linux-kernel - Re: [PATCH v2 1/3] drm/msm/adreno: Add support for ACD

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Message-ID: <3ee7a1c9-2d6d-4fd5-982e-d86151e45662@linaro.org>
Date: Tue, 22 Oct 2024 10:07:55 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>, Rob Clark
 <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
 Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] drm/msm/adreno: Add support for ACD

On 21/10/2024 12:53, Akhil P Oommen wrote:
> ACD a.k.a Adaptive Clock Distribution is a feature which helps to reduce
> the power consumption. In some chipsets, it is also a requirement to
> support higher GPU frequencies. This patch adds support for GPU ACD by
> sending necessary data to GMU and AOSS. The feature support for the
> chipset is detected based on devicetree data.
> 
> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> ---
>   drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 81 ++++++++++++++++++++++++++++-------
>   drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  1 +
>   drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 36 ++++++++++++++++
>   drivers/gpu/drm/msm/adreno/a6xx_hfi.h | 21 +++++++++
>   4 files changed, 124 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index 37927bdd6fbe..09fb3f397dbb 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -1021,14 +1021,6 @@ int a6xx_gmu_resume(struct a6xx_gpu *a6xx_gpu)
>   
>   	gmu->hung = false;
>   
> -	/* Notify AOSS about the ACD state (unimplemented for now => disable it) */
> -	if (!IS_ERR(gmu->qmp)) {
> -		ret = qmp_send(gmu->qmp, "{class: gpu, res: acd, val: %d}",
> -			       0 /* Hardcode ACD to be disabled for now */);
> -		if (ret)
> -			dev_err(gmu->dev, "failed to send GPU ACD state\n");
> -	}
> -
>   	/* Turn on the resources */
>   	pm_runtime_get_sync(gmu->dev);
>   
> @@ -1476,6 +1468,64 @@ static int a6xx_gmu_pwrlevels_probe(struct a6xx_gmu *gmu)
>   	return a6xx_gmu_rpmh_votes_init(gmu);
>   }
>   
> +static int a6xx_gmu_acd_probe(struct a6xx_gmu *gmu)
> +{
> +	struct a6xx_gpu *a6xx_gpu = container_of(gmu, struct a6xx_gpu, gmu);
> +	struct a6xx_hfi_acd_table *cmd = &gmu->acd_table;
> +	struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
> +	struct msm_gpu *gpu = &adreno_gpu->base;
> +	int ret, i, cmd_idx = 0;
> +
> +	cmd->version = 1;
> +	cmd->stride = 1;
> +	cmd->enable_by_level = 0;
> +
> +	/* Skip freq = 0 and parse acd-level for rest of the OPPs */
> +	for (i = 1; i < gmu->nr_gpu_freqs; i++) {
> +		struct dev_pm_opp *opp;
> +		struct device_node *np;
> +		unsigned long freq;
> +		u32 val;
> +
> +		freq = gmu->gpu_freqs[i];
> +		opp = dev_pm_opp_find_freq_exact(&gpu->pdev->dev, freq, true);
> +		np = dev_pm_opp_get_of_node(opp);
> +
> +		ret = of_property_read_u32(np, "qcom,opp-acd-level", &val);
> +		of_node_put(np);
> +		dev_pm_opp_put(opp);
> +		if (ret == -EINVAL)
> +			continue;
> +		else if (ret) {
> +			DRM_DEV_ERROR(gmu->dev, "Unable to read acd level for freq %lu\n", freq);
> +			return ret;
> +		}
> +
> +		cmd->enable_by_level |= BIT(i);
> +		cmd->data[cmd_idx++] = val;

How do you know that cmd_idx is always < sizeof(cmd->data); ?

> +	}
> +
> +	cmd->num_levels = cmd_idx;
> +
> +	/* We are done here if ACD is not required for any of the OPPs */
> +	if (!cmd->enable_by_level)
> +		return 0;
> +
> +	/* Initialize qmp node to talk to AOSS */
> +	gmu->qmp = qmp_get(gmu->dev);
> +	if (IS_ERR(gmu->qmp)) {
> +		cmd->enable_by_level = 0;
> +		return dev_err_probe(gmu->dev, PTR_ERR(gmu->qmp), "Failed to initialize qmp\n");
> +	}
> +
> +	/* Notify AOSS about the ACD state */
> +	ret = qmp_send(gmu->qmp, "{class: gpu, res: acd, val: %d}", 1);
> +	if (ret)
> +		DRM_DEV_ERROR(gmu->dev, "failed to send GPU ACD state\n");
> +
> +	return 0;

Shouldn't the ret from gmp_send() get propogated in the return of this 
function ?

i.e. how can your probe be successful if the notification failed ?

---
bod