Re: [PATCH 3/3] drm/amd/display: Skip modeset for front porch change

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On 2021-01-24 11:00 p.m., Aurabindo Pillai wrote:


On 2021-01-21 2:05 p.m., Kazlauskas, Nicholas wrote:
On 2021-01-19 10:50 a.m., Aurabindo Pillai wrote:
[Why]
A seamless transition between modes can be performed if the new incoming
mode has the same timing parameters as the optimized mode on a display with a
variable vtotal min/max.

Smooth video playback usecases can be enabled with this seamless transition by
switching to a new mode which has a refresh rate matching the video.

[How]
Skip full modeset if userspace requested a compatible freesync mode which only
differs in the front porch timing from the current mode.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
Acked-by: Christian König <christian.koenig@xxxxxxx>
---
  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 233 +++++++++++++++---
  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |   1 +
  2 files changed, 198 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index aaef2fb528fd..d66494cdd8c8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -213,6 +213,9 @@ static bool amdgpu_dm_psr_disable_all(struct amdgpu_display_manager *dm);
  static const struct drm_format_info *
  amd_get_format_info(const struct drm_mode_fb_cmd2 *cmd);
+static bool
+is_timing_unchanged_for_freesync(struct drm_crtc_state *old_crtc_state,
+                 struct drm_crtc_state *new_crtc_state);
  /*
   * dm_vblank_get_counter
   *
@@ -4940,7 +4943,8 @@ static void fill_stream_properties_from_drm_display_mode(
      const struct drm_connector *connector,
      const struct drm_connector_state *connector_state,
      const struct dc_stream_state *old_stream,
-    int requested_bpc)
+    int requested_bpc,
+    bool is_in_modeset)
  {
      struct dc_crtc_timing *timing_out = &stream->timing;
      const struct drm_display_info *info = &connector->display_info;
@@ -4995,19 +4999,28 @@ static void fill_stream_properties_from_drm_display_mode(
          timing_out->hdmi_vic = hv_frame.vic;
      }
-    timing_out->h_addressable = mode_in->crtc_hdisplay;
-    timing_out->h_total = mode_in->crtc_htotal;
-    timing_out->h_sync_width =
-        mode_in->crtc_hsync_end - mode_in->crtc_hsync_start;
-    timing_out->h_front_porch =
-        mode_in->crtc_hsync_start - mode_in->crtc_hdisplay;
-    timing_out->v_total = mode_in->crtc_vtotal;
-    timing_out->v_addressable = mode_in->crtc_vdisplay;
-    timing_out->v_front_porch =
-        mode_in->crtc_vsync_start - mode_in->crtc_vdisplay;
-    timing_out->v_sync_width =
-        mode_in->crtc_vsync_end - mode_in->crtc_vsync_start;
-    timing_out->pix_clk_100hz = mode_in->crtc_clock * 10;
+    if (is_in_modeset) {
+        timing_out->h_addressable = mode_in->hdisplay;
+        timing_out->h_total = mode_in->htotal;
+        timing_out->h_sync_width = mode_in->hsync_end - mode_in->hsync_start; +        timing_out->h_front_porch = mode_in->hsync_start - mode_in->hdisplay;
+        timing_out->v_total = mode_in->vtotal;
+        timing_out->v_addressable = mode_in->vdisplay;
+        timing_out->v_front_porch = mode_in->vsync_start - mode_in->vdisplay; +        timing_out->v_sync_width = mode_in->vsync_end - mode_in->vsync_start;
+        timing_out->pix_clk_100hz = mode_in->clock * 10;
+    } else {
+        timing_out->h_addressable = mode_in->crtc_hdisplay;
+        timing_out->h_total = mode_in->crtc_htotal;
+        timing_out->h_sync_width = mode_in->crtc_hsync_end - mode_in->crtc_hsync_start; +        timing_out->h_front_porch = mode_in->crtc_hsync_start - mode_in->crtc_hdisplay;
+        timing_out->v_total = mode_in->crtc_vtotal;
+        timing_out->v_addressable = mode_in->crtc_vdisplay;
+        timing_out->v_front_porch = mode_in->crtc_vsync_start - mode_in->crtc_vdisplay; +        timing_out->v_sync_width = mode_in->crtc_vsync_end - mode_in->crtc_vsync_start;
+        timing_out->pix_clk_100hz = mode_in->crtc_clock * 10;
+    }
+

Not sure if I commented on this last time but I don't really understand what this is_in_modeset logic is supposed to be doing here.

