linux-kernel - Re: [PATCH 2/9] drm/panfrost: handle inexistent GPU during probe

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Message-ID: <20241021160642.1dbeb772@collabora.com>
Date: Mon, 21 Oct 2024 16:06:42 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>, Simona
 Vetter <simona@...ll.ch>
Cc: Rob Herring <robh@...nel.org>, Steven Price <steven.price@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Philipp Zabel <p.zabel@...gutronix.de>,
 kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] drm/panfrost: handle inexistent GPU during probe

On Tue, 15 Oct 2024 00:31:37 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> Just in case we're dealing with a yet not recognised device.

While I can see how problematic it would be if we expose a GPU that
requires kernel quirks we don't know about, I suspect the original
authors had a good reason to allow probing of unknown GPUs (ease of GPU
bringup), so I'll defer that one to Steve and Rob.

> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_gpu.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> index 5a33919fa213..495621324de1 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> @@ -237,9 +237,10 @@ static const struct panfrost_model gpu_models[] = {
>  	 */
>  	GPU_MODEL(g57, 0x9003,
>  		GPU_REV(g57, 0, 0)),
> +	{0},
>  };
>  
> -static void panfrost_gpu_init_features(struct panfrost_device *pfdev)
> +static int panfrost_gpu_init_features(struct panfrost_device *pfdev)
>  {
>  	u32 gpu_id, num_js, major, minor, status, rev;
>  	const char *name = "unknown";
> @@ -324,6 +325,12 @@ static void panfrost_gpu_init_features(struct panfrost_device *pfdev)
>  		break;
>  	}
>  
> +	if (!model->name) {
> +		dev_err(pfdev->base.dev, "GPU model not found: mali-%s id rev %#x %#x\n",
> +			name, gpu_id, rev);
> +		return -ENODEV;
> +	}
> +
>  	bitmap_from_u64(pfdev->features.hw_features, hw_feat);
>  	bitmap_from_u64(pfdev->features.hw_issues, hw_issues);
>  
> @@ -344,6 +351,8 @@ static void panfrost_gpu_init_features(struct panfrost_device *pfdev)
>  
>  	dev_info(pfdev->base.dev, "shader_present=0x%0llx l2_present=0x%0llx",
>  		 pfdev->features.shader_present, pfdev->features.l2_present);
> +
> +	return 0;
>  }
>  
>  void panfrost_cycle_counter_get(struct panfrost_device *pfdev)
> @@ -486,7 +495,9 @@ int panfrost_gpu_init(struct panfrost_device *pfdev)
>  	if (err)
>  		return err;
>  
> -	panfrost_gpu_init_features(pfdev);
> +	err = panfrost_gpu_init_features(pfdev);
> +	if (err)
> +		return err;
>  
>  	err = dma_set_mask_and_coherent(pfdev->base.dev,
>  					DMA_BIT_MASK(FIELD_GET(0xff00,