linux-kernel - Re: [PATCH 13/14] drm/msm/a6xx: Add A619

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Message-ID: <c8d9d5f0-dab8-4dca-5a32-1f4e11ecc964@linaro.org>
Date:   Fri, 27 Jan 2023 16:19:42 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org, krzysztof.kozlowski@...aro.org
Cc:     marijn.suijten@...ainline.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Chia-I Wu <olvaffe@...il.com>,
        Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/14] drm/msm/a6xx: Add A619_holi speedbin support

On 26/01/2023 17:16, Konrad Dybcio wrote:
> A619_holi is implemented on at least two SoCs: SM4350 (holi) and SM6375
> (blair). This is what seems to be a first occurrence of this happening,
> but it's easy to overcome by guarding the SoC-specific fuse values with
> of_machine_is_compatible(). Do just that to enable frequency limiting
> on these SoCs.
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 31 +++++++++++++++++++++++++++
>   1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 452ba32699b2..89990bec897f 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -2091,6 +2091,34 @@ static u32 a618_get_speed_bin(u32 fuse)
>   	return UINT_MAX;
>   }
>   
> +static u32 a619_holi_get_speed_bin(u32 fuse)
> +{
> +	/*
> +	 * There are (at least) two SoCs implementing A619_holi: SM4350 (holi)
> +	 * and SM6375 (blair). Limit the fuse matching to the corresponding
> +	 * SoC to prevent bogus frequency setting (as improbable as it may be,
> +	 * given unexpected fuse values are.. unexpected! But still possible.)
> +	 */
> +
> +	if (fuse == 0)
> +		return 0;
> +
> +	if (of_machine_is_compatible("qcom,sm4350")) {
> +		if (fuse == 138)
> +			return 1;
> +		else if (fuse == 92)
> +			return 2;
> +	} else if (of_machine_is_compatible("qcom,sm6375")) {
> +		if (fuse == 190)
> +			return 1;
> +		else if (fuse == 177)
> +			return 2;
> +	} else
> +		pr_warn("Unknown SoC implementing A619_holi!\n");

I think, we might be better to introduce "qcom,SoC-adreno" compat string 
instead, ignore it in the bindings and only care about it here. This 
might seem an overkill thinking from the single Adreno version. However 
this issue also affects other revisions.

For example, for the A618 there are at least three platforms which use 
the same Adreno version: SC7180, SM7125 and SM7150. Only first one is 
supported (thus the speed_bin function is simple). However according to 
the vendor dts files all three platforms use different fuse values to 
specify the speed bin.

> +
> +	return UINT_MAX;
> +}
> +
>   static u32 a619_get_speed_bin(u32 fuse)
>   {
>   	if (fuse == 0)
> @@ -2150,6 +2178,9 @@ static u32 fuse_to_supp_hw(struct device *dev, struct adreno_rev rev, u32 fuse)
>   	if (adreno_cmp_rev(ADRENO_REV(6, 1, 8, ANY_ID), rev))
>   		val = a618_get_speed_bin(fuse);
>   
> +	else if (adreno_cmp_rev(ADRENO_REV(6, 1, 9, 1), rev))
> +		val = a619_holi_get_speed_bin(fuse);
> +

Are we sure that SM6350, the unholi A619 user, doesn't use patchid .1? 
(note I do not know a thing about Adreno patch ids and its usage between 
different platforms).

>   	else if (adreno_cmp_rev(ADRENO_REV(6, 1, 9, ANY_ID), rev))
>   		val = a619_get_speed_bin(fuse);
>   

-- 
With best wishes
Dmitry