This is so because create_stream_for_link() that ends up calling this function has two callers, one which is for stream validation in which the created stream is immediately discarded. The other is during modeset. Depending on these two cases, we want to copy the right timing parameters. With this method, major refactor wasn't necessary with the upper layers.

I don't understand why the timing parameters would change between what we validated and what we're planning on applying to the hardware. I think we should be validating the same thing in both cases, especially if it's for something internal like DC stream timing.



We should be modifying crtc_vsync_* for the generated modes, no? Not just the vsync_* parameters.

This is already handled with:

     if (!dm_state)
         drm_mode_set_crtcinfo(&mode, 0);

     if (dm_state && is_fs_vid_mode)
         drm_mode_set_crtcinfo(&saved_mode, 0);


OK, that's fine then.


      timing_out->aspect_ratio = get_aspect_ratio(mode_in);
      stream->output_color_space = get_output_color_space(timing_out);
@@ -5227,6 +5240,33 @@ get_highest_refresh_rate_mode(struct amdgpu_dm_connector *aconnector,
      return m_pref;
  }
+static bool is_freesync_video_mode(struct drm_display_mode *mode,
+                   struct amdgpu_dm_connector *aconnector)
+{
+    struct drm_display_mode *high_mode;
+    int timing_diff;
+
+    high_mode = get_highest_refresh_rate_mode(aconnector, false);
+    if (!high_mode || !mode)
+        return false;
+
+    timing_diff = high_mode->vtotal - mode->vtotal;
+
+    if (high_mode->clock == 0 || high_mode->clock != mode->clock ||
+        high_mode->hdisplay != mode->hdisplay ||
+        high_mode->vdisplay != mode->vdisplay ||
+        high_mode->hsync_start != mode->hsync_start ||
+        high_mode->hsync_end != mode->hsync_end ||
+        high_mode->htotal != mode->htotal ||
+        high_mode->hskew != mode->hskew ||
+        high_mode->vscan != mode->vscan ||
+        high_mode->vsync_start - mode->vsync_start != timing_diff ||
+        high_mode->vsync_end - mode->vsync_end != timing_diff)
+        return false;
+    else
+        return true;
+}
+
  static struct dc_stream_state *
  create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
                 const struct drm_display_mode *drm_mode,
@@ -5240,15 +5280,21 @@ create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
          dm_state ? &dm_state->base : NULL;
      struct dc_stream_state *stream = NULL;
      struct drm_display_mode mode = *drm_mode;
+    struct drm_display_mode saved_mode;
+    struct drm_display_mode *freesync_mode = NULL;
      bool native_mode_found = false;
      bool scale = dm_state ? (dm_state->scaling != RMX_OFF) : false;
      int mode_refresh;
      int preferred_refresh = 0;
+    bool is_fs_vid_mode = false;
  #if defined(CONFIG_DRM_AMD_DC_DCN)
      struct dsc_dec_dpcd_caps dsc_caps;
      uint32_t link_bandwidth_kbps;
  #endif
      struct dc_sink *sink = NULL;
+
+    memset(&saved_mode, 0, sizeof(saved_mode));
+
      if (aconnector == NULL) {
          DRM_ERROR("aconnector is NULL!\n");
          return stream;
@@ -5301,25 +5347,39 @@ create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
           */
          DRM_DEBUG_DRIVER("No preferred mode found\n");
      } else {
-        decide_crtc_timing_for_drm_display_mode(
+        is_fs_vid_mode = amdgpu_freesync_vid_mode &&
+                 is_freesync_video_mode(&mode, aconnector);
+        if (is_fs_vid_mode) {
+            freesync_mode = get_highest_refresh_rate_mode(aconnector, false);
+            saved_mode = mode;
+            mode = *freesync_mode;
+        } else {
+            decide_crtc_timing_for_drm_display_mode(
                  &mode, preferred_mode,
                  dm_state ? (dm_state->scaling != RMX_OFF) : false);
+        }
+
          preferred_refresh = drm_mode_vrefresh(preferred_mode);
      }
      if (!dm_state)
          drm_mode_set_crtcinfo(&mode, 0);
-    /*
+    if (dm_state && is_fs_vid_mode)
+        drm_mode_set_crtcinfo(&saved_mode, 0);
+
+

Not sure what this above bit is doing here:

(1) We're in atomic check and (2) It's a FS video mode

-> set CRTC modesetting timing parameters?

What's this for?

Without this change, kernel would tell the userspace we're sending one of the freesync mode timing, but actually it would send the optimized mode timing parameter. For instance, if 144Hz is the optimized mode, and the user sets 48Hz, the display settings would reflect the change, but the monitor would still see 144Hz.

