radeon + DVI->mDP converter + mDP display blank screen issue since 3.0

Hi!

Since Linux 3.0, a system with a Radeon HD 5450 (1002:68f9) connected to a 27" Apple LED cinema display via an Atlona AT-DP400 Dual Link DVI to Mini DisplayPort converter has started to stop giving screen output on switching from text mode to graphical framebuffer during system startup.

I finally had some time to look at this, and it seems to have stopped working after this commit:

       commit df271bec805b42527d864777ed035fcbb42e76c0
       Author: Alex Deucher <[email protected]>
       Date:   Fri May 20 04:34:15 2011 -0400

           drm/radeon/kms: properly handle bpc >8 in atom command tables

Signed-off-by Alex Deucher <[email protected]>

Signed-off-by Dave Airlie <[email protected]>

...and with the patch below (i.e. reverting part of the commit above) applied to 3.3 I get screen output again.

Even though the monitor seems to have an 8 bit panel, it reports 10 bits per channel in its EDID:

       [...]
       Manufacturer: APP Model 9226 Serial Number 41959462 Made week 38 of 2010
       EDID version: 1.4
       Digital display
       10 bits per primary color channel DisplayPort interface
       Maximum image size: 60 cm x 34 cm
       [...]

The (active, dual link) DVI->mDP converter spec sheet says it supports 24 bit color, and I'm guessing that it can't deal with 30.  Is the converter at fault here for passing through the EDID unchanged?

Also, what would be the right way to handle this, a kernel command line or module option to limit color depth or something like that? ("Buy a video card with DP output." is a valid answer, I suppose.)

I have no clue at all about graphics, and I have no idea whatsoever what I'm doing here, but I just wanted to post this somewhere for Google to find in case someone else runs into this!

thanks,
Lennert

drivers/gpu/drm/radeon/atombios_crtc.c +0 -5

index 742f17f..77a6a04 100644
@@ -513,11 +513,9 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
        struct radeon_device *rdev = dev->dev_private;
        struct drm_encoder *encoder = NULL;
        struct radeon_encoder *radeon_encoder = NULL;
-       struct drm_connector *connector = NULL;
        u32 adjusted_clock = mode->clock;
        int encoder_mode = 0;
        u32 dp_clock = mode->clock;
-       int bpc = 8;
        bool is_duallink = false;
 
        /* reset the pll flags */

@@ -549,13 +547,11 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
        list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
                if (encoder->crtc == crtc) {
                        radeon_encoder = to_radeon_encoder(encoder);
-                       connector = radeon_get_connector_for_encoder(encoder);
-                       if (connector && connector->display_info.bpc)
-                               bpc = connector->display_info.bpc;
                        encoder_mode = atombios_get_encoder_mode(encoder);
                        is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);

                       if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) || (radeon_encoder_get_dp_bridge_encoder_id(encoder) != ENCODER_OBJECT_ID_NONE)) {
+                               struct drm_connector *connector = radeon_get_connector_for_encoder(encoder); if (connector) {
                                       struct radeon_connector *radeon_connector = to_radeon_connector(connector); struct radeon_connector_atom_dig *dig_connector =

drivers/gpu/drm/radeon/atombios_crtc.c +0 -0

@@ -645,7 +641,7 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
                                        if (encoder_mode == ATOM_ENCODER_MODE_HDMI)
                                                /* deep color support */

                                               args.v3.sInput.usPixelClock =
-                                                       cpu_to_le16((mode->clock * bpc / 8) / 10);
+                                                       cpu_to_le16(mode->clock / 10); if (dig->coherent_mode) args.v3.sInput.ucDispPllConfig |= DISPPLL_CONFIG_COHERENT_MODE;

drivers/gpu/drm/radeon/atombios_crtc.c +0 -1

@@ -753,7 +749,6 @@ static void atombios_crtc_program_pll(struct drm_crtc *crtc,
                                      u32 fb_div,
                                      u32 frac_fb_div,
                                      u32 post_div,
-                                     int bpc,
                                      bool ss_enabled,
                                      struct radeon_atom_ss *ss)
  {

