drm: renesas: shmobile: Wait for page flip when turning CRTC off

Turning a CRTC off will prevent a queued page flip from ever completing,
potentially confusing userspace.  Wait for queued page flips to complete
before turning the CRTC off to avoid this.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/c97d5859c43fa36043c61de28d67688ebe345092.1694767209.git.geert+renesas@glider.be

diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
index 0adf5d33ba31695e8f342b7bc82d9b6f0fe8d908..20adb9d2fa1782502487897ee0dbbe36e2e37d41 100644 (file)
--- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
+++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.c
@@ -50,11 +50,40 @@ void shmob_drm_crtc_finish_page_flip(struct shmob_drm_crtc *scrtc)
        scrtc->event = NULL;
        if (event) {
                drm_crtc_send_vblank_event(&scrtc->base, event);
+               wake_up(&scrtc->flip_wait);
                drm_crtc_vblank_put(&scrtc->base);
        }
        spin_unlock_irqrestore(&dev->event_lock, flags);
 }
 
+static bool shmob_drm_crtc_page_flip_pending(struct shmob_drm_crtc *scrtc)
+{
+       struct drm_device *dev = scrtc->base.dev;
+       unsigned long flags;
+       bool pending;
+
+       spin_lock_irqsave(&dev->event_lock, flags);
+       pending = scrtc->event != NULL;
+       spin_unlock_irqrestore(&dev->event_lock, flags);
+
+       return pending;
+}
+
+static void shmob_drm_crtc_wait_page_flip(struct shmob_drm_crtc *scrtc)
+{
+       struct drm_crtc *crtc = &scrtc->base;
+       struct shmob_drm_device *sdev = to_shmob_device(crtc->dev);
+
+       if (wait_event_timeout(scrtc->flip_wait,
+                              !shmob_drm_crtc_page_flip_pending(scrtc),
+                              msecs_to_jiffies(50)))
+               return;
+
+       dev_warn(sdev->dev, "page flip timeout\n");
+
+       shmob_drm_crtc_finish_page_flip(scrtc);
+}
+
 /* -----------------------------------------------------------------------------
  * CRTC
  */
@@ -253,6 +282,12 @@ static void shmob_drm_crtc_stop(struct shmob_drm_crtc *scrtc)
        if (!scrtc->started)
                return;
 
+       /*
+        * Wait for page flip completion before stopping the CRTC as userspace
+        * expects page flips to eventually complete.
+        */
+       shmob_drm_crtc_wait_page_flip(scrtc);
+
        /* Stop the LCDC. */
        shmob_drm_crtc_start_stop(scrtc, false);
 
@@ -463,6 +498,8 @@ int shmob_drm_crtc_create(struct shmob_drm_device *sdev)
        unsigned int i;
        int ret;
 
+       init_waitqueue_head(&sdev->crtc.flip_wait);
+
        sdev->crtc.dpms = DRM_MODE_DPMS_OFF;
 
        primary = shmob_drm_plane_create(sdev, DRM_PLANE_TYPE_PRIMARY, 0);

diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.h b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.h
index 2c6d7541427581a6bff4e608cdb465e745d1ae45..b9863e026e8a9b8353ecff384fb2ec7c59af6a50 100644 (file)
--- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.h
+++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_crtc.h
@@ -14,6 +14,8 @@
 #include <drm/drm_connector.h>
 #include <drm/drm_encoder.h>
 
+#include <linux/wait.h>
+
 #include <video/videomode.h>
 
 struct drm_pending_vblank_event;
@@ -24,6 +26,7 @@ struct shmob_drm_crtc {
        struct drm_crtc base;
 
        struct drm_pending_vblank_event *event;
+       wait_queue_head_t flip_wait;
        int dpms;
 
        const struct shmob_drm_format_info *format;