Re: [PATCH] drm/i915/icl: Fix context slice count configuration

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On 29/08/2018 11:54, Tvrtko Ursulin wrote:

On 22/08/2018 17:33, Lionel Landwerlin wrote:
On 22/08/2018 17:18, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Bitfield width for configuring the active slice count has grown in Gen11
so we need to program the GEN8_R_PWR_CLK_STATE accordingly.

Current code was always requesting eight times the number of slices (due writting to a bitfield starting three bits higher than it should). These requests were luckily a) capped by the hardware to the available number of slices, and b) we haven't yet exported the code to ask for reduced slice
configurations.

Due both of the above there was no impact from this incorrect programming
but we should still fix it.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Bspec: 12247
Reported-by: tony.ye@xxxxxxxxx
Suggested-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Cc: tony.ye@xxxxxxxxx
---
  drivers/gpu/drm/i915/i915_reg.h  |  2 ++
  drivers/gpu/drm/i915/intel_lrc.c | 12 ++++++++----
  2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 59d06d0055bb..640f7b774a26 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -344,6 +344,8 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
  #define   GEN8_RPCS_S_CNT_ENABLE    (1 << 18)
  #define   GEN8_RPCS_S_CNT_SHIFT        15
  #define   GEN8_RPCS_S_CNT_MASK        (0x7 << GEN8_RPCS_S_CNT_SHIFT)
+#define   GEN11_RPCS_S_CNT_SHIFT    12
+#define   GEN11_RPCS_S_CNT_MASK        (0x3f << GEN11_RPCS_S_CNT_SHIFT)
  #define   GEN8_RPCS_SS_CNT_ENABLE    (1 << 11)
  #define   GEN8_RPCS_SS_CNT_SHIFT    8
  #define   GEN8_RPCS_SS_CNT_MASK        (0x7 << GEN8_RPCS_SS_CNT_SHIFT) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 36050f085071..43b8b0675ba0 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2501,10 +2501,14 @@ make_rpcs(struct drm_i915_private *dev_priv)
       * enablement.
      */
      if (INTEL_INFO(dev_priv)->sseu.has_slice_pg) {
-        rpcs |= GEN8_RPCS_S_CNT_ENABLE;
-        rpcs |= hweight8(INTEL_INFO(dev_priv)->sseu.slice_mask) <<
-            GEN8_RPCS_S_CNT_SHIFT;
-        rpcs |= GEN8_RPCS_ENABLE;
+        rpcs = hweight8(INTEL_INFO(dev_priv)->sseu.slice_mask);
+
+        if (INTEL_GEN(dev_priv) >= 11)
+            rpcs <<= GEN11_RPCS_S_CNT_SHIFT;
+        else
+            rpcs <<= GEN8_RPCS_S_CNT_SHIFT;
+
+        rpcs |= GEN8_RPCS_ENABLE | GEN8_RPCS_S_CNT_ENABLE;


I don't know if you saw that wording in the documentation :

  "

Note: In ICL, software programs this register as if GT consists of 2 slices with 4 subslices in each slice. Hardware maps this to the 1 slice/8-subslice physical layout.

"


My understanding is that it would make this function a bit more complicated ;)

It also implies that on ICL you cannot select 3 subslices, which is unfortunately what Tony was trying to do.

Maybe some opens need to be raised as to what's possible on ICL.

Happy to r-b this one since we clarified it is fine?

Regards,

Tvrtko


I think there is still an issue here with regard to the subslice programming.
You can only program values in [1, 4].
But because we expose up to 8 subslices, you need to take that mask and alter the slice mask based on its value.

-
Lionel
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