FAILED: patch "[PATCH] drm/i915: Pick the backlight controller based on VBT on ICP+" failed to apply to 6.2-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.2-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-6.2.y
git checkout FETCH_HEAD
git cherry-pick -x b33771546309b46b681388b3540b69a75a0e2e69
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023051317-cough-appetite-8a92@gregkh' --subject-prefix 'PATCH 6.2.y' HEAD^..

Possible dependencies:

b33771546309 ("drm/i915: Pick the backlight controller based on VBT on ICP+")

thanks,

greg k-h

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

From b33771546309b46b681388b3540b69a75a0e2e69 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Tue, 7 Feb 2023 08:43:37 +0200
Subject: [PATCH] drm/i915: Pick the backlight controller based on VBT on ICP+
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Use the second backlight controller on ICP+ if the VBT asks
us to do so.

On pre-MTP we also check the chicken bit to make sure the
pins have been correctly muxed by the firmware.

Cc: stable@vger.kernel.org
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8016
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230207064337.18697-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
index 5b7da72c95b8..a4e4b7f79e4d 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1431,6 +1431,30 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
 	return 0;
 }
 
+static int cnp_num_backlight_controllers(struct drm_i915_private *i915)
+{
+	if (INTEL_PCH_TYPE(i915) >= PCH_DG1)
+		return 1;
+
+	if (INTEL_PCH_TYPE(i915) >= PCH_ICP)
+		return 2;
+
+	return 1;
+}
+
+static bool cnp_backlight_controller_is_valid(struct drm_i915_private *i915, int controller)
+{
+	if (controller < 0 || controller >= cnp_num_backlight_controllers(i915))
+		return false;
+
+	if (controller == 1 &&
+	    INTEL_PCH_TYPE(i915) >= PCH_ICP &&
+	    INTEL_PCH_TYPE(i915) < PCH_MTP)
+		return intel_de_read(i915, SOUTH_CHICKEN1) & ICP_SECOND_PPS_IO_SELECT;
+
+	return true;
+}
+
 static int
 cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
 {
@@ -1440,10 +1464,14 @@ cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
 
 	/*
 	 * CNP has the BXT implementation of backlight, but with only one
-	 * controller. TODO: ICP has multiple controllers but we only use
-	 * controller 0 for now.
+	 * controller. ICP+ can have two controllers, depending on pin muxing.
 	 */
-	panel->backlight.controller = 0;
+	panel->backlight.controller = connector->panel.vbt.backlight.controller;
+	if (!cnp_backlight_controller_is_valid(i915, panel->backlight.controller)) {
+		drm_dbg_kms(&i915->drm, "Invalid backlight controller %d, assuming 0\n",
+			    panel->backlight.controller);
+		panel->backlight.controller = 0;
+	}
 
 	pwm_ctl = intel_de_read(i915,
 				BXT_BLC_PWM_CTL(panel->backlight.controller));