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>

diff --git a/drivers/gpu/drm/radeon/radeon_combios.c b/drivers/gpu/drm/radeon/radeon_combios.c
index 2becded..37db8ad 100644 (file)
--- 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");