Hi Stephen,
On Sat, Jan 21, 2017 at 12:00 AM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
> On 01/17, Geert Uytterhoeven wrote:
>> This patch series adds support for the CLK_IS_CRITICAL flag to drivers
>> for module clocks on Renesas ARM SoCs. For now, this is used to prevent
>> disabling of the ARM GIC module clock, which would lead to a system
>> lock-up when accessing the GIC's registers.
>>
>> 1. The first patch migrates the Renesas CPG/MSSR driver from the
>> never merged CLK_ENABLE_HAND_OFF flag to the CLK_IS_CRITICAL flag.
>> Note that as the driver already handled critical clocks (i.e. it
>> ignored them :-), this is not a prerequisite for linking the GIC to
>> its module clock in DT.
>>
>> 2. The second patch makes sure the CLK_IS_CRITICAL flag is set for the
>> INTC-SYS clock on SoCs not (yet) using the Renesas CPG/MSSR driver.
>> Note that this is a hard dependency for describing the INTC-SYS
>> clock in DT on R-Mobile APE6 and R-Car Gen2.
>>
>> I plan to queue these patches in my clk-renesas-for-v4.11 branch, if
>> you agree.
>
> Would the runtime PM patches for ccf make things any better here?
It won't make much of a difference, as typically you'll want the GIC running
all the time anyway, also for wake-up sources.
We just have to make sure it's not disabled indefinitely.
As such it's different from a real critical clock that kills the system
immediately (e.g. some secret core clock): you can disable the GIC clock,
just make sure to enable it again (and have a means to re-enable it, without
relying on interrupts ;-)
The only difference with a real critical clock is that you
> I still plan to support CLK_ENABLE_HAND_OFF somehow, but it's not
> at the top of my priority list right now.
Good, we can convert back later, perhaps when the GIC driver is ready to
support PM for non-secondary GICs...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
