[PATCH] drm/amdgpu: fix the ib test hang when gfx is in "idle" state

[Alex Deucher]

On Mon, Apr 23, 2018 at 8:13 AM, Huang Rui <ray.huang at amd.com> wrote:
> On Mon, Apr 23, 2018 at 05:57:06PM +0800, Koenig, Christian wrote:
>> Hi Ray,
>>
>> Am 23.04.2018 11:47 schrieb Huang Rui <ray.huang at amd.com>:
>>
>>     On Fri, Apr 20, 2018 at 05:59:16PM +0800, Koenig, Christian wrote:
>>     > Am 20.04.2018 um 11:40 schrieb Huang Rui:
>>     > > "aaabaf4   drm/amdgpu: defer test IBs on the rings at boot (V3)"
>>     > > Above patch defers the execution of gfx/compute ib tests. However, at
>>     that time,
>>     > > the gfx may already go into idle state. If "idle" gfx receives command
>>     > > submission, it will get hang in the system. So we must add is_gfx_on
>>     checking at
>>     > > start of ib tests.
>>     >
>>     > Do I see that right that you just skip the IB test when the GFX block is
>>     > already turned of? In this case that would be a clear NAK.
>>     >
>>     > BTW: How do you detect that we need to turn GFX on again?
>>
>>     Christian, I know point. But there is a hang issue if we would like try to
>>     disable/enable gfxoff with SMC message at runtime. Actually, I am trying to
>>     find a good sequence to fix it. After that, I can even expose an debugfs
>>     interface to configure that. So I have to skip the test for the moment when
>>     gfx is in "idle".
>>
>>
>> Working around that issue for the moment is ok, but please note that explicitly
>> in both the commit message and a code comment.
>
> OK. Will add it at V2.
>
>>
>> But don't you run into the same problem when the UMD starts to submit commands?
>
> When UMD starts, RLC firmware will detect the "draw" command, then it will
> power up gfx. So it won't have problem at that time. The mainly state
> machine doesn't expose to driver side yet.
>
>>
>> I mean the idea of the IB test is that you "simulate" an userspace command
>> submission and see if it works.
>>
>
> Yes, agree. Any idea to "simulate" the "draw" command? Or please wait for
> my fix for enabling/disabling gfxoff at runtime.


Is there some special formatting in the IB required?  I don't really
see how this will work.  There is likely tons of state before the
actual draw command in the IB.

Alex

>
> Thanks,
> Ray
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