drm/omap: use refcount API to track the number of users of dma_addr

This would give us a WARN_ON() if the pin/unpin calls are unbalanced.

Proposed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191010120000.1421-2-jjhiblot@ti.com

diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 08f539e..61caa7a 100644 (file)
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -67,7 +67,7 @@ struct omap_gem_object {
        /**
         * # of users of dma_addr
         */
-       u32 dma_addr_cnt;
+       refcount_t dma_addr_cnt;
 
        /**
         * If the buffer has been imported from a dmabuf the OMAP_DB_DMABUF flag
@@ -773,13 +773,15 @@ int omap_gem_pin(struct drm_gem_object *obj, dma_addr_t *dma_addr)
        mutex_lock(&omap_obj->lock);
 
        if (!omap_gem_is_contiguous(omap_obj) && priv->has_dmm) {
-               if (omap_obj->dma_addr_cnt == 0) {
+               if (refcount_read(&omap_obj->dma_addr_cnt) == 0) {
                        u32 npages = obj->size >> PAGE_SHIFT;
                        enum tiler_fmt fmt = gem2fmt(omap_obj->flags);
                        struct tiler_block *block;
 
                        BUG_ON(omap_obj->block);
 
+                       refcount_set(&omap_obj->dma_addr_cnt, 1);
+
                        ret = omap_gem_attach_pages(obj);
                        if (ret)
                                goto fail;
@@ -813,10 +815,10 @@ int omap_gem_pin(struct drm_gem_object *obj, dma_addr_t *dma_addr)
                        omap_obj->block = block;
 
                        DBG("got dma address: %pad", &omap_obj->dma_addr);
+               } else {
+                       refcount_inc(&omap_obj->dma_addr_cnt);
                }
 
-               omap_obj->dma_addr_cnt++;
-
                *dma_addr = omap_obj->dma_addr;
        } else if (omap_gem_is_contiguous(omap_obj)) {
                *dma_addr = omap_obj->dma_addr;
@@ -846,22 +848,19 @@ void omap_gem_unpin(struct drm_gem_object *obj)
 
        mutex_lock(&omap_obj->lock);
 
-       if (omap_obj->dma_addr_cnt > 0) {
-               omap_obj->dma_addr_cnt--;
-               if (omap_obj->dma_addr_cnt == 0) {
-                       ret = tiler_unpin(omap_obj->block);
-                       if (ret) {
-                               dev_err(obj->dev->dev,
-                                       "could not unpin pages: %d\n", ret);
-                       }
-                       ret = tiler_release(omap_obj->block);
-                       if (ret) {
-                               dev_err(obj->dev->dev,
-                                       "could not release unmap: %d\n", ret);
-                       }
-                       omap_obj->dma_addr = 0;
-                       omap_obj->block = NULL;
+       if (refcount_dec_and_test(&omap_obj->dma_addr_cnt)) {
+               ret = tiler_unpin(omap_obj->block);
+               if (ret) {
+                       dev_err(obj->dev->dev,
+                               "could not unpin pages: %d\n", ret);
+               }
+               ret = tiler_release(omap_obj->block);
+               if (ret) {
+                       dev_err(obj->dev->dev,
+                               "could not release unmap: %d\n", ret);
                }
+               omap_obj->dma_addr = 0;
+               omap_obj->block = NULL;
        }
 
        mutex_unlock(&omap_obj->lock);
@@ -879,7 +878,7 @@ int omap_gem_rotated_dma_addr(struct drm_gem_object *obj, u32 orient,
 
        mutex_lock(&omap_obj->lock);
 
-       if ((omap_obj->dma_addr_cnt > 0) && omap_obj->block &&
+       if ((refcount_read(&omap_obj->dma_addr_cnt) > 0) && omap_obj->block &&
                        (omap_obj->flags & OMAP_BO_TILED)) {
                *dma_addr = tiler_tsptr(omap_obj->block, orient, x, y);
                ret = 0;
@@ -1030,7 +1029,8 @@ void omap_gem_describe(struct drm_gem_object *obj, struct seq_file *m)
 
        seq_printf(m, "%08x: %2d (%2d) %08llx %pad (%2d) %p %4d",
                        omap_obj->flags, obj->name, kref_read(&obj->refcount),
-                       off, &omap_obj->dma_addr, omap_obj->dma_addr_cnt,
+                       off, &omap_obj->dma_addr,
+                       refcount_read(&omap_obj->dma_addr_cnt),
                        omap_obj->vaddr, omap_obj->roll);
 
        if (omap_obj->flags & OMAP_BO_TILED) {
@@ -1093,7 +1093,7 @@ void omap_gem_free_object(struct drm_gem_object *obj)
        mutex_lock(&omap_obj->lock);
 
        /* The object should not be pinned. */
-       WARN_ON(omap_obj->dma_addr_cnt > 0);
+       WARN_ON(refcount_read(&omap_obj->dma_addr_cnt) > 0);
 
        if (omap_obj->pages) {
                if (omap_obj->flags & OMAP_BO_MEM_DMABUF)