linux-kernel - Re: [PATCH 08/17] drm/msm/a6xx: Set Keep-alive votes to block IFPC

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Message-ID: <vqncxeag7jqmtxmeezvwqdtneoavs5kazpcgweuw52knqbiukl@3iifyfkgkw52>
Date: Wed, 23 Jul 2025 14:13:00 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>
Cc: 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>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/17] drm/msm/a6xx: Set Keep-alive votes to block IFPC

On Wed, Jul 23, 2025 at 02:54:59AM +0530, Akhil P Oommen wrote:
> On 7/22/2025 7:14 PM, Dmitry Baryshkov wrote:
> > On Sun, Jul 20, 2025 at 05:46:09PM +0530, Akhil P Oommen wrote:
> >> Set Keepalive votes at appropriate places to block IFPC power collapse
> >> until we access all the required registers. This is required during gpu
> >> IRQ handling and also during preemption.
> >>
> >> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> >> ---
> >>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c     | 26 +++++++++++++++++---------
> >>  drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 20 ++++++++++++++++++++
> >>  2 files changed, 37 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> index 8c004fc3abd2896d467a9728b34e99e4ed944dc4..6770f0363e7284e4596b1188637a4615d2c0779b 100644
> >> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> @@ -1752,8 +1752,6 @@ static void a6xx_cp_hw_err_irq(struct msm_gpu *gpu)
> >>  
> >>  static void a6xx_fault_detect_irq(struct msm_gpu *gpu)
> >>  {
> >> -	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> >> -	struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> >>  	struct msm_ringbuffer *ring = gpu->funcs->active_ring(gpu);
> >>  
> >>  	/*
> >> @@ -1765,13 +1763,6 @@ static void a6xx_fault_detect_irq(struct msm_gpu *gpu)
> >>  	if (gpu_read(gpu, REG_A6XX_RBBM_STATUS3) & A6XX_RBBM_STATUS3_SMMU_STALLED_ON_FAULT)
> >>  		return;
> >>  
> >> -	/*
> >> -	 * Force the GPU to stay on until after we finish
> >> -	 * collecting information
> >> -	 */
> >> -	if (!adreno_has_gmu_wrapper(adreno_gpu))
> >> -		gmu_write(&a6xx_gpu->gmu, REG_A6XX_GMU_GMU_PWR_COL_KEEPALIVE, 1);
> >> -
> >>  	DRM_DEV_ERROR(&gpu->pdev->dev,
> >>  		"gpu fault ring %d fence %x status %8.8X rb %4.4x/%4.4x ib1 %16.16llX/%4.4x ib2 %16.16llX/%4.4x\n",
> >>  		ring ? ring->id : -1, ring ? ring->fctx->last_fence : 0,
> >> @@ -1810,9 +1801,24 @@ static void a7xx_sw_fuse_violation_irq(struct msm_gpu *gpu)
> >>  	}
> >>  }
> >>  
> >> +static void set_keepalive_vote(struct msm_gpu *gpu, bool on)
> > 
> > a6xx_set_keepalive_vote()
> 
> static fn! Why do we need prefix here?

It's really a good custom. Also, note that I suggested two different
names to your functions (otherwise it's too easy to get confused).

> >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> >> index 5b0fd510ff58d989ab285f1a2497f6f522a6b187..1c8ec1911010c00a000d195116fc950c4d947cac 100644
> >> --- a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> >> @@ -136,6 +136,21 @@ static void preempt_disable_postamble(struct a6xx_gpu *a6xx_gpu)
> >>  	a6xx_gpu->postamble_enabled = false;
> >>  }
> >>  
> >> +/*
> >> + * Set preemption keepalive vote. Please note that this vote is different from the one used in
> >> + * a6xx_irq()
> >> + */
> >> +static void set_keepalive_vote(struct msm_gpu *gpu, bool on)
> > 
> > a6xx_set_preempt_keepalive_vote();
> > 

-- 
With best wishes
Dmitry