesas/clk-mstp.c b/drivers/clk/renesas/clk-mstp.c
>> index 937576d99407..c0319b8acf3521a2 100644
>> --- a/drivers/clk/renesas/clk-mstp.c
>> +++ b/drivers/clk/renesas/clk-mstp.c
>> @@ -144,6 +144,11 @@ static int cpg_mstp_clock_is_enabled(struct clk_hw *hw)
>
> Sad that git gets confused about which function this is in.

Indeed. Will send a patch to fix that...

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: [PATCH 2/2] clk: renesas: mstp: Make INTC-SYS a critical clock

[Stephen Boyd]

On 01/17, Geert Uytterhoeven wrote:
> INTC-SYS is the module clock for the GIC.  Accessing the GIC while it is
> disabled causes:
> 
> Unhandled fault: asynchronous external abort (0x1211) at 0x
> 
> Currently, the GIC-400 driver cannot enable its module clock for several
> reasons:
>   - It does not use a platform device, so Runtime PM is not an option,
>   - gic_of_init() runs before any clocks are registered, so it cannot
> enable the clock explicitly,
>   - gic_of_init() cannot return -EPROBE_DEFER, as IRQCHIP_DECLARE()
> doesn't support deferred probing.
> 
> Hence we have to keep on relying on the boot loader for enabling the
> module clock.
> 
> To prevent the module clock from being disabled when the CCF core thinks
> it is unused, and thus causing a system lock-up, add a check to the MSTP
> clock driver and enable CLK_IS_CRITICAL. This will make sure the module
> clock is never disabled.
> 
> This is a hard dependency for describing the INTC-SYS clock in DT on
> R-Mobile APE6 and R-Car Gen2.
> 
> Signed-off-by: Geert Uytterhoeven 
> ---

Acked-by: Stephen Boyd 

> diff --git a/drivers/clk/renesas/clk-mstp.c b/drivers/clk/renesas/clk-mstp.c
> index 937576d99407..c0319b8acf3521a2 100644
> --- a/drivers/clk/renesas/clk-mstp.c
> +++ b/drivers/clk/renesas/clk-mstp.c
> @@ -144,6 +144,11 @@ static int cpg_mstp_clock_is_enabled(struct clk_hw *hw)

Sad that git gets confused about which function this is in.

>   init.name = name;
>   init.ops = _mstp_clock_ops;
>   init.flags = CLK_IS_BASIC | CLK_SET_RATE_PARENT;
> + /* INTC-SYS is the module clock of the GIC, and must not be disabled */
> + if (!strcmp(name, "intc-sys")) {
> + pr_debug("MSTP %s setting CLK_IS_CRITICAL\n", name);
> + init.flags |= CLK_IS_CRITICAL;
> + }
>   init.parent_names = _name;
>   init.num_parents = 1;
>  

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