linux-kernel - Re: [PATCH 6/7] drm/msm/A6XX: Add a flag to allow preemption to submitqueue

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Message-ID: <3c0ce811-ae61-4d09-8eb4-054afeaa1969@gmail.com>
Date: Fri, 23 Aug 2024 02:01:55 +0200
From: Antonino Maniscalco <antomani103@...il.com>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>,
 Connor Abbott <cwabbott0@...il.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] drm/msm/A6XX: Add a flag to allow preemption to
 submitqueue_create

On 8/22/24 9:21 PM, Akhil P Oommen wrote:
> On Tue, Aug 20, 2024 at 11:48:33AM +0100, Connor Abbott wrote:
>> On Mon, Aug 19, 2024 at 9:31 PM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>>>
>>> On Thu, Aug 15, 2024 at 08:26:16PM +0200, Antonino Maniscalco wrote:
>>>> Some userspace changes are necessary so add a flag for userspace to
>>>> advertise support for preemption.
>>>
>>> So the intention is to fallback to level 0 preemption until user moves
>>> to Mesa libs with level 1 support for each new GPU? Please elaborate a bit.
>>>
>>> -Akhil.
>>
>> Yes, that's right. My Mesa series fixes L1 preemption and
>> skipsaverestore by changing some of the CP_SET_MARKER calls and
>> register programming and introducing CP_SET_AMBLE calls and then
>> enables the flag on a7xx.
> 
> And we want to control L1 preemption per submitqueue because both
> freedreno and turnip may not have support ready at the same time?
> 
> Antonino, since this is a UAPI update, it is good to have these details
> captured in the commit msg for reference.
> 
> -Akhil.
> 

Sure I will update the commit message. Anyway that could be a valid 
reason but there is also nothing preventing you from loading different 
versions of mesa in two different processes so having one globally 
enable preemption and break it for the other wouldn't be ideal. It felt 
natural to have it per submitqueue.

Best regards,
-- 
Antonino Maniscalco <antomani103@...il.com>