linux-kernel - Re: [PATCH 15/17] drm/msm/a6xx: Make crashstate capture IFPC safe

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Message-ID: <343d2e49-aa52-463b-a844-e78af2a54d1d@oss.qualcomm.com>
Date: Thu, 24 Jul 2025 03:23:57 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/17] drm/msm/a6xx: Make crashstate capture IFPC safe

On 7/23/2025 4:02 PM, Konrad Dybcio wrote:
> On 7/20/25 2:16 PM, Akhil P Oommen wrote:
>> Now with IFPC, GX domain can collapse as soon as GPU becomes IDLE. So
>> add gx_is_on check before accessing any GX registers during crashstate
>> capture and recovery.
>>
>> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
>> ---
> 
> [...]
> 
>> +	/*
>> +	 * This is true only on an A6XX_GEN1 with GMU, has IFPC enabled and a super old SQE firmware
>> +	 * without 'whereami' support
>> +	 */
> 
> Firmware that old won't even be accepted by the driver, see the slightly
> confusing logic in a6xx_ucode_check_version()

hmm. you are right. In that case, I don't know why we still have the
below bit here:

	ring->memptrs->rptr = gpu_read(gpu, REG_A6XX_CP_RB_RPTR);

-Akhil

> 
> Konrad