Flushing the fbdev's shadow buffer requires vmap'ing the BO memory, which
in turn requires pinning the BO. While being pinned, the BO cannot be moved
into VRAM for scanout. Consequently, a concurrent modeset operation that
involves the fbdev framebuffer would likely fail.
Resolve this problem be acquiring the modeset lock of the planes that use
the fbdev framebuffer. On non-atomic drivers, also acquire the mode-config
lock. This serializes the flushing of the framebuffer with concurrent
modeset operations.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/gpu/drm/drm_fb_helper.c | 43 +++++++++++++++++++++++++++++++--
1 file changed, 41 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 5a22c744378c..af485c71a42a 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -394,20 +394,59 @@ static void drm_fb_helper_damage_blit_real(struct drm_fb_helper *fb_helper,
static int drm_fb_helper_damage_blit(struct drm_fb_helper *fb_helper,
struct drm_clip_rect *clip)
{
+ struct drm_device *dev = fb_helper->dev;
+ struct drm_framebuffer *fb = fb_helper->fb;
struct drm_client_buffer *buffer = fb_helper->buffer;
+ struct drm_modeset_acquire_ctx ctx;
+ struct drm_framebuffer *plane_fb;
+ struct drm_plane *plane;
struct dma_buf_map map, dst;
int ret;
+ if (!drm_drv_uses_atomic_modeset(dev))
+ mutex_lock(&dev->mode_config.mutex);
+
+ drm_modeset_acquire_init(&ctx, 0);
+
+retry:
+ drm_for_each_plane(plane, dev) {
+ ret = drm_modeset_lock(&plane->mutex, &ctx);
+ if (ret == -EDEADLK) {
+ ret = drm_modeset_backoff(&ctx);
+ if (!ret)
+ goto retry;
+ } else if (ret) {
+ goto out;
+ }
+
+ if (drm_drv_uses_atomic_modeset(dev))
+ plane_fb = plane->state->fb;
+ else
+ plane_fb = plane->fb;
+
+ if (plane_fb != fb) {
+ drm_modeset_unlock(&plane->mutex);
+ continue;
+ }
+ }
+
ret = drm_client_buffer_vmap(buffer, &map);
if (ret)
- return ret;
+ goto out;
dst = map;
drm_fb_helper_damage_blit_real(fb_helper, clip, &dst);
drm_client_buffer_vunmap(buffer);
- return 0;
+out:
+ drm_modeset_drop_locks(&ctx);
+ drm_modeset_acquire_fini(&ctx);
+
+ if (!drm_drv_uses_atomic_modeset(dev))
+ mutex_unlock(&dev->mode_config.mutex);
+
+ return ret;
}
static void drm_fb_helper_damage_work(struct work_struct *work)
--
2.29.2
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