[Intel-gfx] [PATCH] drm/i915: Report enabled slices on Haswell GT3

[Rodrigo Vivi]

Batchbuffers constructed by userspace can conditionalise their URB
allocations through the use of the MI_SET_PREDICATE command. This
command can read the MI_PREDICATE_RESULT_2 register to see how many
slices are enabled on GT3, and by virtue of the result, scale their
memory allocations to fit enabled memory.

Of course, this only works if the kernel sets the appropriate bit in the
register first.

v2: Better commit subject and message by Chris Wilson.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Credits-by: Yejun Guo <yejun.guo at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 2 ++
 drivers/gpu/drm/i915/i915_gem.c | 5 +++++
 drivers/gpu/drm/i915/i915_reg.h | 5 +++++
 3 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 14299a4..9e25079 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1519,6 +1519,8 @@ struct drm_i915_file_private {
 				 ((dev)->pci_device & 0xFF00) == 0x0C00)
 #define IS_ULT(dev)		(IS_HASWELL(dev) && \
 				 ((dev)->pci_device & 0xFF00) == 0x0A00)
+#define IS_HSW_GT3(dev)		(IS_HASWELL(dev) && \
+				 ((dev)->pci_device & 0x00F0) == 0x0020)
 
 /*
  * The genX designation typically refers to the render engine, so render
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index f705314..d88c8cb 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4328,6 +4328,11 @@ i915_gem_init_hw(struct drm_device *dev)
 	if (dev_priv->ellc_size)
 		I915_WRITE(HSW_IDICR, I915_READ(HSW_IDICR) | IDIHASHMSK(0xf));
 
+	if (IS_HSW_GT3(dev))
+		I915_WRITE(MI_PREDICATE_RESULT_2, LOWER_SLICE_ENABLED);
+	else
+		I915_WRITE(MI_PREDICATE_RESULT_2, LOWER_SLICE_DISABLED);
+
 	if (HAS_PCH_NOP(dev)) {
 		u32 temp = I915_READ(GEN7_MSG_CTL);
 		temp &= ~(WAIT_FOR_PCH_FLR_ACK | WAIT_FOR_PCH_RESET_ACK);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 53d0e70..2ab0de6 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -278,6 +278,11 @@
 #define  MI_SEMAPHORE_SYNC_VVE	    (1<<16) /* VECS wait for VCS  (VEVSYNC) */
 #define  MI_SEMAPHORE_SYNC_RVE	    (2<<16) /* VECS wait for RCS  (VERSYNC) */
 #define  MI_SEMAPHORE_SYNC_INVALID  (3<<16)
+
+#define MI_PREDICATE_RESULT_2	(0x2214)
+#define  LOWER_SLICE_ENABLED	(1<<0)
+#define  LOWER_SLICE_DISABLED	(0<<0)
+
 /*
  * 3D instructions used by the kernel
  */
-- 
1.8.1.4