Sorry, but I still don't understand why it depends on dm_state here. You're trying to avoid updating crtcinfo in mode validation for some reason?


        /*
      * If scaling is enabled and refresh rate didn't change
      * we copy the vic and polarities of the old timings
      */
-    if (!scale || mode_refresh != preferred_refresh)
-        fill_stream_properties_from_drm_display_mode(stream,
-            &mode, &aconnector->base, con_state, NULL, requested_bpc);
+    if (!(scale && is_fs_vid_mode) || mode_refresh != preferred_refresh)
+        fill_stream_properties_from_drm_display_mode(
+            stream, &mode, &aconnector->base, con_state, NULL,
+            requested_bpc, dm_state ? 1 : 0);
      else
-        fill_stream_properties_from_drm_display_mode(stream,
-            &mode, &aconnector->base, con_state, old_stream, requested_bpc);
+        fill_stream_properties_from_drm_display_mode(
+            stream, &mode, &aconnector->base, con_state, old_stream,
+            requested_bpc, dm_state ? 1 : 0);

I don't see my feedback on previous patches addressed here - isn't it cleaner to just merge the is_scaling/is_fs_vid_mode checks here? The idea is that we're replacing the mode with the primary/preferred in both cases.

Sorry, I must have missed it. Will address this in the next iteration.

Using dm_state as a check for validation / vs atomic check is questionable as well. In practice we're guaranteed to have it today but it might not be clear if there are future changes that it's being used for this purpose here if that changes.

This is because we're reusing this function for testing stream validation by calling it directly with a NULL parameter for dm_state. If this usage is not recommended, then a separate function can be used for just stream validation and this usage of dm_state can be dropped.


Like my comments above I'm not sure why these would differ between validation/commit time - they (ideally) should not.


      stream->timing.flags.DSC = 0;
@@ -5456,6 +5516,7 @@ dm_crtc_duplicate_state(struct drm_crtc *crtc)
      state->abm_level = cur->abm_level;
      state->vrr_supported = cur->vrr_supported;
      state->freesync_config = cur->freesync_config;
+    state->freesync_video_mode = cur->freesync_video_mode;
      state->crc_src = cur->crc_src;
      state->cm_has_degamma = cur->cm_has_degamma;
      state->cm_is_degamma_srgb = cur->cm_is_degamma_srgb;
@@ -7149,7 +7210,7 @@ static void amdgpu_dm_connector_add_freesync_modes(struct drm_connector *connect
      struct amdgpu_dm_connector *amdgpu_dm_connector =
          to_amdgpu_dm_connector(connector);
-    if (!(amdgpu_exp_freesync_vid_mode && edid))
+    if (!(amdgpu_freesync_vid_mode && edid))
          return;
      if (edid->version == 1 && edid->revision > 1) {
@@ -7847,9 +7908,25 @@ static void update_stream_irq_parameters(
      if (new_crtc_state->vrr_supported &&
          config.min_refresh_in_uhz &&
          config.max_refresh_in_uhz) {
-        config.state = new_crtc_state->base.vrr_enabled ?
-            VRR_STATE_ACTIVE_VARIABLE :
-            VRR_STATE_INACTIVE;
+        /*
+         * if freesync compatible mode was set, config.state will be set
+         * in atomic check
+         */
+        if (config.state == VRR_STATE_ACTIVE_FIXED &&
+            config.fixed_refresh_in_uhz && config.max_refresh_in_uhz &&
+            config.min_refresh_in_uhz &&

This condition doesn't need to check max_refresh/min_refresh as it's already checked aboved.

Will fix.

+            (!drm_atomic_crtc_needs_modeset(&new_crtc_state->base) ||
+             new_crtc_state->freesync_video_mode)) {
+            vrr_params.max_refresh_in_uhz = config.max_refresh_in_uhz;
+            vrr_params.min_refresh_in_uhz = config.min_refresh_in_uhz;
+            vrr_params.fixed_refresh_in_uhz = config.fixed_refresh_in_uhz;
+            vrr_params.state = VRR_STATE_ACTIVE_FIXED;
+        } else {
+            config.state = new_crtc_state->base.vrr_enabled ?
+                             VRR_STATE_ACTIVE_VARIABLE :
+                             VRR_STATE_INACTIVE;
+        }
+
      } else {
          config.state = VRR_STATE_UNSUPPORTED;
      }
@@ -8171,7 +8248,8 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
           * as part of commit.
           */
          if (amdgpu_dm_vrr_active(dm_old_crtc_state) !=
-            amdgpu_dm_vrr_active(acrtc_state)) {
+            amdgpu_dm_vrr_active(acrtc_state) ||
+            acrtc_state->freesync_video_mode) {

Do we really need this check here? amdgpu_dm_vrr_active should pick up on VRR_STATE_ACTIVE_FIXED, no? If it doesn't then that should be fixed.

