[PATCH 02/16] drm/i915: Disable trickle feed for gen2/3

ville.syrjala
2014-08-14T22:22:18Z

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

My 830 is unhappy with trickle feed enabled. The symptom is that
the image on the screen shifts a bit to right occasionally.

The BIOS initially disables trickle feed, but it gets reset during
suspend, so we need to re-disable it ourselves. Juse disable it
always.

Also disable it for all other gen2/3 platforms since we disable it
for all more recent platforms as well (until HSW that is). At least
my 855 doesn't seem to mind us doing this. I don't have gen3
hardware to test that.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/i915_reg.h | 4 ++++
drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++++
2 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 203062e..b5fdffc 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1272,6 +1272,10 @@ enum punit_power_well {
#define INSTPM_TLB_INVALIDATE (1<<9)
#define INSTPM_SYNC_FLUSH (1<<5)
#define ACTHD 0x020c8
+#define MEM_MODE 0x020cc
+#define MEM_DISPLAY_B_TRICKLE_FEED_DISABLE (1<<3) /* 830 only */
+#define MEM_DISPLAY_A_TRICKLE_FEED_DISABLE (1<<2) /* 830/845 only */
+#define MEM_DISPLAY_TRICKLE_FEED_DISABLE (1<<2) /* 85x only */
#define FW_BLC 0x020d8
#define FW_BLC2 0x020dc
#define FW_BLC_SELF 0x020e0 /* 915+ only */
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index f696b7f..2865948 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6020,6 +6020,9 @@ static void gen3_init_clock_gating(struct drm_device *dev)

/* On GEN3 we really need to make sure the ARB C3 LP bit is set */
I915_WRITE(MI_ARB_STATE, _MASKED_BIT_ENABLE(MI_ARB_C3_LP_WRITE_ENABLE));
+
+ I915_WRITE(MI_ARB_STATE,
+ _MASKED_BIT_ENABLE(MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE));
}

static void i85x_init_clock_gating(struct drm_device *dev)
@@ -6031,6 +6034,9 @@ static void i85x_init_clock_gating(struct drm_device *dev)
/* interrupts should cause a wake up from C3 */
I915_WRITE(MI_STATE, _MASKED_BIT_ENABLE(MI_AGPBUSY_INT_EN) |
_MASKED_BIT_DISABLE(MI_AGPBUSY_830_MODE));
+
+ I915_WRITE(MEM_MODE,
+ _MASKED_BIT_ENABLE(MEM_DISPLAY_TRICKLE_FEED_DISABLE));
}

static void i830_init_clock_gating(struct drm_device *dev)
@@ -6038,6 +6044,10 @@ static void i830_init_clock_gating(struct drm_device *dev)
struct drm_i915_private *dev_priv = dev->dev_private;

I915_WRITE(DSPCLK_GATE_D, OVRUNIT_CLOCK_GATE_DISABLE);
+
+ I915_WRITE(MEM_MODE,
+ _MASKED_BIT_ENABLE(MEM_DISPLAY_A_TRICKLE_FEED_DISABLE) |
+ _MASKED_BIT_ENABLE(MEM_DISPLAY_B_TRICKLE_FEED_DISABLE));
}

void intel_init_clock_gating(struct drm_device *dev)
--
1.8.5.5