Re: [PATCH] drm/msm: Fix removal of valid error case when checking speed_bin

[Akhil P Oommen]

On 3/30/2021 7:04 AM, John Stultz wrote:
> Commit 7bf168c8fe8c  ("drm/msm: Fix speed-bin support not to
> access outside valid memory"), reworked the nvmem reading of
> "speed_bin", but in doing so dropped handling of the -ENOENT
> case which was previously documented as "fine".
>
> That change resulted in the db845c board display to fail to
> start, with the following error:
>
> adreno 5000000.gpu: [drm:a6xx_gpu_init] *ERROR* failed to read speed-bin (-2). Some OPPs may not be supported by hardware
>
> Thus, this patch simply re-adds the ENOENT handling so the lack
> of the speed_bin entry isn't fatal for display, and gets things
> working on db845c.
>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Cc: Sean Paul <sean@xxxxxxxxxx>
> Cc: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> Cc: Eric Anholt <eric@xxxxxxxxxx>
> Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
> Cc: linux-arm-msm@xxxxxxxxxxxxxxx
> Cc: freedreno@xxxxxxxxxxxxxxxxxxxxx
> Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> Cc: YongQin Liu <yongqin.liu@xxxxxxxxxx>
> Reported-by: YongQin Liu <yongqin.liu@xxxxxxxxxx>
> Fixes: 7bf168c8fe8c  ("drm/msm: Fix speed-bin support not to access outside valid memory")
> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> ---
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 690409ca8a186..cb2df8736ca85 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1406,7 +1406,13 @@ static int a6xx_set_supported_hw(struct device *dev, struct a6xx_gpu *a6xx_gpu,
>   	int ret;
>   
>   	ret = nvmem_cell_read_u16(dev, "speed_bin", &speedbin);
> -	if (ret) {
> +	/*
> +	 * -ENOENT means that the platform doesn't support speedbin which is
> +	 * fine
> +	 */
> +	if (ret == -ENOENT) {
> +		return 0;
> +	} else if (ret) {
>   		DRM_DEV_ERROR(dev,
>   			      "failed to read speed-bin (%d). Some OPPs may not be supported by hardware",
>   			      ret);

Reviewed-by: Akhil P Oommen <akhilpo@xxxxxxxxxxxxxx>

This looks "fine" to me. ;)

-Akhil.