[PATCH] drm/omap: fix dma_addr refcounting

[Laurent Pinchart]

Hi Tomi,

Thank you for the patch.

On Thu, Nov 14, 2019 at 10:03:43AM +0200, Tomi Valkeinen wrote:
> cec4fa7511ef7a73eb635834e9d85b25a5b47a98 ("drm/omap: use refcount API to
> track the number of users of dma_addr") changed omap_gem.c to use
> refcounting API to track dma_addr uses.  However, the driver only tracks
> the refcounts for non-contiguous buffers, and the patch didn't fully
> take this in account.
> 
> After the patch, the driver always decreased refcount in omap_gem_unpin,
> instead of decreasing the refcount only for non-contiguous buffers. This
> leads to refcounting mismatch.
> 
> As for the contiguous cases the refcount is never increased, fix this
> issue by returning from omap_gem_unpin if the buffer being unpinned is
> contiguous.

How about adding a Fixes line ?

Fixes: cec4fa7511ef ("drm/omap: use refcount API to track the number of users of dma_addr")

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

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> ---
>  drivers/gpu/drm/omapdrm/omap_gem.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
> index e518d93ca6df..d08ae95ecc0a 100644
> --- a/drivers/gpu/drm/omapdrm/omap_gem.c
> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c
> @@ -843,9 +843,13 @@ int omap_gem_pin(struct drm_gem_object *obj, dma_addr_t *dma_addr)
>   */
>  static void omap_gem_unpin_locked(struct drm_gem_object *obj)
>  {
> +	struct omap_drm_private *priv = obj->dev->dev_private;
>  	struct omap_gem_object *omap_obj = to_omap_bo(obj);
>  	int ret;
>  
> +	if (omap_gem_is_contiguous(omap_obj) || !priv->has_dmm)
> +		return;
> +
>  	if (refcount_dec_and_test(&omap_obj->dma_addr_cnt)) {
>  		ret = tiler_unpin(omap_obj->block);
>  		if (ret) {

-- 
Regards,

Laurent Pinchart