[PATCH 0/2] drm/tegra: Fix panel support on Venice 2 and Nyan

From: Thierry Reding <thierry.reding@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Thomas Graichen <thomas.graichen@gmail.com>,
	Douglas Anderson <dianders@chromium.org>,
	dri-devel@lists.freedesktop.org,
	Jon Hunter <jonathanh@nvidia.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	linux-tegra@vger.kernel.org, Dmitry Osipenko <digetx@gmail.com>
Subject: [PATCH 0/2] drm/tegra: Fix panel support on Venice 2 and Nyan
Date: Mon, 20 Dec 2021 11:48:53 +0100	[thread overview]
Message-ID: <20211220104855.428290-1-thierry.reding@gmail.com> (raw)

From: Thierry Reding <treding@nvidia.com>

Hi,

this is an alternative proposal to fix panel support on Venice 2 and
Nyan. Dmitry had proposed a different solution that involved reverting
the I2C/DDC registration order and would complicate things by breaking
the encapsulation of the driver by introducing a global (though locally
scoped) variable[0].

This set of patches avoids that by using the recently introduced DP AUX
bus infrastructure. The result is that the changes are actually less
intrusive and not a step back. Instead they nicely remove the circular
dependency that previously existed and caused these issues in the first
place.

To be fair, this is not perfect either because it requires a device tree
change and hence isn't technically backwards-compatible. However, given
that the original device tree was badly broken in the first place, I
think we can make an exception, especially since it is not generally a
problem to update device trees on the affected devices.

Secondly, this relies on infrastructure that was introduced in v5.15 and
therefore will be difficult to backport beyond that. However, since this
functionality has been broken since v5.13 and all of the kernel versions
between that and v5.15 are EOL anyway, there isn't much that we can do
to fix the interim versions anyway.

Adding Doug and Laurent since they originally designed the AUX bus
patches in case they see anything in here that would be objectionable.

Thierry

[0]: https://lore.kernel.org/dri-devel/20211130230957.30213-1-digetx@gmail.com/

Thierry Reding (2):
  drm/tegra: dpaux: Populate AUX bus
  ARM: tegra: Move panels to AUX bus

 arch/arm/boot/dts/tegra124-nyan-big.dts   | 15 +++++++++------
 arch/arm/boot/dts/tegra124-nyan-blaze.dts | 15 +++++++++------
 arch/arm/boot/dts/tegra124-venice2.dts    | 14 +++++++-------
 drivers/gpu/drm/tegra/Kconfig             |  1 +
 drivers/gpu/drm/tegra/dpaux.c             |  7 +++++++
 5 files changed, 33 insertions(+), 19 deletions(-)

-- 
2.34.1