[PATCH v2 1/3] drm/msm/adreno: Add support for ACD

[Akhil P Oommen]

On 10/22/2024 2:37 PM, Bryan O'Donoghue wrote:
> On 21/10/2024 12:53, Akhil P Oommen wrote:
>> ACD a.k.a Adaptive Clock Distribution is a feature which helps to reduce
>> the power consumption. In some chipsets, it is also a requirement to
>> support higher GPU frequencies. This patch adds support for GPU ACD by
>> sending necessary data to GMU and AOSS. The feature support for the
>> chipset is detected based on devicetree data.
>>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo at quicinc.com>
>> ---
>>   drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 81 ++++++++++++++++++++++++++++-------
>>   drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  1 +
>>   drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 36 ++++++++++++++++
>>   drivers/gpu/drm/msm/adreno/a6xx_hfi.h | 21 +++++++++
>>   4 files changed, 124 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> index 37927bdd6fbe..09fb3f397dbb 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> @@ -1021,14 +1021,6 @@ int a6xx_gmu_resume(struct a6xx_gpu *a6xx_gpu)
>>         gmu->hung = false;
>>   -    /* Notify AOSS about the ACD state (unimplemented for now => disable it) */
>> -    if (!IS_ERR(gmu->qmp)) {
>> -        ret = qmp_send(gmu->qmp, "{class: gpu, res: acd, val: %d}",
>> -                   0 /* Hardcode ACD to be disabled for now */);
>> -        if (ret)
>> -            dev_err(gmu->dev, "failed to send GPU ACD state\n");
>> -    }
>> -
>>       /* Turn on the resources */
>>       pm_runtime_get_sync(gmu->dev);
>>   @@ -1476,6 +1468,64 @@ static int a6xx_gmu_pwrlevels_probe(struct a6xx_gmu *gmu)
>>       return a6xx_gmu_rpmh_votes_init(gmu);
>>   }
>>   +static int a6xx_gmu_acd_probe(struct a6xx_gmu *gmu)
>> +{
>> +    struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
>> +    struct a6xx_hfi_acd_table *cmd = &gmu->acd_table;
>> +    struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
>> +    struct msm_gpu *gpu = &adreno_gpu->base;
>> +    int ret, i, cmd_idx = 0;
>> +
>> +    cmd->version = 1;
>> +    cmd->stride = 1;
>> +    cmd->enable_by_level = 0;
>> +
>> +    /* Skip freq = 0 and parse acd-level for rest of the OPPs */
>> +    for (i = 1; i < gmu->nr_gpu_freqs; i++) {
>> +        struct dev_pm_opp *opp;
>> +        struct device_node *np;
>> +        unsigned long freq;
>> +        u32 val;
>> +
>> +        freq = gmu->gpu_freqs[i];
>> +        opp = dev_pm_opp_find_freq_exact(&gpu->pdev->dev, freq, true);
>> +        np = dev_pm_opp_get_of_node(opp);
>> +
>> +        ret = of_property_read_u32(np, "qcom,opp-acd-level", &val);
>> +        of_node_put(np);
>> +        dev_pm_opp_put(opp);
>> +        if (ret == -EINVAL)
>> +            continue;
>> +        else if (ret) {
>> +            DRM_DEV_ERROR(gmu->dev, "Unable to read acd level for freq %lu\n", freq);
>> +            return ret;
>> +        }
>> +
>> +        cmd->enable_by_level |= BIT(i);
>> +        cmd->data[cmd_idx++] = val;
> 
> How do you know that cmd_idx is always < sizeof(cmd->data); ?

Because "i < nr_gpu_freqs".

I can think of some potential improvements here, but that is outside
the scope of this patch.

> 
>> +    }
>> +
>> +    cmd->num_levels = cmd_idx;
>> +
>> +    /* We are done here if ACD is not required for any of the OPPs */
>> +    if (!cmd->enable_by_level)
>> +        return 0;
>> +
>> +    /* Initialize qmp node to talk to AOSS */
>> +    gmu->qmp = qmp_get(gmu->dev);
>> +    if (IS_ERR(gmu->qmp)) {
>> +        cmd->enable_by_level = 0;
>> +        return dev_err_probe(gmu->dev, PTR_ERR(gmu->qmp), "Failed to initialize qmp\n");
>> +    }
>> +
>> +    /* Notify AOSS about the ACD state */
>> +    ret = qmp_send(gmu->qmp, "{class: gpu, res: acd, val: %d}", 1);
>> +    if (ret)
>> +        DRM_DEV_ERROR(gmu->dev, "failed to send GPU ACD state\n");
>> +
>> +    return 0;
> 
> Shouldn't the ret from gmp_send() get propogated in the return of this function ?
> 
> i.e. how can your probe be successful if the notification failed ?

Failure to send this message to AOP is not worth failing the
probe. We just loose a little bit of power savings.

-Akhil.

> 
> ---
> bod