linux-kernel - Re: [PATCH v2 02/21] drm/msm/a6xx: Fix the gemnoc workaround

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Message-ID: <a1273bdf-d926-48b4-877e-48d5ff45e7d9@oss.qualcomm.com>
Date: Wed, 12 Nov 2025 11:18:04 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Sean Paul <sean@...rly.run>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar
 <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse
 <jordan@...micpenguin.net>,
        Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Connor Abbott <cwabbott0@...il.com>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 02/21] drm/msm/a6xx: Fix the gemnoc workaround

On 11/10/25 5:37 PM, Akhil P Oommen wrote:
> Correct the register offset and enable this workaround for all A7x
> and newer GPUs to match the recommendation. Also, downstream does this
> w/a after moving the fence to allow mode. So do the same.

It does so for _notify_slumber(), but not for _pwrctl_suspend() in kgsl,
but in my understanding, making sure the bus arbiter doesn't gate access
first makes more sense

> 
> Fixes: dbfbb376b50c ("drm/msm/a6xx: Add A621 support")
> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index 4e6dc16e4a4c..605bb55de8d5 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -485,8 +485,9 @@ static void a6xx_gemnoc_workaround(struct a6xx_gmu *gmu)
>  	 * in the power down sequence not being fully executed. That in turn can
>  	 * prevent CX_GDSC from collapsing. Assert Qactive to avoid this.
>  	 */
> -	if (adreno_is_a621(adreno_gpu) || adreno_is_7c3(adreno_gpu))
> -		gmu_write(gmu, REG_A6XX_GMU_AO_AHB_FENCE_CTRL, BIT(0));
> +	if (adreno_is_a7xx(adreno_gpu) || (adreno_is_a621(adreno_gpu) ||
> +				adreno_is_7c3(adreno_gpu)))
> +		gmu_write(gmu, REG_A6XX_GPU_GMU_CX_GMU_CX_FALNEXT_INTF, BIT(0));

Arghhh copypasta, thanks for catching this!

Konrad