[PATCH v6 4/5] drm/i915: Implement end_cpu_access

[Tiago Vignatti]

On 12/18/2015 05:02 PM, Tiago Vignatti wrote:
> On 12/17/2015 06:01 AM, Chris Wilson wrote:
>> On Wed, Dec 16, 2015 at 08:25:36PM -0200, Tiago Vignatti wrote:
>>> This function is meant to be used with dma-buf mmap, when finishing
>>> the CPU
>>> access of the mapped pointer.
>>>
>>> +static void i915_gem_end_cpu_access(struct dma_buf *dma_buf, enum
>>> dma_data_direction direction)
>>> +{
>>> +    struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
>>> +    struct drm_device *dev = obj->base.dev;
>>> +    struct drm_i915_private *dev_priv = to_i915(dev);
>>> +    bool was_interruptible, write = (direction == DMA_BIDIRECTIONAL
>>> || direction == DMA_TO_DEVICE);
>>> +    int ret;
>>> +
>>> +    mutex_lock(&dev->struct_mutex);
>>> +    was_interruptible = dev_priv->mm.interruptible;
>>> +    dev_priv->mm.interruptible = false;
>>> +
>>> +    ret = i915_gem_object_set_to_gtt_domain(obj, write);
>>
>> This only needs to pass .write=false. The dma-buf direction is
>> only for the period of the user access, and we are now flushing the
>> caches. This is equivalent to the sw-finish ioctl and ideally we just
>> want the i915_gem_object_flush_cpu_write_domain().
>
> in fact the only usage so far I found for end_cpu_access is when the
> pinned buffer is scanout out. Should I pretty much copy sw-finish in
> end_cpu_access then?

And do you think it's okay to declare 
i915_gem_object_flush_cpu_write_domain outside its file's only scope?

Tiago