While browsing BSpec I bumped into a note saying we need to tune these
values based on actual measurements done after initial enabling. I've
checked that it indeed improves things on BXT. I haven't checked this on
CHV, but here it is if someone wants to give it a go.
v2:
- Add note about the discrepancy wrt. to the spec in the formula
calculating the credit encodings. (Mika, Ville)
- Move the WA comment to the new function. (Ville)
CC: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
CC: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_reg.h | 6 ++++++
drivers/gpu/drm/i915/intel_pm.c | 47 +++++++++++++++++++++++++++--------------
2 files changed, 37 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0cb2e17..e25e78f 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6073,6 +6073,12 @@ enum skl_disp_power_wells {
#define VLV_B0_WA_L3SQCREG1_VALUE 0x00D30000
#define GEN8_L3SQCREG1 _MMIO(0xB100)
+/*
+ * Note that on CHV the following has an off-by-one error wrt. to BSpec.
+ * Using the formula in BSpec leads to a hang, while the formula here works
+ * fine and matches the formulas for all other platforms. A BSpec change
+ * request has been filed to clarify this.
+ */
#define L3_GENERAL_PRIO_CREDITS(x) (((x) >> 1) << 19)
#define L3_HIGH_PRIO_CREDITS(x) (((x) >> 1) << 14)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a9b7626..b217c44 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6669,11 +6669,38 @@ static void lpt_suspend_hw(struct drm_device *dev)
}
}
+static void gen8_set_l3sqc_credits(struct drm_i915_private *dev_priv,
+ int general_prio_credits,
+ int high_prio_credits)
+{
+ u32 misccpctl;
+
+ /*
+ * WaProgramL3SqcReg1Default:bdw
+ * WaTempDisableDOPClkGating:bdw
+ * For CHV see gfxspecs/Related Documents/Performance Guide/
+ * LSQC Setting Recommendations[CHV,BXT].
+ */
+ misccpctl = I915_READ(GEN7_MISCCPCTL);
+ I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
+
+ I915_WRITE(GEN8_L3SQCREG1,
+ L3_GENERAL_PRIO_CREDITS(general_prio_credits) |
+ L3_HIGH_PRIO_CREDITS(high_prio_credits));
+
+ /*
+ * Wait at least 100 clocks before re-enabling clock gating.
+ * See the definition of L3SQCREG1 in BSpec.
+ */
+ POSTING_READ(GEN8_L3SQCREG1);
+ udelay(1);
+ I915_WRITE(GEN7_MISCCPCTL, misccpctl);
+}
+
static void broadwell_init_clock_gating(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
enum pipe pipe;
- uint32_t misccpctl;
ilk_init_lp_watermarks(dev);
@@ -6704,21 +6731,7 @@ static void broadwell_init_clock_gating(struct drm_device *dev)
I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
- /*
- * WaProgramL3SqcReg1Default:bdw
- * WaTempDisableDOPClkGating:bdw
- */
- misccpctl = I915_READ(GEN7_MISCCPCTL);
- I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
- I915_WRITE(GEN8_L3SQCREG1, L3_GENERAL_PRIO_CREDITS(30) |
- L3_HIGH_PRIO_CREDITS(2));
- /*
- * Wait at least 100 clocks before re-enabling clock gating. See
- * the definition of L3SQCREG1 in BSpec.
- */
- POSTING_READ(GEN8_L3SQCREG1);
- udelay(1);
- I915_WRITE(GEN7_MISCCPCTL, misccpctl);
+ gen8_set_l3sqc_credits(dev_priv, 30, 2);
/*
* WaGttCachingOffByDefault:bdw
@@ -6988,6 +7001,8 @@ static void cherryview_init_clock_gating(struct drm_device *dev)
I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
+ gen8_set_l3sqc_credits(dev_priv, 38, 2);
+
/*
* GTT cache may not work with big pages, so if those
* are ever enabled GTT cache may need to be disabled.
--
2.5.0
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