linux-kernel - Re: [v1] drm/msm/disp/dpu1: fix warn stack reported during dpu resume

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Message-ID: <84fdbdc7-7890-965a-bc6b-a19bd0ca4937@linaro.org>
Date:   Wed, 31 Mar 2021 19:03:33 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kalyan Thota <kalyan_t@...eaurora.org>, y@...lcomm.com,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, robdclark@...il.com,
        dianders@...omium.org, mkrishn@...eaurora.org, hywu@...gle.com,
        mka@...gle.com, midean@...gle.com, steev@...i.org
Subject: Re: [v1] drm/msm/disp/dpu1: fix warn stack reported during dpu resume

On 31/03/2021 14:27, Kalyan Thota wrote:
> WARN_ON was introduced by the below commit to catch runtime resumes
> that are getting triggered before icc path was set.
> 
> "drm/msm/disp/dpu1: icc path needs to be set before dpu runtime resume"
> 
> For the targets where the bw scaling is not enabled, this WARN_ON is
> a false alarm. Fix the WARN condition appropriately.

Should we change all DPU targets to use bw scaling to the mdp from the 
mdss nodes? The limitation to sc7180 looks artificial.

> 
> Reported-by: Steev Klimaszewski <steev@...i.org>
> Signed-off-by: Kalyan Thota <kalyan_t@...eaurora.org>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c  |  8 +++++---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h  |  9 +++++++++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c | 11 ++++++-----
>   3 files changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index cab387f..0071a4d 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -294,6 +294,9 @@ static int dpu_kms_parse_data_bus_icc_path(struct dpu_kms *dpu_kms)
>   	struct icc_path *path1;
>   	struct drm_device *dev = dpu_kms->dev;
>   
> +	if (!dpu_supports_bw_scaling(dev))
> +		return 0;
> +
>   	path0 = of_icc_get(dev->dev, "mdp0-mem");
>   	path1 = of_icc_get(dev->dev, "mdp1-mem");
>   
> @@ -934,8 +937,7 @@ static int dpu_kms_hw_init(struct msm_kms *kms)
>   		DPU_DEBUG("REG_DMA is not defined");
>   	}
>   
> -	if (of_device_is_compatible(dev->dev->of_node, "qcom,sc7180-mdss"))
> -		dpu_kms_parse_data_bus_icc_path(dpu_kms);
> +	dpu_kms_parse_data_bus_icc_path(dpu_kms);
>   
>   	pm_runtime_get_sync(&dpu_kms->pdev->dev);
>   
> @@ -1198,7 +1200,7 @@ static int __maybe_unused dpu_runtime_resume(struct device *dev)
>   
>   	ddev = dpu_kms->dev;
>   
> -	WARN_ON(!(dpu_kms->num_paths));
> +	WARN_ON((dpu_supports_bw_scaling(ddev) && !dpu_kms->num_paths));
>   	/* Min vote of BW is required before turning on AXI clk */
>   	for (i = 0; i < dpu_kms->num_paths; i++)
>   		icc_set_bw(dpu_kms->path[i], 0, Bps_to_icc(MIN_IB_BW));
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> index d6717d6..f7bcc0a 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> @@ -154,6 +154,15 @@ struct vsync_info {
>   
>   #define to_dpu_global_state(x) container_of(x, struct dpu_global_state, base)
>   
> +/**
> + * dpu_supports_bw_scaling: returns true for drivers that support bw scaling.
> + * @dev: Pointer to drm_device structure
> + */
> +static inline int dpu_supports_bw_scaling(struct drm_device *dev)
> +{
> +	return of_device_is_compatible(dev->dev->of_node, "qcom,sc7180-mdss");
> +}
> +
>   /* Global private object state for tracking resources that are shared across
>    * multiple kms objects (planes/crtcs/etc).
>    */
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> index cd40788..8cd712c 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> @@ -41,6 +41,9 @@ static int dpu_mdss_parse_data_bus_icc_path(struct drm_device *dev,
>   	struct icc_path *path0 = of_icc_get(dev->dev, "mdp0-mem");
>   	struct icc_path *path1 = of_icc_get(dev->dev, "mdp1-mem");
>   
> +	if (dpu_supports_bw_scaling(dev))
> +		return 0;
> +
>   	if (IS_ERR_OR_NULL(path0))
>   		return PTR_ERR_OR_ZERO(path0);
>   
> @@ -276,11 +279,9 @@ int dpu_mdss_init(struct drm_device *dev)
>   
>   	DRM_DEBUG("mapped mdss address space @%pK\n", dpu_mdss->mmio);
>   
> -	if (!of_device_is_compatible(dev->dev->of_node, "qcom,sc7180-mdss")) {
> -		ret = dpu_mdss_parse_data_bus_icc_path(dev, dpu_mdss);
> -		if (ret)
> -			return ret;
> -	}
> +	ret = dpu_mdss_parse_data_bus_icc_path(dev, dpu_mdss);
> +	if (ret)
> +		return ret;
>   
>   	mp = &dpu_mdss->mp;
>   	ret = msm_dss_parse_clock(pdev, mp);
> 


-- 
With best wishes
Dmitry