@@ -817,15 +812,6 @@ static void atombios_crtc_program_pll(struct drm_crtc *crtc,

                       args.v5.ucMiscInfo = 0; /* HDMI depth, etc. */ if (ss_enabled && (ss->type & ATOM_EXTERNAL_SS_MASK)) args.v5.ucMiscInfo |= PIXEL_CLOCK_V5_MISC_REF_DIV_SRC;
-                       switch (bpc) {
-                       case 8:
-                       default:
-                               args.v5.ucMiscInfo |= PIXEL_CLOCK_V5_MISC_HDMI_24BPP;
-                               break;
-                       case 10:
-                               args.v5.ucMiscInfo |= PIXEL_CLOCK_V5_MISC_HDMI_30BPP;
-                               break;
-                       }
                       args.v5.ucTransmitterID = encoder_id; args.v5.ucEncoderMode = encoder_mode; args.v5.ucPpll = pll_id;

drivers/gpu/drm/radeon/atombios_crtc.c +0 -0

@@ -839,21 +825,6 @@ static void atombios_crtc_program_pll(struct drm_crtc *crtc,

                       args.v6.ucMiscInfo = 0; /* HDMI depth, etc. */ if (ss_enabled && (ss->type & ATOM_EXTERNAL_SS_MASK)) args.v6.ucMiscInfo |= PIXEL_CLOCK_V6_MISC_REF_DIV_SRC;
-                       switch (bpc) {
-                       case 8:
-                       default:
-                               args.v6.ucMiscInfo |= PIXEL_CLOCK_V6_MISC_HDMI_24BPP;
-                               break;
-                       case 10:
-                               args.v6.ucMiscInfo |= PIXEL_CLOCK_V6_MISC_HDMI_30BPP;
-                               break;
-                       case 12:
-                               args.v6.ucMiscInfo |= PIXEL_CLOCK_V6_MISC_HDMI_36BPP;
-                               break;
-                       case 16:
-                               args.v6.ucMiscInfo |= PIXEL_CLOCK_V6_MISC_HDMI_48BPP;
-                               break;
-                       }
                       args.v6.ucTransmitterID = encoder_id; args.v6.ucEncoderMode = encoder_mode; args.v6.ucPpll = pll_id;

drivers/gpu/drm/radeon/atombios_crtc.c +0 -1

@@ -885,7 +856,6 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
        int encoder_mode = 0;
        struct radeon_atom_ss ss;
        bool ss_enabled = false;
-       int bpc = 8;
 
        list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
                if (encoder->crtc == crtc) {

@@ -922,7 +892,6 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode

               struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
               int dp_clock;
-               bpc = connector->display_info.bpc;

               switch (encoder_mode) {
               case ATOM_ENCODER_MODE_DP_MST:

drivers/gpu/drm/radeon/atombios_crtc.c +1 -1

@@ -995,7 +964,7 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
 
        atombios_crtc_program_pll(crtc, radeon_crtc->crtc_id, radeon_crtc->pll_id,
                                  encoder_mode, radeon_encoder->encoder_id, mode->clock,
-                                 ref_div, fb_div, frac_fb_div, post_div, bpc, ss_enabled, &ss);
+                                 ref_div, fb_div, frac_fb_div, post_div, ss_enabled, &ss);
 
        if (ss_enabled) {
                /* calculate ss amount and step size */

@@ -1587,7 +1556,7 @@ static void atombios_crtc_disable(struct drm_crtc *crtc)

       case ATOM_PPLL2:
               /* disable the ppll */
               atombios_crtc_program_pll(crtc, radeon_crtc->crtc_id, radeon_crtc->pll_id,
-                                         0, 0, ATOM_DISABLE, 0, 0, 0, 0, 0, false, &ss);

+                                         0, 0, ATOM_DISABLE, 0, 0, 0, 0, false, &ss); break;
       default:
               break;
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Quoted 42 lines

Since Linux 3.0, a system with a Radeon HD 5450 (1002:68f9) connected to a 27" Apple LED cinema display via an Atlona AT-DP400 Dual Link DVI to Mini DisplayPort converter has started to stop giving screen output on switching from text mode to graphical framebuffer during system startup.

I finally had some time to look at this, and it seems to have stopped working after this commit:

       commit df271bec805b42527d864777ed035fcbb42e76c0
       Author: Alex Deucher <[email protected]>
       Date:   Fri May 20 04:34:15 2011 -0400

           drm/radeon/kms: properly handle bpc >8 in atom command tables

Signed-off-by Alex Deucher <[email protected]>

Signed-off-by Dave Airlie <[email protected]>

...and with the patch below (i.e. reverting part of the commit above) applied to 3.3 I get screen output again.

