drm/radeon/kms/combios: verify dac_adj values are valid

Some vbios dac_adj tables are all zeros.  Check for that
case and use the default table if so.

Should fix fdo bug 27478.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_combios.c b/drivers/gpu/drm/radeon/radeon_combios.c
index 2becdeda68a..37db8adb274 100644
--- a/drivers/gpu/drm/radeon/radeon_combios.c
+++ b/drivers/gpu/drm/radeon/radeon_combios.c
@@ -760,7 +760,9 @@ struct radeon_encoder_primary_dac *radeon_combios_get_primary_dac_info(struct
                         dac = RBIOS8(dac_info + 0x3) & 0xf;
                         p_dac->ps2_pdac_adj = (bg << 8) | (dac);
                 }
-                found = 1;
+                /* if the values are all zeros, use the table */
+                if (p_dac->ps2_pdac_adj)
+                        found = 1;
         }
 
         if (!found) /* fallback to defaults */
@@ -895,7 +897,9 @@ struct radeon_encoder_tv_dac *radeon_combios_get_tv_dac_info(struct
                         bg = RBIOS8(dac_info + 0x10) & 0xf;
                         dac = RBIOS8(dac_info + 0x11) & 0xf;
                         tv_dac->ntsc_tvdac_adj = (bg << 16) | (dac << 20);
-                        found = 1;
+                        /* if the values are all zeros, use the table */
+                        if (tv_dac->ps2_tvdac_adj)
+                                found = 1;
                 } else if (rev > 1) {
                         bg = RBIOS8(dac_info + 0xc) & 0xf;
                         dac = (RBIOS8(dac_info + 0xc) >> 4) & 0xf;
@@ -908,7 +912,9 @@ struct radeon_encoder_tv_dac *radeon_combios_get_tv_dac_info(struct
                         bg = RBIOS8(dac_info + 0xe) & 0xf;
                         dac = (RBIOS8(dac_info + 0xe) >> 4) & 0xf;
                         tv_dac->ntsc_tvdac_adj = (bg << 16) | (dac << 20);
-                        found = 1;
+                        /* if the values are all zeros, use the table */
+                        if (tv_dac->ps2_tvdac_adj)
+                                found = 1;
                 }
                 tv_dac->tv_std = radeon_combios_get_tv_info(rdev);
         }
@@ -925,7 +931,9 @@ struct radeon_encoder_tv_dac *radeon_combios_get_tv_dac_info(struct
                                     (bg << 16) | (dac << 20);
                                 tv_dac->pal_tvdac_adj = tv_dac->ps2_tvdac_adj;
                                 tv_dac->ntsc_tvdac_adj = tv_dac->ps2_tvdac_adj;
-                                found = 1;
+                                /* if the values are all zeros, use the table */
+                                if (tv_dac->ps2_tvdac_adj)
+                                        found = 1;
                         } else {
                                 bg = RBIOS8(dac_info + 0x4) & 0xf;
                                 dac = RBIOS8(dac_info + 0x5) & 0xf;
@@ -933,7 +941,9 @@ struct radeon_encoder_tv_dac *radeon_combios_get_tv_dac_info(struct
                                     (bg << 16) | (dac << 20);
                                 tv_dac->pal_tvdac_adj = tv_dac->ps2_tvdac_adj;
                                 tv_dac->ntsc_tvdac_adj = tv_dac->ps2_tvdac_adj;
-                                found = 1;
+                                /* if the values are all zeros, use the table */
+                                if (tv_dac->ps2_tvdac_adj)
+                                        found = 1;
                         }
                 } else {
                         DRM_INFO("No TV DAC info found in BIOS\n");