This patch implemnets Workariunds related to display arbitrated memory
bandwidth. These WA are applicabe for all gen-9 based platforms.

Changes since v1:
 - Rebase on top of Paulo's patch series
Changes since v2:
 - Address review comments
 - Rebase/rework as per other patch changes in series

Signed-off-by: Mahesh Kumar <mahesh1.ku...@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h |   9 +++
 drivers/gpu/drm/i915/intel_pm.c | 149 +++++++++++++++++++++++++++++++++++++---
 2 files changed, 149 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 171163c..f8700a6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1193,6 +1193,13 @@ enum intel_sbi_destination {
        SBI_MPHY,
 };
 
+/* SKL+ Watermark arbitrated display bandwidth Workarounds */
+enum watermark_memory_wa {
+       WATERMARK_WA_NONE,
+       WATERMARK_WA_X_TILED,
+       WATERMARK_WA_Y_TILED,
+};
+
 #define QUIRK_PIPEA_FORCE (1<<0)
 #define QUIRK_LVDS_SSC_DISABLE (1<<1)
 #define QUIRK_INVERT_BRIGHTNESS (1<<2)
@@ -1764,6 +1771,8 @@ struct skl_ddb_allocation {
 
 struct skl_wm_values {
        unsigned dirty_pipes;
+       /* any WaterMark memory workaround Required */
+       enum watermark_memory_wa mem_wa;
        struct skl_ddb_allocation ddb;
 };
 
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7c788ac..f42b190 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2889,11 +2889,7 @@ skl_wm_plane_id(const struct intel_plane *plane)
        }
 }
 
-/*
- * FIXME: We still don't have the proper code detect if we need to apply the 
WA,
- * so assume we'll always need it in order to avoid underruns.
- */
-static bool skl_needs_memory_bw_wa(struct intel_atomic_state *state)
+static bool intel_needs_memory_bw_wa(struct intel_atomic_state *state)
 {
        struct drm_i915_private *dev_priv = to_i915(state->base.dev);
 
@@ -3067,7 +3063,7 @@ bool intel_can_enable_sagv(struct drm_atomic_state *state)
 
                latency = dev_priv->wm.skl_latency[level];
 
-               if (skl_needs_memory_bw_wa(intel_state) &&
+               if (intel_needs_memory_bw_wa(intel_state) &&
                    plane->base.state->fb->modifier ==
                    I915_FORMAT_MOD_X_TILED)
                        latency += 15;
@@ -3598,7 +3594,7 @@ static int skl_compute_plane_wm(const struct 
drm_i915_private *dev_priv,
        uint32_t y_min_scanlines;
        struct intel_atomic_state *state =
                to_intel_atomic_state(cstate->base.state);
-       bool apply_memory_bw_wa = skl_needs_memory_bw_wa(state);
+       enum watermark_memory_wa mem_wa;
        bool y_tiled, x_tiled;
 
        if (latency == 0 || !cstate->base.active || 
!intel_pstate->base.visible) {
@@ -3614,7 +3610,8 @@ static int skl_compute_plane_wm(const struct 
drm_i915_private *dev_priv,
                                fb->modifier == I915_FORMAT_MOD_Yf_TILED;
        x_tiled = fb->modifier == I915_FORMAT_MOD_X_TILED;
 
-       if (apply_memory_bw_wa && x_tiled)
+       mem_wa = state->wm_results.mem_wa;
+       if (mem_wa != WATERMARK_WA_NONE && x_tiled)
                latency += 15;
 
        width = drm_rect_width(&intel_pstate->base.src) >> 16;
@@ -3649,7 +3646,7 @@ static int skl_compute_plane_wm(const struct 
drm_i915_private *dev_priv,
                y_min_scanlines = 4;
        }
 
-       if (apply_memory_bw_wa)
+       if (mem_wa == WATERMARK_WA_Y_TILED)
                y_min_scanlines *= 2;
 
        plane_bytes_per_line = width * cpp;
@@ -4078,6 +4075,15 @@ skl_compute_ddb(struct drm_atomic_state *state)
        }
 
        /*
+        * If Watermark workaround is changed we need to recalculate
+        * watermark values for all active pipes
+        */
+       if (intel_state->wm_results.mem_wa != dev_priv->wm.skl_hw.mem_wa) {
+               realloc_pipes = ~0;
+               intel_state->wm_results.dirty_pipes = ~0;
+       }
+
+       /*
         * We're not recomputing for the pipes not included in the commit, so
         * make sure we start with the current state.
         */
@@ -4103,6 +4109,129 @@ skl_compute_ddb(struct drm_atomic_state *state)
 }
 