This specifically checks for a change the current and previous state. In both the states, freesync_video_mode can be active. This condition would return false in the absence of additional OR with freesync_video_mode. If freesync_video_mode is active, we want this block of code to get executed. If freesync_video_mode is not active, then comparison with old and new state is sufficient. I can add this logic into another function and keep it cleaner here.


I think acrtc_state->freesync_video_mode is redundant - it doesn't check prev/new, it only checks whether or not it's active. This should be already checked in amdgpu_dm_vrr_active(), and the:

amdgpu_dm_vrr_active(dm_old_crtc_state) != amdgpu_dm_vrr_active(acrtc_state)

should be doing this for you.


              spin_lock_irqsave(&pcrtc->dev->event_lock, flags);
              dc_stream_adjust_vmin_vmax(
                  dm->dc, acrtc_state->stream,
@@ -8442,8 +8520,10 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
                  continue;
              }
-            if (dm_old_crtc_state->stream)
+            if (dm_old_crtc_state->stream) {
                  remove_stream(adev, acrtc, dm_old_crtc_state->stream);
+                dm_old_crtc_state->freesync_video_mode = 0;
+            }
              pm_runtime_get_noresume(dev->dev);
@@ -8454,8 +8534,10 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
          } else if (modereset_required(new_crtc_state)) {
              DRM_DEBUG_DRIVER("Atomic commit: RESET. crtc id %d:[%p]\n", acrtc->crtc_id, acrtc);
              /* i.e. reset mode */
-            if (dm_old_crtc_state->stream)
+            if (dm_old_crtc_state->stream) {
                  remove_stream(adev, acrtc, dm_old_crtc_state->stream);
+                dm_old_crtc_state->freesync_video_mode = 0;
+            }
              mode_set_reset_required = true;
          }
      } /* for_each_crtc_in_state() */
@@ -8867,6 +8949,7 @@ static void get_freesync_config_for_crtc(
              to_amdgpu_dm_connector(new_con_state->base.connector);
      struct drm_display_mode *mode = &new_crtc_state->base.mode;
      int vrefresh = drm_mode_vrefresh(mode);
+    bool fs_vid_mode = false;
      new_crtc_state->vrr_supported = new_con_state->freesync_capable &&
                      vrefresh >= aconnector->min_vfreq &&
@@ -8874,17 +8957,25 @@ static void get_freesync_config_for_crtc(
      if (new_crtc_state->vrr_supported) {
          new_crtc_state->stream->ignore_msa_timing_param = true;
-        config.state = new_crtc_state->base.vrr_enabled ?
-                VRR_STATE_ACTIVE_VARIABLE :
-                VRR_STATE_INACTIVE;
-        config.min_refresh_in_uhz =
-                aconnector->min_vfreq * 1000000;
-        config.max_refresh_in_uhz =
-                aconnector->max_vfreq * 1000000;
+        fs_vid_mode = new_crtc_state->freesync_config.state == VRR_STATE_ACTIVE_FIXED ||
+            new_crtc_state->freesync_video_mode;
+
+        config.min_refresh_in_uhz = aconnector->min_vfreq * 1000000;
+        config.max_refresh_in_uhz = aconnector->max_vfreq * 1000000;
          config.vsif_supported = true;
          config.btr = true;
-    }
+        if (fs_vid_mode) {
+            config.state = VRR_STATE_ACTIVE_FIXED;
+            config.fixed_refresh_in_uhz = new_crtc_state->freesync_config.fixed_refresh_in_uhz;
+            goto out;
+        } else if (new_crtc_state->base.vrr_enabled) {
+            config.state = VRR_STATE_ACTIVE_VARIABLE;
+        } else {
+            config.state = VRR_STATE_INACTIVE;
+        }
+    }
+out:
      new_crtc_state->freesync_config = config;
  }
@@ -8897,6 +8988,51 @@ static void reset_freesync_config_for_crtc(
             sizeof(new_crtc_state->vrr_infopacket));
  }
+static bool
+is_timing_unchanged_for_freesync(struct drm_crtc_state *old_crtc_state,
+                 struct drm_crtc_state *new_crtc_state)
+{
+    struct drm_display_mode old_mode, new_mode;
+
+    if (!old_crtc_state || !new_crtc_state)
+        return false;
+
+    old_mode = old_crtc_state->mode;
+    new_mode = new_crtc_state->mode;
+
+    if (old_mode.clock       == new_mode.clock &&
+        old_mode.hdisplay    == new_mode.hdisplay &&
