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

[Deng, Emily]

>-----Original Message-----
>From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Deng,
>Emily
>Sent: Friday, December 21, 2018 5:10 PM
>To: Michel Dänzer <michel at daenzer.net>
>Cc: amd-gfx at lists.freedesktop.org
>Subject: RE: [PATCH] drm/amdgpu/virtual_dce: Need to pin the fb's bo
>
>>-----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.
It seems to be hard to remove all the pin for virtual_dce, as it uses some common code in amdgpu_display.c.
So for code consistency, maybe still need to add the pin here.

Best wishes
Emily Deng
>>
>>
>>--
>>Earthling Michel Dänzer               |               http://www.amd.com
>>Libre software enthusiast             |             Mesa and X developer
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