Even though the monitor seems to have an 8 bit panel, it reports 10 bits per channel in its EDID:

       [...]
       Manufacturer: APP Model 9226 Serial Number 41959462 Made week 38 of 2010
       EDID version: 1.4
       Digital display
       10 bits per primary color channel DisplayPort interface
       Maximum image size: 60 cm x 34 cm
       [...]

The (active, dual link) DVI->mDP converter spec sheet says it supports 24 bit color, and I'm guessing that it can't deal with 30.  Is the converter at fault here for passing through the EDID unchanged?

Also, what would be the right way to handle this, a kernel command line or module option to limit color depth or something like that? ("Buy a video card with DP output." is a valid answer, I suppose.)

Quoted 3 lines

I have no clue at all about graphics, and I have no idea whatsoever what I'm doing here, but I just wanted to post this somewhere for Google to find in case someone else runs into this!

I've inquired with out display team on how to best handle this. In the meantime, it's probably best to just default to 8 bpc. Does the attached patch fix your issue?

From 22ca454eb749968f266d6788a5f4778acc08cc66 Mon Sep 17 00:00:00 2001
From: Alex Deucher <[email protected]>
Date: Fri, 23 Mar 2012 10:54:45 -0400
Subject: [PATCH] drm/radeon/kms/atom: force bpc to 8 for now

Using the bpc (bits per color) specified by the monitor can cause problems in some cases. Until we get a better handle on how to deal with those cases, just use a bpc of 8.

Reported-by Lennert Buytenhek <[email protected]>

Signed-off-by Alex Deucher <[email protected]>

Cc [email protected]

---
 drivers/gpu/drm/radeon/atombios_crtc.c     |    8 +++++---
 drivers/gpu/drm/radeon/atombios_dp.c       |    3 +++
 drivers/gpu/drm/radeon/atombios_encoders.c |    4 ++--
 3 files changed, 10 insertions(+), 5 deletions(-)

drivers/gpu/drm/radeon/atombios_crtc.c +5 -3

index 083b3ea..b5ff1f7 100644
@@ -588,8 +588,8 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
 		if (encoder->crtc == crtc) {
 			radeon_encoder = to_radeon_encoder(encoder);
 			connector = radeon_get_connector_for_encoder(encoder);
-			if (connector && connector->display_info.bpc)
-				bpc = connector->display_info.bpc;
+			/* if (connector && connector->display_info.bpc)
+				bpc = connector->display_info.bpc; */
 			encoder_mode = atombios_get_encoder_mode(encoder);
 			is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);
 			if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) ||

@@ -965,7 +965,9 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
 		struct radeon_connector_atom_dig *dig_connector =
 			radeon_connector->con_priv;
 		int dp_clock;
-		bpc = connector->display_info.bpc;
+
+		/* if (connector->display_info.bpc)
+			bpc = connector->display_info.bpc; */
 
 		switch (encoder_mode) {
 		case ATOM_ENCODER_MODE_DP_MST:

drivers/gpu/drm/radeon/atombios_dp.c +3 -0

index 6c62be2..c57d856 100644
@@ -405,10 +405,13 @@ static void dp_get_adjust_train(u8 link_status[DP_LINK_STATUS_SIZE],
 /* get bpc from the EDID */
 static int convert_bpc_to_bpp(int bpc)
 {
+#if 0
 	if (bpc == 0)
 		return 24;
 	else
 		return bpc * 3;
+#endif
+	return 24;
 }
 
 /* get the max pix clock supported by the link rate and lane num */

drivers/gpu/drm/radeon/atombios_encoders.c +2 -2

index 468b874..e607c4d 100644
@@ -541,7 +541,7 @@ atombios_dig_encoder_setup(struct drm_encoder *encoder, int action, int panel_mo
 		dp_clock = dig_connector->dp_clock;
 		dp_lane_count = dig_connector->dp_lane_count;
 		hpd_id = radeon_connector->hpd.hpd;
-		bpc = connector->display_info.bpc;
+		/* bpc = connector->display_info.bpc; */
 	}
 
