drm/i915: Use vblank worker to unpin old legacy cursor fb safely

The cursor hardware only does sync updates, and thus the hardware
will be scanning out from the old fb until the next start of vblank.
So in order to make the legacy cursor fastpath actually safe we
should not unpin the old fb until we're sure the hardware has
ceased accessing it. The simplest approach is to just use a vblank
work here to do the delayed unpin.

Not 100% sure it's a good idea to put this onto the same high
priority vblank worker as eg. our timing critical gamma updates.
But let's keep it simple for now, and it we later discover that
this is causing problems we can think about adding a lower
priority worker for such things.

This patch is slightly reworked by Maarten

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522053341.137592-3-maarten.lankhorst@linux.intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_cursor.c b/drivers/gpu/drm/i915/display/intel_cursor.c
index 2bd8d02f87034f920cf3963fcd76178e3058d0c5..1c5bc3cf4a6883ee51722574f139155d49e849ef 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_cursor.c
+++ b/drivers/gpu/drm/i915/display/intel_cursor.c
@@ -761,6 +761,17 @@ static bool intel_cursor_format_mod_supported(struct drm_plane *_plane,
        return format == DRM_FORMAT_ARGB8888;
 }
 
+static void intel_cursor_unpin_work(struct kthread_work *base)
+{
+       struct drm_vblank_work *work = to_drm_vblank_work(base);
+       struct intel_plane_state *plane_state =
+               container_of(work, typeof(*plane_state), unpin_work);
+       struct intel_plane *plane = to_intel_plane(plane_state->uapi.plane);
+
+       intel_plane_unpin_fb(plane_state);
+       intel_plane_destroy_state(&plane->base, &plane_state->uapi);
+}
+
 static int
 intel_legacy_cursor_update(struct drm_plane *_plane,
                           struct drm_crtc *_crtc,
@@ -904,14 +915,25 @@ intel_legacy_cursor_update(struct drm_plane *_plane,
 
        intel_psr_unlock(crtc_state);
 
-       intel_plane_unpin_fb(old_plane_state);
+       if (old_plane_state->ggtt_vma != new_plane_state->ggtt_vma) {
+               drm_vblank_work_init(&old_plane_state->unpin_work, &crtc->base,
+                                    intel_cursor_unpin_work);
+
+               drm_vblank_work_schedule(&old_plane_state->unpin_work,
+                                        drm_crtc_accurate_vblank_count(&crtc->base) + 1,
+                                        false);
+
+               old_plane_state = NULL;
+       } else {
+               intel_plane_unpin_fb(old_plane_state);
+       }
 
 out_free:
        if (new_crtc_state)
                intel_crtc_destroy_state(&crtc->base, &new_crtc_state->uapi);
        if (ret)
                intel_plane_destroy_state(&plane->base, &new_plane_state->uapi);
-       else
+       else if (old_plane_state)
                intel_plane_destroy_state(&plane->base, &old_plane_state->uapi);
        return ret;
 

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index c782e65a7123bef881cb9f9aeb487ec78db6c8bb..c2c388212e2eaafe5879c1999a527c15626b2794 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -68,6 +68,7 @@
 #include "intel_crtc_state_dump.h"
 #include "intel_cursor_regs.h"
 #include "intel_cx0_phy.h"
+#include "intel_cursor.h"
 #include "intel_ddi.h"
 #include "intel_de.h"
 #include "intel_display_driver.h"
@@ -7020,6 +7021,8 @@ static void intel_commit_modeset_disables(struct intel_atomic_state *state)
                        continue;
 
                intel_crtc_disable_planes(state, crtc);
+
+               drm_vblank_work_flush_all(&crtc->base);
        }
 
        /* Only disable port sync and MST slaves */

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index ae069993913f4276d86fc4b599766fd6be96001e..8713835e2307cef0db583788194bda42d1c910ac 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -744,6 +744,9 @@ struct intel_plane_state {
        struct intel_fb_view view;
        u32 phys_dma_addr; /* for cursor_needs_physical */
 
+       /* for legacy cursor fb unpin */
+       struct drm_vblank_work unpin_work;
+
        /* Plane pxp decryption state */
        bool decrypt;