linux-kernel - Re: [PATCH RFC 1/4] drm/msm/adreno: Add speedbin support for X1-85

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Message-ID: <404e8b7d-30ef-47f2-8a44-927b201d60ec@oss.qualcomm.com>
Date: Thu, 16 Jan 2025 22:16:25 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.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
Subject: Re: [PATCH RFC 1/4] drm/msm/adreno: Add speedbin support for X1-85

On 15.01.2025 8:59 PM, Dmitry Baryshkov wrote:
> On Thu, Jan 16, 2025 at 01:07:17AM +0530, Akhil P Oommen wrote:
>> On 1/9/2025 7:27 PM, Konrad Dybcio wrote:
>>> On 8.01.2025 11:42 PM, Akhil P Oommen wrote:
>>>> Adreno X1-85 has an additional bit which is at a non-contiguous
>>>> location in qfprom. Add support for this new "hi" bit along with
>>>> the speedbin mappings.
>>>> ---
>>>>  drivers/gpu/drm/msm/adreno/a6xx_catalog.c |  5 +++++
>>>>  drivers/gpu/drm/msm/adreno/adreno_gpu.c   | 15 ++++++++++++++-
>>>>  2 files changed, 19 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>> index 0c560e84ad5a53bb4e8a49ba4e153ce9cf33f7ae..e2261f50aabc6a2f931d810f3637dfdba5695f43 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>> @@ -1412,6 +1412,11 @@ static const struct adreno_info a7xx_gpus[] = {
>>>>  			.gmu_cgc_mode = 0x00020202,
>>>>  		},
>>>>  		.address_space_size = SZ_256G,
>>>> +		.speedbins = ADRENO_SPEEDBINS(
>>>> +			{ 0,   0 },
>>>> +			{ 263, 1 },
>>>> +			{ 315, 0 },
>>>> +		),
>>>>  		.preempt_record_size = 4192 * SZ_1K,
>>>>  	}, {
>>>>  		.chip_ids = ADRENO_CHIP_IDS(0x43051401), /* "C520v2" */
>>>> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> index 75f5367e73caace4648491b041f80b7c4d26bf89..7b31379eff444cf3f8ed0dcfd23c14920c13ee9d 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> @@ -1078,7 +1078,20 @@ void adreno_gpu_ocmem_cleanup(struct adreno_ocmem *adreno_ocmem)
>>>>  
>>>>  int adreno_read_speedbin(struct device *dev, u32 *speedbin)
>>>>  {
>>>> -	return nvmem_cell_read_variable_le_u32(dev, "speed_bin", speedbin);
>>>> +	u32 hi_bits = 0;
>>>> +	int ret;
>>>> +
>>>> +	ret = nvmem_cell_read_variable_le_u32(dev, "speed_bin", speedbin);
>>>> +	if (ret)
>>>> +		return ret;
>>>> +
>>>> +	/* Some chipsets have MSB bits (BIT(8) and above) at a non-contiguous location */
>>>> +	ret = nvmem_cell_read_variable_le_u32(dev, "speed_bin_hi", &hi_bits);
>>>> +	if (ret != -ENOENT)
>>>> +		return ret;
>>>> +
>>>> +	*speedbin |= (hi_bits << 8);
>>>
>>> Now that we're overwriting speedbin, we should probably have some checks in
>>> order to make sure somebody passing a too-wide cell to one of these won't
>>> result in cripplingly-untraceable value corruption
>>>
>>> I guess we could just introduce nvmem_cell_read_variable_le_u8() and call it
>>> a day?
>>
>> X1E is an outlier here, because this was fixed from the next chipset
>> onward. For newer chipsets, we can use just the "speed_bin" node, which
>> represents a contiguous 9 bits. So, just do a "WARN_ON(fls(speedbin) >
>> 8)" here?
> 
> Or extend nvmem core to support non-contiguous fields.

This sounds more desirable, as we surely aren't the only ones with
such a "feature"..

Konrad