+        old_mode.vdisplay    == new_mode.vdisplay &&
+        old_mode.htotal      == new_mode.htotal &&
+        old_mode.vtotal      != new_mode.vtotal &&
+        old_mode.hsync_start == new_mode.hsync_start &&
+        old_mode.vsync_start != new_mode.vsync_start &&
+        old_mode.hsync_end   == new_mode.hsync_end &&
+        old_mode.vsync_end   != new_mode.vsync_end &&
+        old_mode.hskew       == new_mode.hskew &&
+        old_mode.vscan       == new_mode.vscan &&
+        (old_mode.vsync_end - old_mode.vsync_start) ==
+        (new_mode.vsync_end - new_mode.vsync_start))
+        return true;
+
+    return false;
+}
+
+static void set_freesync_fixed_config(struct dm_crtc_state *dm_new_crtc_state) {
+    uint64_t num, den, res;
+    struct drm_crtc_state *new_crtc_state = &dm_new_crtc_state->base;
+
+    dm_new_crtc_state->freesync_config.state = VRR_STATE_ACTIVE_FIXED;
+
+    num = (unsigned long long)new_crtc_state->mode.clock * 1000 * 1000000;
+    den = (unsigned long long)new_crtc_state->mode.htotal *
+          (unsigned long long)new_crtc_state->mode.vtotal;
+
+    res = div_u64(num, den);
+    dm_new_crtc_state->freesync_config.fixed_refresh_in_uhz = res;
+    dm_new_crtc_state->freesync_video_mode = true;
+}
+
  static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
                  struct drm_atomic_state *state,
                  struct drm_crtc *crtc,
@@ -8987,6 +9123,11 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
           * TODO: Refactor this function to allow this check to work
           * in all conditions.
           */
+        if (amdgpu_freesync_vid_mode &&
+            dm_new_crtc_state->stream &&
+            is_timing_unchanged_for_freesync(new_crtc_state, old_crtc_state))
+            goto skip_modeset;
+
          if (dm_new_crtc_state->stream &&
              dc_is_stream_unchanged(new_stream, dm_old_crtc_state->stream) &&               dc_is_stream_scaling_unchanged(new_stream, dm_old_crtc_state->stream)) { @@ -9018,6 +9159,26 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
          if (!dm_old_crtc_state->stream)
              goto skip_modeset;
+        if (amdgpu_freesync_vid_mode && dm_new_crtc_state->stream &&
+            is_timing_unchanged_for_freesync(new_crtc_state,
+                             old_crtc_state)) {
+            new_crtc_state->mode_changed = false;
+            DRM_DEBUG_DRIVER(
+                "Mode change not required for front porch change, "
+                "setting mode_changed to %d",
+                new_crtc_state->mode_changed);
+
+            set_freesync_fixed_config(dm_new_crtc_state);
+
+            goto skip_modeset;
+        } else if (amdgpu_freesync_vid_mode && aconnector &&
+               is_freesync_video_mode(&new_crtc_state->mode,
+                          aconnector)) {
+            set_freesync_fixed_config(dm_new_crtc_state);

I don't think this extra check is needed here because we have the one above.

In the second branch, since we call is_freesync_video_mode(), the check with the module parameter was also necessary as this is the triggering point for the VRR api configuration change. Also, the first branch skips the modeset, while the second doesnt. So we cannot club them together. The second branch is for the case when a freesync mode was set accompanied by a modeset. This happens when the previous mode had different base timings and hence a modeset is necessary.


Thanks & Regards,
Aurabindo Pillai


Okay, I understand this block now. Thanks.

Regards,
Nicholas Kazlauskas


Regards,
Nicholas Kazlauskas

+        } else if (dm_new_crtc_state->freesync_video_mode) {
+            dm_new_crtc_state->freesync_video_mode = 0;
+        }
+
          ret = dm_atomic_get_state(state, &dm_state);
          if (ret)
              goto fail;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index 3ea85be9c546..ff4675572125 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -474,6 +474,7 @@ struct dm_crtc_state {
      bool freesync_timing_changed;
      bool freesync_vrr_info_changed;
+    bool freesync_video_mode;
      bool dsc_force_changed;
      bool vrr_supported;





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