drm/omap: fix race issue when unloading omapdrm

At module unload, omap_fbdev_free() gets called which releases the
framebuffers. However, the framebuffers are still used by crtcs, and
will be released only later at vsync. The driver doesn't wait for this,
and goes on to release the rest of the resources, which often
causes a crash.

This patchs adds a omap_crtc_flush() function which waits until the crtc
has finished with its apply queue and page flips.

The function utilizes a simple polling while-loop, as the performance is
not an issue here.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c b/drivers/gpu/drm/omapdrm/omap_crtc.c
index 0acbe62901d..161a74a3ac5 100644
--- a/drivers/gpu/drm/omapdrm/omap_crtc.c
+++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
@@ -621,6 +621,25 @@ static void omap_crtc_post_apply(struct omap_drm_apply *apply)
 	/* nothing needed for post-apply */
 }
 
+void omap_crtc_flush(struct drm_crtc *crtc)
+{
+	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
+	int loops = 0;
+
+	while (!list_empty(&omap_crtc->pending_applies) ||
+		!list_empty(&omap_crtc->queued_applies) ||
+		omap_crtc->event || omap_crtc->old_fb) {
+
+		if (++loops > 10) {
+			dev_err(crtc->dev->dev,
+				"omap_crtc_flush() timeout\n");
+			break;
+		}
+
+		schedule_timeout_uninterruptible(msecs_to_jiffies(20));
+	}
+}
+
 static const char *channel_names[] = {
 		[OMAP_DSS_CHANNEL_LCD] = "lcd",
 		[OMAP_DSS_CHANNEL_DIGIT] = "tv",