Re: [PATCH 1/5] drm/msm/adreno: Use OPP for every GPU generation

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 23.02.2023 00:16, Dmitry Baryshkov wrote:
> On 23/02/2023 00:40, Konrad Dybcio wrote:
>>
>>
>> On 22.02.2023 23:38, Dmitry Baryshkov wrote:
>>> On 22/02/2023 23:47, Konrad Dybcio wrote:
>>>> Some older GPUs (namely a2xx with no opp tables at all and a320 with
>>>> downstream-remnants gpu pwrlevels) used not to have OPP tables. They
>>>> both however had just one frequency defined, making it extremely easy
>>>> to construct such an OPP table from within the driver if need be.
>>>>
>>>> Do so and switch all clk_set_rate calls on core_clk to their OPP
>>>> counterparts.
>>>>
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>> ---
>>>>    drivers/gpu/drm/msm/adreno/adreno_gpu.c | 94 +++++++++++++++------------------
>>>>    drivers/gpu/drm/msm/msm_gpu.c           |  4 +-
>>>>    drivers/gpu/drm/msm/msm_gpu_devfreq.c   |  2 +-
>>>>    3 files changed, 45 insertions(+), 55 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> index ce6b76c45b6f..9b940c0f063f 100644
>>>> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
>>>> @@ -922,73 +922,50 @@ void adreno_wait_ring(struct msm_ringbuffer *ring, uint32_t ndwords)
>>>>                ring->id);
>>>>    }
>>>>    -/* Get legacy powerlevels from qcom,gpu-pwrlevels and populate the opp table */
>>>> -static int adreno_get_legacy_pwrlevels(struct device *dev)
>>>> -{
>>>> -    struct device_node *child, *node;
>>>> -    int ret;
>>>> -
>>>> -    node = of_get_compatible_child(dev->of_node, "qcom,gpu-pwrlevels");
>>>> -    if (!node) {
>>>> -        DRM_DEV_DEBUG(dev, "Could not find the GPU powerlevels\n");
>>>> -        return -ENXIO;
>>>> -    }
>>>> -
>>>> -    for_each_child_of_node(node, child) {
>>>> -        unsigned int val;
>>>> -
>>>> -        ret = of_property_read_u32(child, "qcom,gpu-freq", &val);
>>>> -        if (ret)
>>>> -            continue;
>>>> -
>>>> -        /*
>>>> -         * Skip the intentionally bogus clock value found at the bottom
>>>> -         * of most legacy frequency tables
>>>> -         */
>>>> -        if (val != 27000000)
>>>> -            dev_pm_opp_add(dev, val, 0);
>>>> -    }
>>>> -
>>>> -    of_node_put(node);
>>>> -
>>>> -    return 0;
>>>> -}
>>>> -
>>>> -static void adreno_get_pwrlevels(struct device *dev,
>>>> +static int adreno_get_pwrlevels(struct device *dev,
>>>>            struct msm_gpu *gpu)
>>>>    {
>>>> +    struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>>>>        unsigned long freq = ULONG_MAX;
>>>>        struct dev_pm_opp *opp;
>>>>        int ret;
>>>>          gpu->fast_rate = 0;
>>>>    -    /* You down with OPP? */
>>>> -    if (!of_find_property(dev->of_node, "operating-points-v2", NULL))
>>>> -        ret = adreno_get_legacy_pwrlevels(dev);
>>>> -    else {
>>>> -        ret = devm_pm_opp_of_add_table(dev);
>>>> -        if (ret)
>>>> -            DRM_DEV_ERROR(dev, "Unable to set the OPP table\n");
>>>> -    }
>>>> -
>>>> -    if (!ret) {
>>>> +    /* devm_pm_opp_of_add_table may error out but will still create an OPP table */
>>>> +    ret = devm_pm_opp_of_add_table(dev);
>>>> +    if (ret == -ENODEV) {
>>>> +        /* Special cases for ancient hw with ancient DT bindings */
>>>> +        if (adreno_is_a2xx(adreno_gpu)) {
>>>> +            dev_warn(dev, "Unable to find the OPP table. Falling back to 200 MHz.\n");
>>>> +            dev_pm_opp_add(dev, 200000000, 0);
>>>> +            gpu->fast_rate = 200000000;
>>>
>>> We can skip setting the fast_rate, dev_pm_opp_find_freq_floor below will get it from our freshly generated opp table.
>> It's not reached in this code path.
> 
> I see. I got lost in all the ifs. What do you think about turning it into the main code path, since after this code block we always have a valid OPP table?
Sounds good!

Konrad
> 
>>
>>>
>>>> +        } else if (adreno_is_a320(adreno_gpu)) {
>>>> +            dev_warn(dev, "Unable to find the OPP table. Falling back to 450 MHz.\n");
>>>> +            dev_pm_opp_add(dev, 450000000, 0);
>>>> +            gpu->fast_rate = 450000000;
>>>> +        } else {
>>>> +            DRM_DEV_ERROR(dev, "Unable to find the OPP table\n");
>>>> +            return -ENODEV;
>>>> +        }
>>>> +    } else if (ret) {
>>>> +        DRM_DEV_ERROR(dev, "Unable to set the OPP table\n");
>>>> +        return ret;
>>>> +    } else {
>>>>            /* Find the fastest defined rate */
>>>>            opp = dev_pm_opp_find_freq_floor(dev, &freq);
>>>> -        if (!IS_ERR(opp)) {
>>>> +
>>>> +        if (IS_ERR(opp))
>>>> +            return PTR_ERR(opp);
>>>> +        else {
>>>>                gpu->fast_rate = freq;
>>>>                dev_pm_opp_put(opp);
>>>>            }
>>>>        }
>>>>    -    if (!gpu->fast_rate) {
>>>> -        dev_warn(dev,
>>>> -            "Could not find a clock rate. Using a reasonable default\n");
>>>> -        /* Pick a suitably safe clock speed for any target */
>>>> -        gpu->fast_rate = 200000000;
>>>> -    }
>>>> -
>>>>        DBG("fast_rate=%u, slow_rate=27000000", gpu->fast_rate);
>>>> +
>>>> +    return 0;
>>>>    }
>>>>      int adreno_gpu_ocmem_init(struct device *dev, struct adreno_gpu *adreno_gpu,
> 
>