linux-kernel - Re: [PATCH] drm/msm/adreno: fix gpu probe if no interconnect-names

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Message-ID: <baef95e0-e44f-be7d-f60f-0ba75b550050@marek.ca>
Date:   Wed, 15 Jul 2020 14:36:33 -0400
From:   Jonathan Marek <jonathan@...ek.ca>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     Rob Clark <robdclark@...omium.org>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Brian Masney <masneyb@...tation.org>,
        John Stultz <john.stultz@...aro.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/adreno: fix gpu probe if no interconnect-names

On 7/15/20 2:29 PM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> If there is no interconnect-names, but there is an interconnects
> property, then of_icc_get(dev, "gfx-mem"); would return an error
> rather than NULL.
> 
> Also, if there is no interconnect-names property, there will never
> be a ocmem path.  But of_icc_get(dev, "ocmem") would return -EINVAL
> instead of -ENODATA.  Just don't bother trying in this case.
> 
> Fixes: 8e29fb37b301 ("drm/msm: handle for EPROBE_DEFER for of_icc_get")
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>   drivers/gpu/drm/msm/adreno/adreno_gpu.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index 0527e85184e1..c4ac998b90c8 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -979,6 +979,7 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>   	struct adreno_platform_config *config = dev->platform_data;
>   	struct msm_gpu_config adreno_gpu_config  = { 0 };
>   	struct msm_gpu *gpu = &adreno_gpu->base;
> +	bool has_interconnect_names = true;
>   	int ret;
>   
>   	adreno_gpu->funcs = funcs;
> @@ -1005,12 +1006,13 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>   
>   	/* Check for an interconnect path for the bus */
>   	gpu->icc_path = of_icc_get(dev, "gfx-mem");
> -	if (!gpu->icc_path) {
> +	if (IS_ERR_OR_NULL(gpu->icc_path)) {
>   		/*
>   		 * Keep compatbility with device trees that don't have an
>   		 * interconnect-names property.
>   		 */
>   		gpu->icc_path = of_icc_get(dev, NULL);

This is misleading because if it gets a EPROBE_DEFER error (or any other 
error), it will hit this path. Maybe there's a specific error you can 
check for instead to identify the "no-interconnect-names" case?

Also don't think its a good idea to be calling of_icc_get(dev, NULL) 
again when there's a EPROBE_DEFER, the interconnect driver could come up 
between the two calls

> +		has_interconnect_names = false;
>   	}
>   	if (IS_ERR(gpu->icc_path)) {
>   		ret = PTR_ERR(gpu->icc_path);
> @@ -1018,7 +1020,9 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>   		return ret;
>   	}
>   
> -	gpu->ocmem_icc_path = of_icc_get(dev, "ocmem");
> +	if (has_interconnect_names)
> +		gpu->ocmem_icc_path = of_icc_get(dev, "ocmem");
> +
>   	if (IS_ERR(gpu->ocmem_icc_path)) {
>   		ret = PTR_ERR(gpu->ocmem_icc_path);
>   		gpu->ocmem_icc_path = NULL;
>