 	/* no dig encoder assigned */

@@ -1159,7 +1159,7 @@ atombios_external_encoder_setup(struct drm_encoder *encoder,
 		dp_lane_count = dig_connector->dp_lane_count;
 		connector_object_id =
 			(radeon_connector->connector_object_id & OBJECT_ID_MASK) >> OBJECT_ID_SHIFT;
-		bpc = connector->display_info.bpc;
+		/* bpc = connector->display_info.bpc; */
 	}
 
 	memset(&args, 0, sizeof(args));

Signature · 1 line

1.7.7.5

Quoted 46 lines · Alex Deucher

Quoted 45 lines

Since Linux 3.0, a system with a Radeon HD 5450 (1002:68f9) connected to a 27" Apple LED cinema display via an Atlona AT-DP400 Dual Link DVI to Mini DisplayPort converter has started to stop giving screen output on switching from text mode to graphical framebuffer during system startup.

I finally had some time to look at this, and it seems to have stopped working after this commit:

       commit df271bec805b42527d864777ed035fcbb42e76c0
       Author: Alex Deucher <[email protected]>
       Date:   Fri May 20 04:34:15 2011 -0400

           drm/radeon/kms: properly handle bpc >8 in atom command tables

Signed-off-by Alex Deucher <[email protected]>

Signed-off-by Dave Airlie <[email protected]>

...and with the patch below (i.e. reverting part of the commit above) applied to 3.3 I get screen output again.

Even though the monitor seems to have an 8 bit panel, it reports 10 bits per channel in its EDID:

       [...]
       Manufacturer: APP Model 9226 Serial Number 41959462 Made week 38 of 2010
       EDID version: 1.4
       Digital display
       10 bits per primary color channel DisplayPort interface
       Maximum image size: 60 cm x 34 cm
       [...]

The (active, dual link) DVI->mDP converter spec sheet says it supports 24 bit color, and I'm guessing that it can't deal with 30.  Is the converter at fault here for passing through the EDID unchanged?

Also, what would be the right way to handle this, a kernel command line or module option to limit color depth or something like that? ("Buy a video card with DP output." is a valid answer, I suppose.)

I have no clue at all about graphics, and I have no idea whatsoever what I'm doing here, but I just wanted to post this somewhere for Google to find in case someone else runs into this!

Quoted 3 lines

I've inquired with out display team on how to best handle this.  In the meantime, it's probably best to just default to 8 bpc.  Does the attached patch fix your issue?

I've been using the patch below in a custom Fedora 17 kernel RPM, and that seems to fix the issue.  Your patch seems to be a superset of this patch, so logically, your patch should do the trick as well. :)

thanks,
Lennert

diff -up linux-3.3.0-1.fc17.x86_64/drivers/gpu/drm/radeon/atombios_crtc.c.orig linux-3.3.0-1.fc17.x86_64/drivers/gpu/drm/radeon/atombios_crtc.c

drivers/gpu/drm/radeon/atombios_crtc.c    2012-03-22 14:55:39.740794113 +0100 renamed from drivers/gpu/drm/radeon/atombios_crtc.c.orig       2012-03-22 14:52:20.538854547 +0100 +0 -2

@@ -550,8 +550,6 @@ static u32 atombios_adjust_pll(struct dr
                if (encoder->crtc == crtc) {
                        radeon_encoder = to_radeon_encoder(encoder);
                        connector = radeon_get_connector_for_encoder(encoder);
-                       if (connector && connector->display_info.bpc)
-                               bpc = connector->display_info.bpc;
                        encoder_mode = atombios_get_encoder_mode(encoder);
                        is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);

                       if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) ||

drivers/gpu/drm/radeon/atombios_crtc.c    2012-03-22 14:55:39.740794113 +0100 renamed from drivers/gpu/drm/radeon/atombios_crtc.c.orig       2012-03-22 14:52:20.538854547 +0100 +0 -0

@@ -922,7 +920,6 @@ static void atombios_crtc_set_pll(struct

               struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
               int dp_clock;
-               bpc = connector->display_info.bpc;

               switch (encoder_mode) {
               case ATOM_ENCODER_MODE_DP_MST:

Quoted 83 lines

From 22ca454eb749968f266d6788a5f4778acc08cc66 Mon Sep 17 00:00:00 2001
From: Alex Deucher <[email protected]>
Date: Fri, 23 Mar 2012 10:54:45 -0400
Subject: [PATCH] drm/radeon/kms/atom: force bpc to 8 for now

Using the bpc (bits per color) specified by the monitor can cause problems in some cases.  Until we get a better handle on how to deal with those cases, just use a bpc of 8.

