From: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
You can't write it using the MCHBAR mirror, the write will just get
dropped.
This should make us BSpec-compliant, but there's no real bug I could
reproduce that is fixed by this patch.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_reg.h | 4 ++++
drivers/gpu/drm/i915/intel_display.c | 10 ++++++++--
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index bcee89b..ff60945 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1441,6 +1441,8 @@
* device 0 function 0's pci config register 0x44 or 0x48 and matches it in
* every way. It is not accessible from the CP register read instructions.
*
+ * Starting form Haswell, you can't write registers using the MCHBAR mirror,
+ * just read.
*/
#define MCHBAR_MIRROR_BASE 0x10000
@@ -4723,6 +4725,8 @@
#define GEN6_PCODE_READ_MIN_FREQ_TABLE 0x9
#define GEN6_PCODE_WRITE_RC6VIDS 0x4
#define GEN6_PCODE_READ_RC6VIDS 0x5
+#define GEN6_PCODE_READ_D_COMP 0x10
+#define GEN6_PCODE_WRITE_D_COMP 0x11
#define GEN6_ENCODE_RC6_VID(mv) (((mv) - 245) / 5)
#define GEN6_DECODE_RC6_VID(vids) (((vids) * 5) + 245)
#define GEN6_PCODE_DATA 0x138128
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 882da0e..3098465 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6019,7 +6019,10 @@ void hsw_disable_lcpll(struct drm_i915_private *dev_priv,
val = I915_READ(D_COMP);
val |= D_COMP_COMP_DISABLE;
- I915_WRITE(D_COMP, val);
+ mutex_lock(&dev_priv->rps.hw_lock);
+ if (sandybridge_pcode_write(dev_priv, GEN6_PCODE_WRITE_D_COMP, val))
+ DRM_ERROR("Failed to disable D_COMP\n");
+ mutex_unlock(&dev_priv->rps.hw_lock);
POSTING_READ(D_COMP);
ndelay(100);
@@ -6061,7 +6064,10 @@ void hsw_restore_lcpll(struct drm_i915_private *dev_priv)
val = I915_READ(D_COMP);
val |= D_COMP_COMP_FORCE;
val &= ~D_COMP_COMP_DISABLE;
- I915_WRITE(D_COMP, val);
+ mutex_lock(&dev_priv->rps.hw_lock);
+ if (sandybridge_pcode_write(dev_priv, GEN6_PCODE_WRITE_D_COMP, val))
+ DRM_ERROR("Failed to enable D_COMP\n");
+ mutex_unlock(&dev_priv->rps.hw_lock);
POSTING_READ(D_COMP);
val = I915_READ(LCPLL_CTL);
--
1.8.1.4
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