drm/omap: add pin refcounting to omap_framebuffer

omap_framebuffer_pin() and omap_framebuffer_unpin() are currently
broken, as they cannot be called multiple times (i.e. pin, pin, unpin,
unpin), which is what happens in certain cases. This issue causes the
driver to possibly use 0 as an address for a displayed buffer, leading
to OCP error from DSS.

This patch fixes the issue by adding a simple pin_count, used to track
the number of pins.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_fb.c b/drivers/gpu/drm/omapdrm/omap_fb.c
index 45dd9eed9c57..d1e5f6da30d4 100644
--- a/drivers/gpu/drm/omapdrm/omap_fb.c
+++ b/drivers/gpu/drm/omapdrm/omap_fb.c
@@ -86,6 +86,7 @@ struct plane {
 
 struct omap_framebuffer {
         struct drm_framebuffer base;
+        int pin_count;
         const struct format *format;
         struct plane planes[4];
 };
@@ -249,6 +250,11 @@ 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);
 
+        if (omap_fb->pin_count > 0) {
+                omap_fb->pin_count++;
+                return 0;
+        }
+
         for (i = 0; i < n; i++) {
                 struct plane *plane = &omap_fb->planes[i];
                 ret = omap_gem_get_paddr(plane->bo, &plane->paddr, true);
@@ -257,6 +263,8 @@ int omap_framebuffer_pin(struct drm_framebuffer *fb)
                 omap_gem_dma_sync(plane->bo, DMA_TO_DEVICE);
         }
 
+        omap_fb->pin_count++;
+
         return 0;
 
 fail:
@@ -275,6 +283,11 @@ 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);
 
+        omap_fb->pin_count--;
+
+        if (omap_fb->pin_count > 0)
+                return 0;
+
         for (i = 0; i < n; i++) {
                 struct plane *plane = &omap_fb->planes[i];
                 ret = omap_gem_put_paddr(plane->bo);