3.13 i915 brightness settings broken when going from docked -> undocked

[Josh Boyer]

On Thu, Feb 20, 2014 at 07:31:41PM -0500, Josh Boyer wrote:
>On Wed, Feb 19, 2014 at 9:20 PM, Josh Boyer <jwboyer at fedoraproject.org> wrote:
>> Hi All,
>>
>> We've had a rather weird report[1] of the brightness adjustments being
>> broken in a specific case with Thinkpad x220 hardware (SandyBridge
>> based).  If you boot the machine with it in a dock and then undock,
>> the brightness adjustments do not work.  That is with either the FN
>> keys or the GNOME brightness slider.
>>
>> I can see that the value of
>> /sys/class/backlight/acpi_video0/brightness increases/decreases but
>> /sys/class/backlight/intel_backlight/brightness doesn't reflect any
>> changes.  With 3.12 this works, and oddly with 3.14-rc1 it works
>> (specifically, it starts working around v3.13-10231-g53d8ab2 which is
>> right after the first DRM merge for 3.14).  With 3.13, if I undock and
>> echo a higher value in the intel_backlight_brightness sysfs entry, the
>> brightness will actually increase so it can be done manually, but it
>> does not work as you'd expect.
>>
>> I'm in the middle of trying to do a reverse bisect for which patch
>> fixes it in the 3.14-rcX series, but that's taking a while.  I thought
>> I'd email and see if anyone already knows about this situation, what
>> patch in 3.13 broke this, and which one then fixed it again.  Thus far
>> all I've gathered is that backlight handling is confusing.
>
>The reverse bisect between 3.13 and 3.14-rc1 didn't prove fruitful,
>either because I messed it up or there's a combination of things that
>fix the issue.  So instead I did a regular git bisect between 3.12 and
>3.13 to see which commit _broke_ things and caused the above behavior.
> That landed me at:
>
>Author: Jesse Barnes <jbarnes at virtuousgeek.org>
>Date:   Thu Oct 31 18:55:49 2013 +0200
>
>    drm/i915: make backlight functions take a connector
>
>I have no idea if that makes sense or not, but it's at least something
>that seems to be in a relevant area of code.  Does anyone involved in
>that know why it would cause the above symptoms on 3.13, and which
>commit(s) fix it in 3.14-rc1?

Since nobody is replying I poked around a bit myself.  The one commit
that looks somewhat relevant in 3.14-rc1 seems to be:

commit c91c9f32843a1b433de5a1ead4789a6bc8d3d914
Author: Jani Nikula <jani.nikula at intel.com>
Date:   Fri Nov 8 16:48:55 2013 +0200

    drm/i915: make asle notifications update backlight on all connectors

That doesn't apply cleanly on 3.13 because of the other reworks that
went in first, so I came up with the patch below.  It seems to fix it
for my machine, but I'm waiting for confirmation from the original bug
reporter still.  Maybe this will elicit some comments?

josh

Backport of upstream commit c91c9f328

---
 drivers/gpu/drm/i915/i915_drv.h       |  1 +
 drivers/gpu/drm/i915/intel_opregion.c | 31 ++++++-------------------------
 drivers/gpu/drm/i915/intel_panel.c    |  4 ++++
 3 files changed, 11 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 221ac62..d6d4349 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1371,6 +1371,7 @@ typedef struct drm_i915_private {
 
 	/* backlight */
 	struct {
+		bool present;
 		int level;
 		bool enabled;
 		spinlock_t lock; /* bl registers and the above bl fields */
diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 6d69a9b..b2a51ae 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -414,38 +414,19 @@ static u32 asle_set_backlight(struct drm_device *dev, u32 bclp)
 		return ASLC_BACKLIGHT_FAILED;
 
 	mutex_lock(&dev->mode_config.mutex);
-	/*
-	 * Could match the OpRegion connector here instead, but we'd also need
-	 * to verify the connector could handle a backlight call.
-	 */
-	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
-		if (encoder->crtc == crtc) {
-			found = true;
-			break;
-		}
-
-	if (!found) {
-		ret = ASLC_BACKLIGHT_FAILED;
-		goto out;
-	}
 
-	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
-		if (connector->encoder == encoder)
-			intel_connector = to_intel_connector(connector);
-
-	if (!intel_connector) {
-		ret = ASLC_BACKLIGHT_FAILED;
-		goto out;
+	DRM_DEBUG_KMS("updating opregion backlight %d/255\n", bclp);
+	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
+		intel_connector = to_intel_connector(connector);
+		if (dev_priv->backlight.present)
+			intel_panel_set_backlight(intel_connector, bclp, 255);
 	}
 
-	DRM_DEBUG_KMS("updating opregion backlight %d/255\n", bclp);
-	intel_panel_set_backlight(intel_connector, bclp, 255);
 	iowrite32(DIV_ROUND_UP(bclp * 100, 255) | ASLE_CBLV_VALID, &asle->cblv);
 
-out:
 	mutex_unlock(&dev->mode_config.mutex);
 
-	return ret;
+	return 0;
 }
 
 static u32 asle_set_als_illum(struct drm_device *dev, u32 alsi)
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index e6f782d..fa7b984 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -832,6 +832,9 @@ int intel_panel_setup_backlight(struct drm_connector *connector)
 		dev_priv->backlight.device = NULL;
 		return -ENODEV;
 	}
+
+	dev_priv->backlight.present = true;
+
 	return 0;
 }
 
@@ -839,6 +842,7 @@ void intel_panel_destroy_backlight(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	if (dev_priv->backlight.device) {
+		dev_priv->backlight.present = false;
 		backlight_device_unregister(dev_priv->backlight.device);
 		dev_priv->backlight.device = NULL;
 	}
-- 
1.8.5.3