From: Thierry Reding <thierry.reding@gmail.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Wolfram Sang <wsa@the-dreams.de>,
Jon Hunter <jonathanh@nvidia.com>,
linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org
Subject: Re: [PATCH 2/5] i2c: tegra: Restore pinmux on system resume
Date: Tue, 19 May 2020 17:57:28 +0200 [thread overview]
Message-ID: <20200519155728.GA2113674@ulmo> (raw)
In-Reply-To: <f149bb64-e93b-364e-47bc-c851e9638a35@gmail.com>
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On Fri, May 08, 2020 at 06:00:57PM +0300, Dmitry Osipenko wrote:
> 08.05.2020 13:31, Thierry Reding пишет:
> ...
> >> Is it legal to touch DPAUX registers while DPAUX is in a suspended state?
> >
> > DPAUX is never runtime suspended and the dependency from the I2C
> > controller on DPAUX should ensure that they are suspended and resumed in
> > the right order during system sleep.
>
> 1. Could you please explain why DPAUX is never suspended? Isn't it a
> problem?
>
> It looks a bit odd that driver is doing this [1][2]. RPM is supposed to
> be used for the *dynamic* power management. Should we remove RPM usage
> from the DPAUX driver?
>
> [1]
> https://elixir.bootlin.com/linux/v5.7-rc4/source/drivers/gpu/drm/tegra/dpaux.c#L524
> [2]
> https://elixir.bootlin.com/linux/v5.7-rc4/source/drivers/gpu/drm/tegra/dpaux.c#L591
Looks more like the intention had been to eventually enable dynamic
power management but I never got around to it. The runtime PM
implementations are what's necessary to runtime suspend the device,
so all that should be needed is hook up the pm_runtime_get() and
pm_runtime_put() calls correctly.
> 2. Could you please explain why I2C driver has to care about restoring
> the pinmux state? Why pinctrl driver isn't doing that for I2C and
> everything else?
We could probably do it either way. I did it this way because the
runtime suspend/resume will get called either way, so might as well
reuse the same code paths rather than add context save/restore.
Thierry
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next prev parent reply other threads:[~2020-05-19 15:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 19:33 [PATCH 0/5] i2c: tegra: Various fixes and improvements Thierry Reding
2020-05-06 19:33 ` [PATCH 1/5] Revert "i2c: tegra: Fix suspending in active runtime PM state" Thierry Reding
2020-05-06 19:33 ` [PATCH 2/5] i2c: tegra: Restore pinmux on system resume Thierry Reding
2020-05-06 22:43 ` mirq-test
2020-05-07 10:03 ` Thierry Reding
2020-05-07 12:20 ` Michał Mirosław
2020-05-07 21:50 ` Dmitry Osipenko
2020-05-08 10:31 ` Thierry Reding
2020-05-08 15:00 ` Dmitry Osipenko
2020-05-09 15:35 ` Dmitry Osipenko
2020-05-19 16:07 ` Thierry Reding
2020-05-19 15:57 ` Thierry Reding [this message]
2020-05-08 15:05 ` Dmitry Osipenko
2020-05-06 19:33 ` [PATCH 3/5] i2c: tegra: Keep IRQs enabled during suspend/resume Thierry Reding
2020-05-06 19:33 ` [PATCH 4/5] i2c: tegra: Better handle case where CPU0 is busy for a long time Thierry Reding
2020-05-06 19:33 ` [PATCH 5/5] i2c: tegra: Synchronize DMA before termination Thierry Reding
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