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

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Date:   Fri, 24 Feb 2023 10:04:19 -0500
From:   Jonathan Marek <jonathan@...ek.ca>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        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

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.

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,
>