[Bug 73530] Asus U38N: Black screen with Radeon driver in Linux

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=73530

--- Comment #65 from Alex Deucher <agd5f at yahoo.com> ---
(In reply to Christian Aßfalg from comment #63)
> I think / guess that I am having the same issues. I've got the same laptop,
> running Arch Linux. Mostly, I've been using the proprietary catalyst driver,
> since I never got the free driver working. The proprietary is working fine.
> 
> What is the issue here? You've been playing with timings for the physical
> link to the internal panel? Is it so frickly? What would you need to fix the
> issue? How can I help?

In reply to Christian Aßfalg from comment #63)
> I think / guess that I am having the same issues. I've got the same laptop,
> running Arch Linux. Mostly, I've been using the proprietary catalyst driver,
> since I never got the free driver working. The proprietary is working fine.
> 
> What is the issue here? You've been playing with timings for the physical
> link to the internal panel? Is it so frickly? What would you need to fix the
> issue? How can I help?

I suggested that it might be a timing issue, and as per comment 54.  However,
link training is successful so that monitor accepts the parameters that the
driver proposed, it just sometimes chooses not to light up.  I would suggest
trying to tweak the link training timing as per comment 54, try disabling ss as
per comment 6, and finally, try making some slight changes to the modeset
sequence as per the attached patch.  The patch adds a delay before enabling the
video stream and additionally calls the enable video stream code again in case
the monitor didn't quite get the signal the first time.  E.g.,

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c
b/drivers/gpu/drm/radeon/atombios_encoders.c
index a7f2ddf..256ed7d 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -1687,8 +1687,12 @@ radeon_atom_encoder_dpms_dig(struct drm_encoder
*encoder, int mode)
                if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(encoder)) &&
connector) {
                        /* DP_SET_POWER_D0 is set in radeon_dp_link_train */
                        radeon_dp_link_train(encoder, connector);
-                       if (ASIC_IS_DCE4(rdev))
+                       if (ASIC_IS_DCE4(rdev)) {
+                               udelay(50);
                                atombios_dig_encoder_setup(encoder,
ATOM_ENCODER_CMD_DP_VIDEO_ON, 0);
+                               udelay(50);
+                               atombios_dig_encoder_setup(encoder,
ATOM_ENCODER_CMD_DP_VIDEO_ON, 0);
+                       }
                }
                if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT))
                        atombios_dig_transmitter_setup(encoder,

Or move the backlight enable before the link training:
diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c
b/drivers/gpu/drm/radeon/atombios_encoders.c
index a7f2ddf..3bfbfa4 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -1682,6 +1682,9 @@ radeon_atom_encoder_dpms_dig(struct drm_encoder *encoder,
int mode)
                                radeon_dig_connector->edp_on = true;
                        }
                }
+               if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT))
+                       atombios_dig_transmitter_setup(encoder,
+                                                     
ATOM_TRANSMITTER_ACTION_LCD_BLON, 0, 0);
                /* enable the transmitter */
                atombios_dig_transmitter_setup(encoder,
ATOM_TRANSMITTER_ACTION_ENABLE, 0, 0);
                if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(encoder)) &&
connector) {
@@ -1690,9 +1693,6 @@ radeon_atom_encoder_dpms_dig(struct drm_encoder *encoder,
int mode)
                        if (ASIC_IS_DCE4(rdev))
                                atombios_dig_encoder_setup(encoder,
ATOM_ENCODER_CMD_DP_VIDEO_ON, 0);
                }
-               if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT))
-                       atombios_dig_transmitter_setup(encoder,
-                                                     
ATOM_TRANSMITTER_ACTION_LCD_BLON, 0, 0);
                if (ext_encoder)
                        atombios_external_encoder_setup(encoder, ext_encoder,
ATOM_ENABLE);
                break;

Or drop the backlight control altogether to see if that helps:
diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c
b/drivers/gpu/drm/radeon/atombios_encoders.c
index a7f2ddf..9713078 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -1690,9 +1690,6 @@ radeon_atom_encoder_dpms_dig(struct drm_encoder *encoder,
int mode)
                        if (ASIC_IS_DCE4(rdev))
                                atombios_dig_encoder_setup(encoder,
ATOM_ENCODER_CMD_DP_VIDEO_ON, 0);
                }
-               if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT))
-                       atombios_dig_transmitter_setup(encoder,
-                                                     
ATOM_TRANSMITTER_ACTION_LCD_BLON, 0, 0);
                if (ext_encoder)
                        atombios_external_encoder_setup(encoder, ext_encoder,
ATOM_ENABLE);
                break;
@@ -1705,10 +1702,6 @@ radeon_atom_encoder_dpms_dig(struct drm_encoder
*encoder, int mode)
                }
                if (ext_encoder)
                        atombios_external_encoder_setup(encoder, ext_encoder,
ATOM_DISABLE);
-               if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT))
-                       atombios_dig_transmitter_setup(encoder,
-                                                     
ATOM_TRANSMITTER_ACTION_LCD_BLOFF, 0, 0);
-
                if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(encoder)) &&
                    connector && !travis_quirk)
                        radeon_dp_set_rx_power_state(connector,
DP_SET_POWER_D3);

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