[PATCH v2 5/5] drm/msm/A6xx: Add devfreq support for A6xx

[Jordan Crouse]

On Mon, Aug 27, 2018 at 12:47:20PM +0530, Sharat Masetty wrote:
> Implement routines to estimate GPU busy time and fetching the
> current frequency for the polling interval. This is required by
> the devfreq framework which recommends a frequency change if needed.
> The driver code then tries to set this new frequency on the GPU by
> sending an Out Of Band(OOB) request to the GMU.
> 
> Signed-off-by: Sharat Masetty <smasetty at codeaurora.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 39 +++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  2 ++
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 27 ++++++++++++++++++++++++
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.h |  2 ++
>  4 files changed, 66 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index f6634c0..3a7b899 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -67,7 +67,7 @@ static bool a6xx_gmu_gx_is_on(struct a6xx_gmu *gmu)
>  		A6XX_GMU_SPTPRAC_PWR_CLK_STATUS_GX_HM_CLK_OFF));
>  }
>  
> -static int a6xx_gmu_set_freq(struct a6xx_gmu *gmu, int index)
> +static int __a6xx_gmu_set_freq(struct a6xx_gmu *gmu, int index)
>  {
>  	gmu_write(gmu, REG_A6XX_GMU_DCVS_ACK_OPTION, 0);
>  
> @@ -84,7 +84,38 @@ static int a6xx_gmu_set_freq(struct a6xx_gmu *gmu, int index)
>  	a6xx_gmu_set_oob(gmu, GMU_OOB_DCVS_SET);
>  	a6xx_gmu_clear_oob(gmu, GMU_OOB_DCVS_SET);
>  
> -	return gmu_read(gmu, REG_A6XX_GMU_DCVS_RETURN);
> +	if (gmu_read(gmu, REG_A6XX_GMU_DCVS_RETURN) != 0)
> +		return -EINVAL;
> +
> +	gmu->freq = gmu->gpu_freqs[index];
> +
> +	return 0;
> +}

While I was working on the interconnect patches it occurred to me that the upper
levels doesn't really care what the value of A6XX_GMU_DCVS_RETURN is so we might
want to just print an error message and return nothing. If the DCVS set didn't
work we might be headed for disaster on the GMU side but its more likely that
we'll just continue along at the current frequency for the next cycle so it
isn't terribly harmful.

Jordan

-- 
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project