Re: No backlight since linux-4.2.4 - drivers/gpu/drm/radeon/atombios_encoders.c

["Michel Dänzer" <michel@daenzer.net>]

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On 25.10.2015 04:25, Michael Burian wrote:
> hi,
> 
> after updating the kernel from linux-stable[0] v4.2.3 to v4.2.4 on my
> hp compaq nx9420 laptop (Debian Jessie, amd64), the backlight is turned off
> within the first couple of seconds during boot.
> 
> The situation persists (Xorg seems to be running fine, icons can be recognized
> by illuminating the screen with a flashlight) until reboot using an earlier
> kernel.
> 
> current mainline[1] as of now (4.3.0-rc6-00277-g01815536) is also affected
> 
> Workaround: use earlier kernel (v4.2.3) or (see below)
> 
> Hardware:
> 
> lspci | grep adeo
> 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV530/M56-P [Mobility Radeon X1600]
> 
> git bisect log
> # bad: [190bd21bba09ed476d9359d3e8be20e8d9dcd8a4] Linux 4.2.4
> # good: [fcba09f2b0bf27eeaa1d4d439edb649585f35040] Linux 4.2.3
> git bisect start 'v4.2.4' 'v4.2.3' 'drivers/gpu/'
> # good: [885838eef785ff810dac945be8132856f2113cf1] drm/amdgpu: make UVD handle checking more strict
> git bisect good 885838eef785ff810dac945be8132856f2113cf1
> # good: [230f6fd628c83fcb44ea364d69a9ad88826ef8c4] drm/i915/bios: handle MIPI Sequence Block v3+ gracefully
> git bisect good 230f6fd628c83fcb44ea364d69a9ad88826ef8c4
> # bad: [5a633828b4b2bef343826afcb0a70770c4911c55] drm/radeon: Restore LCD backlight level on resume (>= R5xx)
> git bisect bad 5a633828b4b2bef343826afcb0a70770c4911c55
> # good: [60a09aef456ef590762d47da9c25650e230e2f85] drm: Reject DRI1 hw lock ioctl functions for kms drivers
> git bisect good 60a09aef456ef590762d47da9c25650e230e2f85
> # first bad commit: [5a633828b4b2bef343826afcb0a70770c4911c55] drm/radeon: Restore LCD backlight level on resume (>= R5xx)
> 
> Workaround 2:
> 
> reverting this single commit 5a633828b4b2bef343826afcb0a70770c4911c55 fixes the problem in linux-stable[0]
> as well as mainline[1] 4.3.0-rc6-00277-g01815536

Please provide the dmesg output from running with the attached debugging
patch.


Alex, any other ideas what might go wrong?


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index 65adb9c..31be81e 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -77,9 +77,12 @@ atombios_get_backlight_level(struct radeon_encoder *radeon_encoder)
 	struct drm_device *dev = radeon_encoder->base.dev;
 	struct radeon_device *rdev = dev->dev_private;
 
-	if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
+	if (WARN_ON(!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU)))
 		return 0;
 
+	DRM_INFO("Backlight controlled by GPU, current level %u\n",
+		 radeon_atom_get_backlight_level_from_reg(rdev));
+
 	return radeon_atom_get_backlight_level_from_reg(rdev);
 }
 
@@ -93,7 +96,7 @@ atombios_set_backlight_level(struct radeon_encoder *radeon_encoder, u8 level)
 	DISPLAY_DEVICE_OUTPUT_CONTROL_PS_ALLOCATION args;
 	int index;
 
-	if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
+	if (WARN_ON(!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU)))
 		return;
 
 	if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT)) &&
@@ -105,6 +108,7 @@ atombios_set_backlight_level(struct radeon_encoder *radeon_encoder, u8 level)
 		switch (radeon_encoder->encoder_id) {
 		case ENCODER_OBJECT_ID_INTERNAL_LVDS:
 		case ENCODER_OBJECT_ID_INTERNAL_LVTM1:
+			DRM_INFO("Setting LVDS backlight level to %u\n", level);
 			index = GetIndexIntoMasterTable(COMMAND, LCD1OutputControl);
 			if (dig->backlight_level == 0) {
 				args.ucAction = ATOM_LCD_BLOFF;
@@ -120,6 +124,7 @@ atombios_set_backlight_level(struct radeon_encoder *radeon_encoder, u8 level)
 		case ENCODER_OBJECT_ID_INTERNAL_KLDSCP_LVTMA:
 		case ENCODER_OBJECT_ID_INTERNAL_UNIPHY1:
 		case ENCODER_OBJECT_ID_INTERNAL_UNIPHY2:
+			DRM_INFO("Setting UNIPHY backlight level to %u\n", level);
 			if (dig->backlight_level == 0)
 				atombios_dig_transmitter_setup(encoder, ATOM_TRANSMITTER_ACTION_LCD_BLOFF, 0, 0);
 			else {
@@ -199,7 +204,7 @@ void radeon_atom_backlight_init(struct radeon_encoder *radeon_encoder,
 	if (!rdev->is_atom_bios)
 		return;
 
-	if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
+	if (WARN_ON(!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU)))
 		return;
 
 	pdata = kmalloc(sizeof(struct radeon_backlight_privdata), GFP_KERNEL);

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