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

[Tiago Vignatti <tiago.vignatti@intel.com>]

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?

Thanks,

Tiago

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