Reported-by Lennert Buytenhek <[email protected]>

Signed-off-by Alex Deucher <[email protected]>

Cc [email protected]

---
 drivers/gpu/drm/radeon/atombios_crtc.c     |    8 +++++--- drivers/gpu/drm/radeon/atombios_dp.c       |    3 +++ drivers/gpu/drm/radeon/atombios_encoders.c |    4 ++--

 3 files changed, 10 insertions(+), 5 deletions(-)

drivers/gpu/drm/radeon/atombios_crtc.c +2 -2

index 083b3ea..b5ff1f7 100644
@@ -588,8 +588,8 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
               if (encoder->crtc == crtc) {
                       radeon_encoder = to_radeon_encoder(encoder);
                       connector = radeon_get_connector_for_encoder(encoder);
-                     if (connector && connector->display_info.bpc)
-                             bpc = connector->display_info.bpc;
+                     /* if (connector && connector->display_info.bpc)
+                             bpc = connector->display_info.bpc; */
                       encoder_mode = atombios_get_encoder_mode(encoder);
                       is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);

                      if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) ||

drivers/gpu/drm/radeon/atombios_crtc.c +0 -0

@@ -965,7 +965,9 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode

              struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
              int dp_clock;
-             bpc = connector->display_info.bpc;
+
+             /* if (connector->display_info.bpc)
+                     bpc = connector->display_info.bpc; */

              switch (encoder_mode) {
              case ATOM_ENCODER_MODE_DP_MST:

drivers/gpu/drm/radeon/atombios_dp.c +1 -0

index 6c62be2..c57d856 100644
@@ -405,10 +405,13 @@ static void dp_get_adjust_train(u8 link_status[DP_LINK_STATUS_SIZE],
  /* get bpc from the EDID */
  static int convert_bpc_to_bpp(int bpc)
  {
+#if 0
       if (bpc == 0)
               return 24;

      else
              return bpc * 3;
+#endif
+     return 24;
 }

 /* get the max pix clock supported by the link rate and lane num */

drivers/gpu/drm/radeon/atombios_encoders.c +1 -1

index 468b874..e607c4d 100644
@@ -541,7 +541,7 @@ atombios_dig_encoder_setup(struct drm_encoder *encoder, int action, int panel_mo
               dp_clock = dig_connector->dp_clock;
               dp_lane_count = dig_connector->dp_lane_count;
               hpd_id = radeon_connector->hpd.hpd;
-             bpc = connector->display_info.bpc;
+             /* bpc = connector->display_info.bpc; */
       }
 
       /* no dig encoder assigned */

@@ -1159,7 +1159,7 @@ atombios_external_encoder_setup(struct drm_encoder *encoder,
               dp_lane_count = dig_connector->dp_lane_count;

              connector_object_id =
                      (radeon_connector->connector_object_id & OBJECT_ID_MASK) >> OBJECT_ID_SHIFT;
-             bpc = connector->display_info.bpc;
+             /* bpc = connector->display_info.bpc; */
      }

Quoted 4 lines

      memset(&args, 0, sizeof(args));
--
1.7.7.5

Quoted 52 lines · Lennert Buytenhek

Quoted 49 lines · Alex Deucher

Quoted 38 lines

Since Linux 3.0, a system with a Radeon HD 5450 (1002:68f9) connected to a 27" Apple LED cinema display via an Atlona AT-DP400 Dual Link DVI to Mini DisplayPort converter has started to stop giving screen output on switching from text mode to graphical framebuffer during system startup.

I finally had some time to look at this, and it seems to have stopped working after this commit:

       commit df271bec805b42527d864777ed035fcbb42e76c0
       Author: Alex Deucher <[email protected]>
       Date:   Fri May 20 04:34:15 2011 -0400

           drm/radeon/kms: properly handle bpc >8 in atom command tables

Signed-off-by Alex Deucher <[email protected]>

Signed-off-by Dave Airlie <[email protected]>

...and with the patch below (i.e. reverting part of the commit above) applied to 3.3 I get screen output again.

Even though the monitor seems to have an 8 bit panel, it reports 10 bits per channel in its EDID:

       [...]
       Manufacturer: APP Model 9226 Serial Number 41959462 Made week 38 of 2010
       EDID version: 1.4
       Digital display
       10 bits per primary color channel DisplayPort interface
       Maximum image size: 60 cm x 34 cm
       [...]

