linux-kernel - Re: [PATCH 5/6] drm: msm: a6xx: use dev_pm_opp_set

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Message-ID: <20200518142333.GA10796@jcrouse1-lnx.qualcomm.com>
Date:   Mon, 18 May 2020 08:23:34 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Sharat Masetty <smasetty@...eaurora.org>
Cc:     freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
        dri-devel@...edesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, georgi.djakov@...aro.org,
        mka@...omium.org
Subject: Re: [PATCH 5/6] drm: msm: a6xx: use dev_pm_opp_set_bw to set DDR
 bandwidth

On Thu, May 14, 2020 at 04:24:18PM +0530, Sharat Masetty wrote:
> This patches replaces the previously used static DDR vote and uses
> dev_pm_opp_set_bw() to scale GPU->DDR bandwidth along with scaling
> GPU frequency.
> 
> Signed-off-by: Sharat Masetty <smasetty@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index 2d8124b..79433d3 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -141,11 +141,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
> 
>  	gmu->freq = gmu->gpu_freqs[perf_index];
> 
> -	/*
> -	 * Eventually we will want to scale the path vote with the frequency but
> -	 * for now leave it at max so that the performance is nominal.
> -	 */
> -	icc_set_bw(gpu->icc_path, 0, MBps_to_icc(7216));
> +	dev_pm_opp_set_bw(&gpu->pdev->dev, opp);
>  }

This adds an implicit requirement that all targets need bandwidth settings
defined in the OPP or they won't get a bus vote at all. I would prefer that
there be an default escape valve but if not you'll need to add
bandwidth values for the sdm845 OPP that target doesn't regress.

Jordan

>  unsigned long a6xx_gmu_get_freq(struct msm_gpu *gpu)
> --
> 2.7.4
> 

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