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

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Message-ID: <f7b637d6-6afc-4102-aabd-aded710bd87f@quicinc.com>
Date: Wed, 22 Jan 2025 19:45:49 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>
CC: 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 1/17/2025 2:46 AM, Konrad Dybcio wrote:
> 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"..

Sounds good. I can explore that when I am back from vacation early next
month.

-Akhil.

> 
> Konrad