linux-kernel - Re: [PATCH v8 08/18] drm/msm/a6xx: Remove both GBIF and RBBM GBIF halt on hw init

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Date:   Fri, 9 Jun 2023 23:55:29 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
CC:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Conor Dooley <conor+dt@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Rob Clark <robdclark@...omium.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>
Subject: Re: [PATCH v8 08/18] drm/msm/a6xx: Remove both GBIF and RBBM GBIF
 halt on hw init

On Mon, May 29, 2023 at 03:52:27PM +0200, Konrad Dybcio wrote:
> 
> Currently we're only deasserting REG_A6XX_RBBM_GBIF_HALT, but we also
> need REG_A6XX_GBIF_HALT to be set to 0.
> 
> This is typically done automatically on successful GX collapse, but in
> case that fails, we should take care of it.
> 
> Also, add a memory barrier to ensure it's gone through before jumping
> to further initialization.
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 083ccb5bcb4e..dfde5fb65eed 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1003,8 +1003,12 @@ static int hw_init(struct msm_gpu *gpu)
>  	a6xx_gmu_set_oob(&a6xx_gpu->gmu, GMU_OOB_GPU_SET);
>  
>  	/* Clear GBIF halt in case GX domain was not collapsed */
> -	if (a6xx_has_gbif(adreno_gpu))
> +	if (a6xx_has_gbif(adreno_gpu)) {
> +		gpu_write(gpu, REG_A6XX_GBIF_HALT, 0);
>  		gpu_write(gpu, REG_A6XX_RBBM_GBIF_HALT, 0);
> +		/* Let's make extra sure that the GPU can access the memory.. */
> +		mb();
This barrier is unnecessary because writel transactions are ordered and
we don't expect a traffic from GPU immediately after this.

-Akhil
> +	}
>  
>  	gpu_write(gpu, REG_A6XX_RBBM_SECVID_TSB_CNTL, 0);
>  
> 
> -- 
> 2.40.1
>