drm: omapdrm: add lock for fb pinning

Before atomic modesetting omap_framebuffer_pin() and
omap_framebuffer_unpin() were always called with modesetting locks
taken. With atomic modesetting support this is no longer the case, and
we need locking to protect the pin_count and the paddr, as multiple
threads may pin the same fb concurrently.

This patch adds a mutex to struct omap_framebuffer, and uses it in
omap_framebuffer_pin() and omap_framebuffer_unpin().

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_fb.c b/drivers/gpu/drm/omapdrm/omap_fb.c
index e505140a8782..0b967e76df1a 100644
--- a/drivers/gpu/drm/omapdrm/omap_fb.c
+++ b/drivers/gpu/drm/omapdrm/omap_fb.c
@@ -89,6 +89,8 @@ struct omap_framebuffer {
         int pin_count;
         const struct format *format;
         struct plane planes[4];
+        /* lock for pinning (pin_count and planes.paddr) */
+        struct mutex lock;
 };
 
 static int omap_framebuffer_create_handle(struct drm_framebuffer *fb,
@@ -250,8 +252,11 @@ int omap_framebuffer_pin(struct drm_framebuffer *fb)
         struct omap_framebuffer *omap_fb = to_omap_framebuffer(fb);
         int ret, i, n = drm_format_num_planes(fb->pixel_format);
 
+        mutex_lock(&omap_fb->lock);
+
         if (omap_fb->pin_count > 0) {
                 omap_fb->pin_count++;
+                mutex_unlock(&omap_fb->lock);
                 return 0;
         }
 
@@ -265,6 +270,8 @@ int omap_framebuffer_pin(struct drm_framebuffer *fb)
 
         omap_fb->pin_count++;
 
+        mutex_unlock(&omap_fb->lock);
+
         return 0;
 
 fail:
@@ -274,6 +281,8 @@ fail:
                 plane->paddr = 0;
         }
 
+        mutex_unlock(&omap_fb->lock);
+
         return ret;
 }
 
@@ -283,10 +292,14 @@ int omap_framebuffer_unpin(struct drm_framebuffer *fb)
         struct omap_framebuffer *omap_fb = to_omap_framebuffer(fb);
         int ret, i, n = drm_format_num_planes(fb->pixel_format);
 
+        mutex_lock(&omap_fb->lock);
+
         omap_fb->pin_count--;
 
-        if (omap_fb->pin_count > 0)
+        if (omap_fb->pin_count > 0) {
+                mutex_unlock(&omap_fb->lock);
                 return 0;
+        }
 
         for (i = 0; i < n; i++) {
                 struct plane *plane = &omap_fb->planes[i];
@@ -296,9 +309,12 @@ int omap_framebuffer_unpin(struct drm_framebuffer *fb)
                 plane->paddr = 0;
         }
 
+        mutex_unlock(&omap_fb->lock);
+
         return 0;
 
 fail:
+        mutex_unlock(&omap_fb->lock);
         return ret;
 }
 
@@ -411,6 +427,7 @@ struct drm_framebuffer *omap_framebuffer_init(struct drm_device *dev,
 
         fb = &omap_fb->base;
         omap_fb->format = format;
+        mutex_init(&omap_fb->lock);
 
         for (i = 0; i < n; i++) {
                 struct plane *plane = &omap_fb->planes[i];