Re: [PATCH v2 0/3] PM / Domain: renesas: Fix active wakeup behavior

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Ulf,

On Fri, Nov 10, 2017 at 10:57 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 9 November 2017 at 14:26, Geert Uytterhoeven <geert+renesas@glider.be> wrote:
>> If a device in a Renesas ARM SoC is part of a Clock Domain, and it is
>> used as a wakeup source, it must be kept active during system suspend.
>
> Geert, I think we discussed this a bit already. I wonder if the above
> is a correct statement for all devices in these PM domains, that has
> wakeups?

It is true for all wakeup sources (e.g. Ethernet and serial).

> Don't these SoCs make use of any external logic (out-of-band IRQ) to
> deal with the wakeup IRQs?
>
> For example, how is GPIO irqs dealt with in this regards?

Interrupt controllers (incl. GPIO) may, depending on SoC type:
  - be located in a controllable power area (SH/R-Mobile),
  - may run from a controllable module clock (SH/R-Mobile, R-Car Gen2/Gen3,
    RZ/A1, RZ/G1).

So there are no out-of-band IRQs in the wakeup path, unless on SoCs where
the interrupt controllers are in an always-on power area, AND run from a
fixed clock. I think only R-Car Gen1 falls in that category.
Still, R-Car Gen1 needs active_wakeup for wakeup sources.

See series "[PATCH/RFC 0/3] renesas: irqchip: Use wakeup_path i.s.o.
explicit clock handling", which includes GPIO interrupts.

> If that is the case, you should really avoid using the big hammer
> method of setting the GENPD_FLAG_ACTIVE_WAKEUP.

So I think I do need the big hammer ;-)

>> Currently this is handled in device-specific drivers by explicitly
>> increasing the use count of the module clock when the device is
>> configured as a wakeup source, or if it is part of the wakeup path.
>>
>> However, this is merely a workaround.  The proper way to prevent the
>> device from being stopped is to inform this requirement to the genpd
>> core, using the new GENPD_FLAG_ACTIVE_WAKEUP flag introduced in commit
>> 95a20ef6f7e54c6a ("PM / Domains: Allow genpd users to specify default
>> active wakeup behavior").
>>
>> Hence this series does that for PM Domain drivers used on R-Car, RZ/A1,
>> RZ/G1 SoCs, mimicking what is already done succesfully on SH/R-Mobile
>> SoCs.  This will allow for the workarounds can be removed later.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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