drm/i915/tv: Preserve reserved DAC bits during mode-setting

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

2 files changed, 2 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d094e9129223..e240de9eed57 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1481,6 +1481,7 @@
 # define TV_TEST_MODE_MASK              (7 << 0)
 
 #define TV_DAC                  0x68004
+# define TV_DAC_SAVE            0x00ffff00
 /**
  * Reports that DAC state change logic has reported change (RO).
  *
diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index c671f60ce80b..fc5c6f2008fb 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1196,7 +1196,7 @@ intel_tv_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
                 I915_WRITE(TV_V_LUMA_0 + (i<<2), tv_mode->filter_table[j++]);
         for (i = 0; i < 43; i++)
                 I915_WRITE(TV_V_CHROMA_0 + (i<<2), tv_mode->filter_table[j++]);
-        I915_WRITE(TV_DAC, 0);
+        I915_WRITE(TV_DAC, I915_READ(TV_DAC) & TV_DAC_SAVE);
         I915_WRITE(TV_CTL, tv_ctl);
 }