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From: Dmitry Osipenko <digetx@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-tegra@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	dri-devel@lists.freedesktop.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 2/2] drm/tegra: Do not implement runtime PM
Date: Wed, 4 Dec 2019 18:22:19 +0300
Message-ID: <3d2b4fed-d2e6-bb4a-c94b-d493ba836661@gmail.com> (raw)
In-Reply-To: <20191203162733.1436800-2-thierry.reding@gmail.com>

03.12.2019 19:27, Thierry Reding пишет:
> From: Thierry Reding <treding@nvidia.com>
> 
> The Tegra DRM driver heavily relies on the implementations for runtime
> suspend/resume to be called at specific times. Unfortunately, there are
> some cases where that doesn't work. One example is if the user disables
> runtime PM for a given subdevice. Another example is that the PM core
> acquires a reference to runtime PM during system sleep, effectively
> preventing devices from going into low power modes. This is intentional
> to avoid nasty race conditions, but it also causes system sleep to not
> function properly on all Tegra systems.
> 
> Fix this by not implementing runtime PM at all. Instead, a minimal,
> reference-counted suspend/resume infrastructure is added to the host1x
> bus. This has the benefit that it can be used regardless of the system
> power state (or any transitions we might be in), or whether or not the
> user allows runtime PM.
> 
> Atomic modesetting guarantees that these functions will end up being
> called at the right point in time, so the pitfalls for the more generic
> runtime PM do not apply here.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---

Couldn't we just use pm_runtime_force_suspend/resume whenever it is
necessary to enforce the suspend/resume?

I briefly looked through the previous discussion and don't see why the
forced suspend/resume isn't suitable. Please excuse me if I'm missing
the point.

Why planes/outputs need to care about resuming DC controller at all?
Doesn't DRM core take care of enabling DC for us by enabling CRTC before
planes/outputs are enabled?

      parent reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-03 16:27 [PATCH 1/2] gpu: host1x: Rename "parent" to "host" Thierry Reding
2019-12-03 16:27 ` [PATCH 2/2] drm/tegra: Do not implement runtime PM Thierry Reding
2019-12-04  8:37   ` Mikko Perttunen
2019-12-04  9:36     ` Thierry Reding
2019-12-04 15:22   ` Dmitry Osipenko [this message]

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