[PATCH] drm/amdgpu/virtual_dce: Need to pin the fb's bo

[Deng, Emily]

>-----Original Message-----
>From: Michel Dänzer <michel at daenzer.net>
>Sent: Friday, December 21, 2018 4:52 PM
>To: Deng, Emily <Emily.Deng at amd.com>
>Cc: amd-gfx at lists.freedesktop.org
>Subject: Re: [PATCH] drm/amdgpu/virtual_dce: Need to pin the fb's bo
>
>On 2018-12-21 9:45 a.m., Deng, Emily wrote:
>>> -----Original Message-----
>>> From: Michel Dänzer <michel at daenzer.net>
>>> Sent: Friday, December 21, 2018 4:38 PM
>>> To: Deng, Emily <Emily.Deng at amd.com>
>>> Cc: amd-gfx at lists.freedesktop.org
>>> Subject: Re: [PATCH] drm/amdgpu/virtual_dce: Need to pin the fb's bo
>>>
>>> On 2018-12-21 8:26 a.m., Emily Deng wrote:
>>>> When the bo is used to set mode, the bo need to be pinned.
>>>
>>> On second thought, why does the BO need to be pinned? When using the
>>> display hardware, the BO needs to be pinned to prevent it from being
>>> moved while the hardware is scanning out from it, but that shouldn't be
>necessary here.
>> The pin here is used for scan out the buffer by remote display app.
>
>I still don't understand why pinning is needed. What mechanism does the remote
>display app use to access the BO contents?
Sorry, I am not familiar with the remote display app. Maybe it will use drm ioctl function to get the 
current crtc's fb's information, and get the content in the fb's buffer object by mmap or translate the bo
to an OpenGL texture for next rendering. Maybe don't need to pin the bo here, as the use has no different with
other normal bos. So please ignore the patch, and will send another patch to remove the unpin the fb's bo code. 
>
>
>--
>Earthling Michel Dänzer               |               http://www.amd.com
>Libre software enthusiast             |             Mesa and X developer