The (active, dual link) DVI->mDP converter spec sheet says it supports 24 bit color, and I'm guessing that it can't deal with 30.  Is the converter at fault here for passing through the EDID unchanged?

Quoted 7 lines

Also, what would be the right way to handle this, a kernel command line or module option to limit color depth or something like that? ("Buy a video card with DP output." is a valid answer, I suppose.)

I have no clue at all about graphics, and I have no idea whatsoever what I'm doing here, but I just wanted to post this somewhere for Google to find in case someone else runs into this!

I've inquired with out display team on how to best handle this.  In the meantime, it's probably best to just default to 8 bpc.  Does the attached patch fix your issue?

Quoted 3 lines

I've been using the patch below in a custom Fedora 17 kernel RPM, and that seems to fix the issue.  Your patch seems to be a superset of this patch, so logically, your patch should do the trick as well. :)

Can you try the attached patch on top of my previous one?

Alex

Quoted 112 lines

thanks,
Lennert

diff -up linux-3.3.0-1.fc17.x86_64/drivers/gpu/drm/radeon/atombios_crtc.c.orig linux-3.3.0-1.fc17.x86_64/drivers/gpu/drm/radeon/atombios_crtc.c

drivers/gpu/drm/radeon/atombios_crtc.c    2012-03-22 14:55:39.740794113 +0100 renamed from drivers/gpu/drm/radeon/atombios_crtc.c.orig       2012-03-22 14:52:20.538854547 +0100 +0 -2

@@ -550,8 +550,6 @@ static u32 atombios_adjust_pll(struct dr
                if (encoder->crtc == crtc) {
                        radeon_encoder = to_radeon_encoder(encoder);
                        connector = radeon_get_connector_for_encoder(encoder);
-                       if (connector && connector->display_info.bpc)
-                               bpc = connector->display_info.bpc;
                        encoder_mode = atombios_get_encoder_mode(encoder);
                        is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);

                       if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) ||

drivers/gpu/drm/radeon/atombios_crtc.c    2012-03-22 14:55:39.740794113 +0100 renamed from drivers/gpu/drm/radeon/atombios_crtc.c.orig       2012-03-22 14:52:20.538854547 +0100 +0 -0

@@ -922,7 +920,6 @@ static void atombios_crtc_set_pll(struct

               struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
               int dp_clock;
-               bpc = connector->display_info.bpc;

               switch (encoder_mode) {
               case ATOM_ENCODER_MODE_DP_MST:

Quoted 83 lines

From 22ca454eb749968f266d6788a5f4778acc08cc66 Mon Sep 17 00:00:00 2001
From: Alex Deucher <[email protected]>
Date: Fri, 23 Mar 2012 10:54:45 -0400
Subject: [PATCH] drm/radeon/kms/atom: force bpc to 8 for now

Using the bpc (bits per color) specified by the monitor can cause problems in some cases.  Until we get a better handle on how to deal with those cases, just use a bpc of 8.

Reported-by Lennert Buytenhek <[email protected]>

Signed-off-by Alex Deucher <[email protected]>

Cc [email protected]

---
 drivers/gpu/drm/radeon/atombios_crtc.c     |    8 +++++--- drivers/gpu/drm/radeon/atombios_dp.c       |    3 +++ drivers/gpu/drm/radeon/atombios_encoders.c |    4 ++--

 3 files changed, 10 insertions(+), 5 deletions(-)

drivers/gpu/drm/radeon/atombios_crtc.c +2 -2

index 083b3ea..b5ff1f7 100644
@@ -588,8 +588,8 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
               if (encoder->crtc == crtc) {
                       radeon_encoder = to_radeon_encoder(encoder);
                       connector = radeon_get_connector_for_encoder(encoder);
-                     if (connector && connector->display_info.bpc)
-                             bpc = connector->display_info.bpc;
+                     /* if (connector && connector->display_info.bpc)
+                             bpc = connector->display_info.bpc; */
                       encoder_mode = atombios_get_encoder_mode(encoder);
                       is_duallink = radeon_dig_monitor_is_duallink(encoder, mode->clock);

                      if ((radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT | ATOM_DEVICE_DFP_SUPPORT)) ||

