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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Mon, 15 Jan 2018 17:17:16 +0100
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Subject: Re: [PATCH 0/2] PM / core: genpd fix and pm_runtime_force_suspend|resume()
 rework
To: Ulf Hansson <ulf.hansson@linaro.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux PM <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>
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On Mon, Jan 15, 2018 at 3:26 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 15 January 2018 at 14:22, Geert Uytterhoeven <geert@linux-m68k.org> wrote:

[cut]

>>
>> I did miss a small difference in topology: in pm/linux-next, H3 has DMA
>> enabled for SCIF2, while M3 hasn't (yet).
>> With DMA enabled on M3, it fails in the same way.
>>
>> As genpd_resume_noirq() no longer calls pm_runtime_force_resume(),
>> rcar_dmac_runtime_resume() is no longer called, and the DMAC's registers
>> are no longer reinitialized after system resume, breaking the serial port.
>
> In drivers/dma/sh/rcar-dmac.c, I would try to replace the below line:
> SET_SYSTEM_SLEEP_PM_OPS(rcar_dmac_sleep_suspend, rcar_dmac_sleep_resume)
>
> with:
> SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)

Yes, that probably is the least intrusive thing that can be done to
address the issue.

> in case that may be too early to suspend the dma device (which is
> rather common for dma devices) then try;
>
> SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)

Good suggestion, and I would go straight for it anyway.

Geert, can you try if this works, please?

Thanks,
Rafael