Revert "drm/tegra: dsi: Clear enable register if powered by bootloader"

Commit b6bcbce ("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 b22fd0b ("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
b6bcbce that now happens in a powered down state thus leading to
the boot hang.

Fix this by reverting b22fd0b since currently we are guaranteed
that the hardware will be fully reset by the time we start enabling the
DSI module.

Fixes: b6bcbce ("soc/tegra: pmc: Ensure power-domains are in a known state")
Cc: [email protected]
Signed-off-by: Diogo Ivo <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>
Link: https://patch.msgid.link/20251103-diogo-smaug_ec_typec-v1-1-be656ccda391@tecnico.ulisboa.pt

Author: diogoivo

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);