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>

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 @@ int omap_framebuffer_pin(struct drm_framebuffer *fb)
 		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];