[PATCH 3/3] drm/amdgpu/vcn: Add parameter to force (en/dis)abling indirect SRAM mode

[Limonciello, Mario]

On 1/16/2023 18:47, Guilherme G. Piccoli wrote:
> On 16/01/2023 20:00, Alex Deucher wrote:
>> [...]
>>
>> It's not clear to me when this would be used.  We only disable it
>> briefly during new asic bring up, after that we never touch it again.
>> No end user on production hardware should ever have to change it and
>> doing so would break VCN on their system.
>>
>> Alex
> 
> [+ Pierre-Loup]
> 
> Steam Deck is facing a pretty weird scenario then heheh
> 
> Commit 82132ecc543 ("drm/amdgpu: enable Vangogh VCN indirect sram mode")
> corrected a long-term issue in which the indirect SRAM mode wasn't
> enabled for Vangogh - and Deck GPU architecture is Vangogh, so it was
> working perfectly with that disabled.
> 
> Happens that a bad FW candidate seems to have broken something - it was
> a bit convoluted to debug, but we proved that disabling indirect SRAM is
> a good workaround so far, it "restored the behavior" pre-82132ecc543.
> 
> Hence my proposal - this parameter would've made life so much easier,
> and we're start using it "downstream" now. While I understand that of
> course the FW should be fixed, meanwhile this is a cheap solution to
> allow further debug and real use of the system.
> 

For debugging these type of problems, I think an effective debugging 
tactic would have been to mask the IP block (amdgpu.ip_block_mask).