The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 660b299bed2a2a55a1f9102d029549d0235f881c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025112439-squealing-sixties-951d@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 660b299bed2a2a55a1f9102d029549d0235f881c Mon Sep 17 00:00:00 2001 From: Diogo Ivo diogo.ivo@tecnico.ulisboa.pt Date: Mon, 3 Nov 2025 14:14:15 +0000 Subject: [PATCH] Revert "drm/tegra: dsi: Clear enable register if powered by bootloader"

Commit b6bcbce33596 ("soc/tegra: pmc: Ensure power-domains are in a known state") was introduced so that all power domains get initialized to a known working state when booting and it does this by shutting them down (including asserting resets and disabling clocks) before registering each power domain with the genpd framework, leaving it to each driver to later on power its needed domains.

This caused the Google Pixel C to hang when booting due to a workaround in the DSI driver introduced in commit b22fd0b9639e ("drm/tegra: dsi: Clear enable register if powered by bootloader") meant to handle the case where the bootloader enabled the DSI hardware module. The workaround relies on reading a hardware register to determine the current status and after b6bcbce33596 that now happens in a powered down state thus leading to the boot hang.

Fix this by reverting b22fd0b9639e since currently we are guaranteed that the hardware will be fully reset by the time we start enabling the DSI module.

Fixes: b6bcbce33596 ("soc/tegra: pmc: Ensure power-domains are in a known state") Cc: stable@vger.kernel.org Signed-off-by: Diogo Ivo diogo.ivo@tecnico.ulisboa.pt Signed-off-by: Thierry Reding treding@nvidia.com Link: https://patch.msgid.link/20251103-diogo-smaug_ec_typec-v1-1-be656ccda391@tec...

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c index b5089b772267..ddfb2858acbf 100644 --- a/drivers/gpu/drm/tegra/dsi.c +++ b/drivers/gpu/drm/tegra/dsi.c @@ -913,15 +913,6 @@ static void tegra_dsi_encoder_enable(struct drm_encoder *encoder) u32 value; int err;

- /* If the bootloader enabled DSI it needs to be disabled - * in order for the panel initialization commands to be - * properly sent. - */ - value = tegra_dsi_readl(dsi, DSI_POWER_CONTROL); - - if (value & DSI_POWER_CONTROL_ENABLE) - tegra_dsi_disable(dsi); - err = tegra_dsi_prepare(dsi); if (err < 0) { dev_err(dsi->dev, "failed to prepare: %d\n", err);