[PATCH v3] drm/amdgpu: add workarounds for VCN TMZ issue on CHIP_RAVEN

[Christian König]

Am 16.03.22 um 10:57 schrieb Paul Menzel:
> Dear Christian,
>
>
> Am 16.03.22 um 10:41 schrieb Christian König:
>> Am 16.03.22 um 07:21 schrieb Lang Yu:
>>> On 03/16/ , Paul Menzel wrote:
>
>>>> Am 16.03.22 um 02:27 schrieb Lang Yu:
>>>>> On 03/15/ , Paul Menzel wrote:
>>>>>> Am 14.03.22 um 03:45 schrieb Lang Yu:
>>>>>>
>>>>>> Thank you for your patch. A shorter commit message summary would be:
>>>>>>
>>>>>>> drm/amdgpu: Work around VNC TMZ issue on CHIP_RAVEN
>>>>>>> It is a hardware issue that VCN can't handle a GTT
>>>>>>> backing stored TMZ buffer on CHIP_RAVEN series ASIC.
>>>>>> Where is that documented, and how can this be reproduced?
>>>>> It is documented in AMD internal Confluence and JIRA.
>>>>> Secure playback with a low VRAM config(thus TMZ buffer
>>>>> will be allocted in GTT domain) may reproduce this issue.
>>>> It’d be great if as much of the details from this non-publicly 
>>>> accessible
>>>> information could be added to the commit message, and a way to 
>>>> reproduce
>>>> this as there does not seem to be a test for this. (Also I guess a 
>>>> tag with
>>>> a reference to the internal issue would be acceptable, so in case more
>>>> question surface in the future.)
>>> Thanks. I will add an internal link.
>>
>> Lang, please don't!
>>
>> This isn't an information which is expected to be made public.
>
> Well, how are then even the AMD folks able to link a (upstream) commit 
> to an issue?

Well quite simply: We don't do that since it isn't necessary.

>
> If it’s not possible, even more detailed information about the issue 
> including how to reproduce it needs to be part of the commit message.

No, why should we do that? It's an AMD internal hardware problem which 
we add a software workaround for here. The hardware details why and what 
are completely irrelevant to the public.

All that we need to document is that VCN can't handle GTT on Raven, and 
that's exactly what the commit message is doing. That's perfectly enough 
to write a test case.

Regards,
Christian.

>
>
> Kind regards,
>
> Paul
>
>
> PS: The coreboot project includes references to Google’s internal 
> bug/issue tracker, but also has the requirement that the commit can be 
> reviewed and tested without access to it.