linux-kernel - Re: [PATCH RFT v6 2/5] drm/msm/adreno: Add speedbin data for SM8550 / A740

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Message-ID: <a26213ec-808f-4edf-bb0d-ab469ee0a884@linaro.org>
Date: Wed, 30 Apr 2025 16:49:17 +0200
From: neil.armstrong@...aro.org
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Konrad Dybcio <konradybcio@...nel.org>, Rob Clark <robdclark@...il.com>,
 Sean Paul <sean@...rly.run>, Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Dmitry Baryshkov <lumag@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Bjorn Andersson <andersson@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
 linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: Re: [PATCH RFT v6 2/5] drm/msm/adreno: Add speedbin data for SM8550 /
 A740

On 30/04/2025 15:09, Konrad Dybcio wrote:
> On 4/30/25 2:49 PM, neil.armstrong@...aro.org wrote:
>> On 30/04/2025 14:35, Konrad Dybcio wrote:
>>> On 4/30/25 2:26 PM, neil.armstrong@...aro.org wrote:
>>>> Hi,
>>>>
>>>> On 30/04/2025 13:34, Konrad Dybcio wrote:
>>>>> From: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>>>
>>>>> Add speebin data for A740, as found on SM8550 and derivative SoCs.
>>>>>
>>>>> For non-development SoCs it seems that "everything except FC_AC, FC_AF
>>>>> should be speedbin 1", but what the values are for said "everything" are
>>>>> not known, so that's an exercise left to the user..
>>>>>
>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>>> ---
>>>>>     drivers/gpu/drm/msm/adreno/a6xx_catalog.c | 8 ++++++++
>>>>>     1 file changed, 8 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>>> index 53e2ff4406d8f0afe474aaafbf0e459ef8f4577d..61daa331567925e529deae5e25d6fb63a8ba8375 100644
>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>>> @@ -11,6 +11,9 @@
>>>>>     #include "a6xx.xml.h"
>>>>>     #include "a6xx_gmu.xml.h"
>>>>>     +#include <linux/soc/qcom/smem.h>
>>>>> +#include <linux/soc/qcom/socinfo.h>
>>>>> +
>>>>>     static const struct adreno_reglist a612_hwcg[] = {
>>>>>         {REG_A6XX_RBBM_CLOCK_CNTL_SP0, 0x22222222},
>>>>>         {REG_A6XX_RBBM_CLOCK_CNTL2_SP0, 0x02222220},
>>>>> @@ -1431,6 +1434,11 @@ static const struct adreno_info a7xx_gpus[] = {
>>>>>             },
>>>>>             .address_space_size = SZ_16G,
>>>>>             .preempt_record_size = 4192 * SZ_1K,
>>>>> +        .speedbins = ADRENO_SPEEDBINS(
>>>>> +            { ADRENO_SKU_ID(SOCINFO_FC_AC), 0 },
>>>>> +            { ADRENO_SKU_ID(SOCINFO_FC_AF), 0 },
>>>>> +            /* Other feature codes (on prod SoCs) should match to speedbin 1 */
>>>>
>>>> I'm trying to understand this sentence. because reading patch 4, when there's no match
>>>> devm_pm_opp_set_supported_hw() is simply never called so how can it match speedbin 1 ?
>>>
>>> What I'm saying is that all other entries that happen to be possibly
>>> added down the line are expected to be speedbin 1 (i.e. BIT(1))
>>>
>>>> Before this change the fallback was speedbin = BIT(0), but this disappeared.
>>>
>>> No, the default was to allow speedbin mask ~(0U)
>>
>> Hmm no:
>>
>>      supp_hw = fuse_to_supp_hw(info, speedbin);
>>
>>      if (supp_hw == UINT_MAX) {
>>          DRM_DEV_ERROR(dev,
>>              "missing support for speed-bin: %u. Some OPPs may not be supported by hardware\n",
>>              speedbin);
>>          supp_hw = BIT(0); /* Default */
>>      }
>>
>>      ret = devm_pm_opp_set_supported_hw(dev, &supp_hw, 1);
>>      if (ret)
>>          return ret;
> 
> Right, that's my own code even..
> 
> in any case, the kernel can't know about the speed bins that aren't
> defined and here we only define bin0, which doesn't break things
> 
> the kernel isn't aware about hw with bin1 with or without this change
> so it effectively doesn't matter

But it's regression for the other platforms, where before an unknown SKU
mapped to supp_hw=BIT(0)

Not calling devm_pm_opp_set_supported_hw() is a major regression,
if the opp-supported-hw is present, the OPP will be rejected:

https://elixir.bootlin.com/linux/v6.14.4/source/drivers/opp/of.c#L538

	if (!opp_table->supported_hw) {
		/*
		 * In the case that no supported_hw has been set by the
		 * platform but there is an opp-supported-hw value set for
		 * an OPP then the OPP should not be enabled as there is
		 * no way to see if the hardware supports it.
		 */
		if (of_property_present(np, "opp-supported-hw"))
			return false;
		else
			return true;
	}

Neil

> 
> Konrad