 static void
+skl_compute_memory_bandwidth_wm_wa(struct drm_atomic_state *state)
+{
+       struct drm_device *dev = state->dev;
+       struct drm_i915_private *dev_priv = to_i915(dev);
+       struct intel_crtc *intel_crtc;
+       struct intel_plane_state *intel_pstate;
+       struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
+       struct memdev_info *memdev_info = &dev_priv->memdev_info;
+       int num_active_pipes;
+       uint32_t max_pipe_bw_kbps, total_pipe_bw_kbps;
+       int display_bw_percentage;
+       bool y_tile_enabled = false;
+
+       if (!intel_needs_memory_bw_wa(intel_state)) {
+               intel_state->wm_results.mem_wa = WATERMARK_WA_NONE;
+               return;
+       }
+
+       if (!memdev_info->valid)
+               goto exit;
+
+       max_pipe_bw_kbps = 0;
+       num_active_pipes = 0;
+       for_each_intel_crtc(dev, intel_crtc) {
+               struct intel_crtc_state *cstate;
+               struct intel_plane *plane;
+               int num_active_planes;
+               uint32_t  max_plane_bw_kbps, pipe_bw_kbps;
+
+               /*
+                * If CRTC is part of current atomic commit, get crtc state from
+                * existing CRTC state. else take the cached CRTC state
+                */
+               cstate = NULL;
+               if (state)
+                       cstate = intel_atomic_get_existing_crtc_state(state,
+                                       intel_crtc);
+               if (!cstate)
+                       cstate = to_intel_crtc_state(intel_crtc->base.state);
+
+               if (!cstate->base.active)
+                       continue;
+
+               num_active_planes = 0;
+               max_plane_bw_kbps = 0;
+               for_each_intel_plane_mask(dev, plane, cstate->base.plane_mask) {
+                       struct drm_framebuffer *fb;
+                       uint32_t plane_bw_kbps;
+                       uint32_t id = skl_wm_plane_id(plane);
+
+                       intel_pstate = NULL;
+                       intel_pstate =
+                               intel_atomic_get_existing_plane_state(state,
+                                                                       plane);
+                       if (!intel_pstate)
+                               intel_pstate =
+                                       to_intel_plane_state(plane->base.state);
+
+                       if (!intel_pstate->base.visible)
+                               continue;
+
+                       if (WARN_ON(!intel_pstate->base.fb))
+                               continue;
+
+                       if (id == PLANE_CURSOR)
+                               continue;
+
+                       fb = intel_pstate->base.fb;
+                       if ((fb->modifier == I915_FORMAT_MOD_Y_TILED ||
+                               fb->modifier == I915_FORMAT_MOD_Yf_TILED))
+                               y_tile_enabled = true;
+
+                       plane_bw_kbps = skl_adjusted_plane_pixel_rate(cstate,
+                                                               intel_pstate);
+                       max_plane_bw_kbps = max(plane_bw_kbps,
+                                                       max_plane_bw_kbps);
+                       num_active_planes++;
+               }
+               pipe_bw_kbps = max_plane_bw_kbps * num_active_planes;
+               max_pipe_bw_kbps = max(pipe_bw_kbps, max_pipe_bw_kbps);
+               num_active_pipes++;
+       }
+
+       total_pipe_bw_kbps = max_pipe_bw_kbps * num_active_pipes;
+
+       display_bw_percentage = DIV_ROUND_UP_ULL(total_pipe_bw_kbps * 100,
+                                               memdev_info->bandwidth_kbps);
+
+       /*
+        * If there is any Ytile plane enabled and arbitrated display
+        * bandwidth > 20% of raw system memory bandwidth
+        * Enale Y-tile related WA
+        *
+        * If memory is dual channel single rank, Xtile limit = 35%, else Xtile
+        * limit = 60%
+        * If there is no Ytile plane enabled and
+        * arbitrated display bandwidth > Xtile limit
+        * Enable X-tile realated WA
+        */
+       if (y_tile_enabled && (display_bw_percentage > 20))
+               intel_state->wm_results.mem_wa = WATERMARK_WA_Y_TILED;
+       else {
+               int x_tile_percentage = 60;
+               enum rank rank = DRAM_RANK_SINGLE;
+
+               if (memdev_info->rank != DRAM_RANK_INVALID)
+                       rank = memdev_info->rank;
+
+               if ((rank == DRAM_RANK_SINGLE) &&
+                                       (memdev_info->num_channels == 2))
+                       x_tile_percentage = 35;
+
+               if (display_bw_percentage > x_tile_percentage)
+                       intel_state->wm_results.mem_wa = WATERMARK_WA_X_TILED;
+       }
+       return;
+
+exit:
+       intel_state->wm_results.mem_wa = WATERMARK_WA_Y_TILED;
+}
+
+
+static void
 skl_copy_wm_for_pipe(struct skl_wm_values *dst,
                     struct skl_wm_values *src,
                     enum pipe pipe)
@@ -4178,6 +4307,8 @@ skl_compute_wm(struct drm_atomic_state *state)
        /* Clear all dirty flags */
        results->dirty_pipes = 0;
 
+       skl_compute_memory_bandwidth_wm_wa(state);
+
        ret = skl_compute_ddb(state);
        if (ret)
                return ret;
-- 
2.10.1

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