linux-kernel - Re: [Freedreno] [PATCH v3 4/7] drm/msm/a2xx: Implement .gpu

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Message-ID: <8e9fc1c0-f74f-ba82-fade-31212637d6bb@linaro.org>
Date:   Mon, 13 Mar 2023 17:54:55 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Jonathan Marek <jonathan@...ek.ca>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [Freedreno] [PATCH v3 4/7] drm/msm/a2xx: Implement .gpu_busy



On 24.02.2023 16:04, Jonathan Marek wrote:
> This won't work because a2xx freedreno userspace expects to own all the perfcounters.
> 
> This will break perfcounters for userspace, and when userspace isn't using perfcounters, this won't count correctly because userspace writes 0 to CP_PERFMON_CNTL at the start of every submit.

Rob, would you be willing to take this without the a2xx bits? It
should still be fine, except without devfreq. Not that we had
any significant sort of scaling on a2xx before.

Konrad
> 
> On 2/23/23 5:52 AM, Konrad Dybcio wrote:
>> Implement gpu_busy based on the downstream msm-3.4 code [1]. This
>> allows us to use devfreq on this old old old hardware!
>>
>> [1] https://github.com/LineageOS/android_kernel_sony_apq8064/blob/lineage-16.0/drivers/gpu/msm/adreno_a2xx.c#L1975
>>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---
>>   drivers/gpu/drm/msm/adreno/a2xx_gpu.c | 26 ++++++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
>> index c67089a7ebc1..104bdf28cdaf 100644
>> --- a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
>> @@ -481,6 +481,31 @@ a2xx_create_address_space(struct msm_gpu *gpu, struct platform_device *pdev)
>>       return aspace;
>>   }
>>   +/* While the precise size of this field is unknown, it holds at least these three values.. */
>> +static u64 a2xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
>> +{
>> +    u64 busy_cycles;
>> +
>> +    /* Freeze the counter */
>> +    gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_FREEZE);
>> +
>> +    busy_cycles = gpu_read64(gpu, REG_A2XX_RBBM_PERFCOUNTER1_LO);
>> +
>> +    /* Reset the counter */
>> +    gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_RESET);
>> +
>> +    /* Re-enable the performance monitors */
>> +    gpu_rmw(gpu, REG_A2XX_RBBM_PM_OVERRIDE2,
>> +        A2XX_RBBM_PM_OVERRIDE2_DEBUG_PERF_SCLK_PM_OVERRIDE,
>> +        A2XX_RBBM_PM_OVERRIDE2_DEBUG_PERF_SCLK_PM_OVERRIDE);
>> +    gpu_write(gpu, REG_A2XX_RBBM_PERFCOUNTER1_SELECT, 1);
>> +    gpu_write(gpu, REG_A2XX_CP_PERFMON_CNTL, PERF_STATE_ENABLE);
>> +
>> +    *out_sample_rate = clk_get_rate(gpu->core_clk);
>> +
>> +    return busy_cycles;
>> +}
>> +
>>   static u32 a2xx_get_rptr(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
>>   {
>>       ring->memptrs->rptr = gpu_read(gpu, REG_AXXX_CP_RB_RPTR);
>> @@ -502,6 +527,7 @@ static const struct adreno_gpu_funcs funcs = {
>>   #if defined(CONFIG_DEBUG_FS) || defined(CONFIG_DEV_COREDUMP)
>>           .show = adreno_show,
>>   #endif
>> +        .gpu_busy = a2xx_gpu_busy,
>>           .gpu_state_get = a2xx_gpu_state_get,
>>           .gpu_state_put = adreno_gpu_state_put,
>>           .create_address_space = a2xx_create_address_space,
>>