drm/i915/skl: Tune IZ hashing when subslices are unbalanced
When one EU is disabled in a particular subslice, we can tune how the
work is spread between subslices to improve EU utilization.
v2: - Use a bitfield to record which subslice(s) has(have) 7 EUs. That
will also make the machinery work if several sublices have 7 EUs.
(Jeff Mcgee)
- Only apply the different hashing algorithm if the slice is
effectively unbalanced by checking there's a single subslice with
7 EUs. (Jeff Mcgee)
v3: Fix typo in comment (Jeff Mcgee)
Issue: VIZ-3845
Cc: Jeff Mcgee <jeff.mcgee@intel.com>
Reviewed-by: Jeff Mcgee <jeff.mcgee@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 9a365b4..f9992ca 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -650,13 +650,24 @@
continue;
for (ss = 0; ss < ss_max; ss++) {
+ u32 n_disabled;
+
if (ss_disable & (0x1 << ss))
/* skip disabled subslice */
continue;
- info->eu_total += eu_max -
- hweight8(eu_disable[s] >>
- (ss * eu_max));
+ n_disabled = hweight8(eu_disable[s] >>
+ (ss * eu_max));
+
+ /*
+ * Record which subslice(s) has(have) 7 EUs. we
+ * can tune the hash used to spread work among
+ * subslices if they are unbalanced.
+ */
+ if (eu_max - n_disabled == 7)
+ info->subslice_7eu[s] |= 1 << ss;
+
+ info->eu_total += eu_max - n_disabled;
}
}
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 61d41ab..4280d0b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -700,6 +700,8 @@
u8 subslice_per_slice;
u8 eu_total;
u8 eu_per_subslice;
+ /* For each slice, which subslice(s) has(have) 7 EUs (bitfield)? */
+ u8 subslice_7eu[3];
u8 has_slice_pg:1;
u8 has_subslice_pg:1;
u8 has_eu_pg:1;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5fab90c..c212411 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1351,6 +1351,8 @@
#define GEN6_WIZ_HASHING_16x4 GEN6_WIZ_HASHING(1, 0)
#define GEN6_WIZ_HASHING_MASK GEN6_WIZ_HASHING(1, 1)
#define GEN6_TD_FOUR_ROW_DISPATCH_DISABLE (1 << 5)
+#define GEN9_IZ_HASHING_MASK(slice) (0x3 << (slice * 2))
+#define GEN9_IZ_HASHING(slice, val) ((val) << (slice * 2))
#define GFX_MODE 0x02520
#define GFX_MODE_GEN7 0x0229c
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 4570fe1..665985d 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1002,6 +1002,49 @@
return 0;
}
+static int skl_tune_iz_hashing(struct intel_engine_cs *ring)
+{
+ struct drm_device *dev = ring->dev;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ u8 vals[3] = { 0, 0, 0 };
+ unsigned int i;
+
+ for (i = 0; i < 3; i++) {
+ u8 ss;
+
+ /*
+ * Only consider slices where one, and only one, subslice has 7
+ * EUs
+ */
+ if (hweight8(dev_priv->info.subslice_7eu[i]) != 1)
+ continue;
+
+ /*
+ * subslice_7eu[i] != 0 (because of the check above) and
+ * ss_max == 4 (maximum number of subslices possible per slice)
+ *
+ * -> 0 <= ss <= 3;
+ */
+ ss = ffs(dev_priv->info.subslice_7eu[i]) - 1;
+ vals[i] = 3 - ss;
+ }
+
+ if (vals[0] == 0 && vals[1] == 0 && vals[2] == 0)
+ return 0;
+
+ /* Tune IZ hashing. See intel_device_info_runtime_init() */
+ WA_SET_FIELD_MASKED(GEN7_GT_MODE,
+ GEN9_IZ_HASHING_MASK(2) |
+ GEN9_IZ_HASHING_MASK(1) |
+ GEN9_IZ_HASHING_MASK(0),
+ GEN9_IZ_HASHING(2, vals[2]) |
+ GEN9_IZ_HASHING(1, vals[1]) |
+ GEN9_IZ_HASHING(0, vals[0]));
+
+ return 0;
+}
+
+
static int skl_init_workarounds(struct intel_engine_cs *ring)
{
struct drm_device *dev = ring->dev;
@@ -1014,7 +1057,7 @@
WA_SET_BIT_MASKED(HIZ_CHICKEN,
BDW_HIZ_POWER_COMPILER_CLOCK_GATING_DISABLE);
- return 0;
+ return skl_tune_iz_hashing(ring);
}
int init_workarounds_ring(struct intel_engine_cs *ring)