drivers/gpu/drm/radeon/atombios_crtc.c +0 -0

@@ -965,7 +965,9 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode

              struct radeon_connector_atom_dig *dig_connector = radeon_connector->con_priv;
              int dp_clock;
-             bpc = connector->display_info.bpc;
+
+             /* if (connector->display_info.bpc)
+                     bpc = connector->display_info.bpc; */

              switch (encoder_mode) {
              case ATOM_ENCODER_MODE_DP_MST:

drivers/gpu/drm/radeon/atombios_dp.c +1 -0

index 6c62be2..c57d856 100644
@@ -405,10 +405,13 @@ static void dp_get_adjust_train(u8 link_status[DP_LINK_STATUS_SIZE],
  /* get bpc from the EDID */
  static int convert_bpc_to_bpp(int bpc)
  {
+#if 0
       if (bpc == 0)
               return 24;

      else
              return bpc * 3;
+#endif
+     return 24;
 }

 /* get the max pix clock supported by the link rate and lane num */

drivers/gpu/drm/radeon/atombios_encoders.c +1 -1

index 468b874..e607c4d 100644
@@ -541,7 +541,7 @@ atombios_dig_encoder_setup(struct drm_encoder *encoder, int action, int panel_mo
               dp_clock = dig_connector->dp_clock;
               dp_lane_count = dig_connector->dp_lane_count;
               hpd_id = radeon_connector->hpd.hpd;
-             bpc = connector->display_info.bpc;
+             /* bpc = connector->display_info.bpc; */
       }
 
       /* no dig encoder assigned */

@@ -1159,7 +1159,7 @@ atombios_external_encoder_setup(struct drm_encoder *encoder,
               dp_lane_count = dig_connector->dp_lane_count;

              connector_object_id =
                      (radeon_connector->connector_object_id & OBJECT_ID_MASK) >> OBJECT_ID_SHIFT;
-             bpc = connector->display_info.bpc;
+             /* bpc = connector->display_info.bpc; */
      }

Quoted 4 lines

Quoted 4 lines

      memset(&args, 0, sizeof(args));
--
1.7.7.5

Quoted 50 lines

Quoted 50 lines

Quoted 49 lines

Quoted 38 lines

Since Linux 3.0, a system with a Radeon HD 5450 (1002:68f9) connected to a 27" Apple LED cinema display via an Atlona AT-DP400 Dual Link DVI to Mini DisplayPort converter has started to stop giving screen output on switching from text mode to graphical framebuffer during system startup.

I finally had some time to look at this, and it seems to have stopped working after this commit:

       commit df271bec805b42527d864777ed035fcbb42e76c0
       Author: Alex Deucher <[email protected]>
       Date:   Fri May 20 04:34:15 2011 -0400

           drm/radeon/kms: properly handle bpc >8 in atom command tables

Signed-off-by Alex Deucher <[email protected]>

Signed-off-by Dave Airlie <[email protected]>

...and with the patch below (i.e. reverting part of the commit above) applied to 3.3 I get screen output again.

Even though the monitor seems to have an 8 bit panel, it reports 10 bits per channel in its EDID:

       [...]
       Manufacturer: APP Model 9226 Serial Number 41959462 Made week 38 of 2010
       EDID version: 1.4
       Digital display
       10 bits per primary color channel DisplayPort interface
       Maximum image size: 60 cm x 34 cm
       [...]

The (active, dual link) DVI->mDP converter spec sheet says it supports 24 bit color, and I'm guessing that it can't deal with 30.  Is the converter at fault here for passing through the EDID unchanged?

Quoted 7 lines

Also, what would be the right way to handle this, a kernel command line or module option to limit color depth or something like that? ("Buy a video card with DP output." is a valid answer, I suppose.)

I have no clue at all about graphics, and I have no idea whatsoever what I'm doing here, but I just wanted to post this somewhere for Google to find in case someone else runs into this!

I've inquired with out display team on how to best handle this.  In the meantime, it's probably best to just default to 8 bpc.  Does the attached patch fix your issue?

Quoted 5 lines

Quoted 3 lines

I've been using the patch below in a custom Fedora 17 kernel RPM, and that seems to fix the issue.  Your patch seems to be a superset of this patch, so logically, your patch should do the trick as well. :)

Can you try the attached patch on top of my previous one?

Scratch that. Try this one instead.