Re: [PATCH 1/5] drm/omap: return error if dma_alloc_writecombine fails

[Tomi Valkeinen <tomi.valkeinen@xxxxxx>]

On 18/06/15 17:27, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thursday 18 June 2015 13:10:35 Tomi Valkeinen wrote:
>> On a platform with no TILER (e.g. omap3, am43xx), when the user wants to
>> allocate buffer with flag OMAP_BO_SCANOUT, the buffer needs to be
>> allocated with dma_alloc_writecombine. For some reason the driver does
>> not return an error if that alloc fails, instead it continues without
>> backing memory. This leads to errors later when the user tries to use
>> the buffer.
>>
>> This patch makes the driver return an error if dma_alloc_writecombine
>> fails.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
>> ---
>>  drivers/gpu/drm/omapdrm/omap_gem.c | 12 ++++++++++--
>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c
>> b/drivers/gpu/drm/omapdrm/omap_gem.c index 2ab77801cf5f..51c5635aff62
>> 100644
>> --- a/drivers/gpu/drm/omapdrm/omap_gem.c
>> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c
>> @@ -1392,9 +1392,17 @@ struct drm_gem_object *omap_gem_new(struct drm_device
>> *dev, */
>>  		omap_obj->vaddr =  dma_alloc_writecombine(dev->dev, size,
>>  				&omap_obj->paddr, GFP_KERNEL);
>> -		if (omap_obj->vaddr)
>> -			flags |= OMAP_BO_DMA;
>> +		if (!omap_obj->vaddr) {
>> +			spin_lock(&priv->list_lock);
>> +			list_del(&omap_obj->mm_list);
>> +			spin_unlock(&priv->list_lock);
> 
> Wouldn't it be simpler to move the list_add after the "if ((flags & 
> OMAP_BO_SCANOUT) && !priv->has_dmm)" block ? You could then avoid the 
> list_del.

Thanks, it's cleaner that way:

commit 70a7c80ae9f787031fa3eebc70df024deadde09f (HEAD)
Author: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Date:   Tue Mar 17 15:31:11 2015 +0200

    drm/omap: return error if dma_alloc_writecombine fails
    
    On a platform with no TILER (e.g. omap3, am43xx), when the user wants to
    allocate buffer with flag OMAP_BO_SCANOUT, the buffer needs to be
    allocated with dma_alloc_writecombine. For some reason the driver does
    not return an error if that alloc fails, instead it continues without
    backing memory. This leads to errors later when the user tries to use
    the buffer.
    
    This patch makes the driver return an error if dma_alloc_writecombine
    fails.
    
    Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>

diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 2ab77801cf5f..874eb6dcf94b 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -1378,11 +1378,7 @@ struct drm_gem_object *omap_gem_new(struct drm_device *dev,
 
 	omap_obj = kzalloc(sizeof(*omap_obj), GFP_KERNEL);
 	if (!omap_obj)
-		goto fail;
-
-	spin_lock(&priv->list_lock);
-	list_add(&omap_obj->mm_list, &priv->obj_list);
-	spin_unlock(&priv->list_lock);
+		return NULL;
 
 	obj = &omap_obj->base;
 
@@ -1392,11 +1388,19 @@ struct drm_gem_object *omap_gem_new(struct drm_device *dev,
 		 */
 		omap_obj->vaddr =  dma_alloc_writecombine(dev->dev, size,
 				&omap_obj->paddr, GFP_KERNEL);
-		if (omap_obj->vaddr)
-			flags |= OMAP_BO_DMA;
+		if (!omap_obj->vaddr) {
+			kfree(omap_obj);
 
+			return NULL;
+		}
+
+		flags |= OMAP_BO_DMA;
 	}
 
+	spin_lock(&priv->list_lock);
+	list_add(&omap_obj->mm_list, &priv->obj_list);
+	spin_unlock(&priv->list_lock);
+
 	omap_obj->flags = flags;
 
 	if (flags & OMAP_BO_TILED) {

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