[Mesa-dev] [PATCH 20/26] radeonsi: disable DCC on handle export if expecting write access

[Michel Dänzer]

On 09.03.2016 20:29, Marek Olšák wrote:
> On Wed, Mar 9, 2016 at 7:19 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
>> On 02.03.2016 11:36, Marek Olšák wrote:
>>>
>>> @@ -318,6 +343,13 @@ static boolean r600_texture_get_handle(struct
>>> pipe_screen* screen,
>>>                 res->external_usage = usage;
>>>
>>>                 if (resource->target != PIPE_BUFFER) {
>>> +                       /* Since shader image stores don't support DCC on
>>> VI,
>>> +                        * disable it for external clients that want write
>>> +                        * access.
>>> +                        */
>>> +                       if (usage & PIPE_HANDLE_USAGE_WRITE)
>>> +                               r600_texture_disable_dcc(rscreen, rtex);
>>
>>
>> Have you considered keeping DCC enabled when the user sets the explicit
>> flush flag and having flush_resource decompress for writably-shared
>> resources?
> 
> DCC decompression is a very costly operation and it's better to avoid
> it if possible. Currently, DCC is only supported with non-displayable
> surfaces, but all users of flush_resource (DRI2/3) only get
> displayable surfaces. Thus, the driver doesn't have to worry about
> flush_resource with DCC.

I'm afraid it's not that simple. st/dri is used on Wayland as well, in
which case buffers passed to flush_resource aren't generally
displayable. See https://patchwork.freedesktop.org/patch/71713/ .


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer