linux-kernel - Re: [PATCH v2 5/9] drm/panthor: Make getting GPU model name simple and extensible

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Message-ID: <20250321090254.667a86cb@collabora.com>
Date: Fri, 21 Mar 2025 09:02:54 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Karunika Choo <karunika.choo@....com>
Cc: dri-devel@...ts.freedesktop.org, nd@....com, Steven Price
 <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>, Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/9] drm/panthor: Make getting GPU model name simple
 and extensible

On Thu, 20 Mar 2025 11:17:37 +0000
Karunika Choo <karunika.choo@....com> wrote:

> This patch replaces the previous panthor_model structure with a simple
> switch case based on the product_id, which is in the format of:
>         ((arch_major << 24) | product_major)
> 
> This not only simplifies the comparison, but also allows extending the
> function to accommodate naming differences based on GPU features.
> 
> Signed-off-by: Karunika Choo <karunika.choo@....com>
> ---
>  drivers/gpu/drm/panthor/panthor_hw.c   | 63 +++++++-------------------
>  drivers/gpu/drm/panthor/panthor_regs.h |  1 +
>  2 files changed, 18 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_hw.c b/drivers/gpu/drm/panthor/panthor_hw.c
> index 4cc4b0d5382c..12183c04cd21 100644
> --- a/drivers/gpu/drm/panthor/panthor_hw.c
> +++ b/drivers/gpu/drm/panthor/panthor_hw.c
> @@ -5,40 +5,6 @@
>  #include "panthor_hw.h"
>  #include "panthor_regs.h"
>  
> -/**
> - * struct panthor_model - GPU model description
> - */
> -struct panthor_model {
> -	/** @name: Model name. */
> -	const char *name;
> -
> -	/** @arch_major: Major version number of architecture. */
> -	u8 arch_major;
> -
> -	/** @product_major: Major version number of product. */
> -	u8 product_major;
> -};
> -
> -/**
> - * GPU_MODEL() - Define a GPU model. A GPU product can be uniquely identified
> - * by a combination of the major architecture version and the major product
> - * version.
> - * @_name: Name for the GPU model.
> - * @_arch_major: Architecture major.
> - * @_product_major: Product major.
> - */
> -#define GPU_MODEL(_name, _arch_major, _product_major) \
> -{\
> -	.name = __stringify(_name),				\
> -	.arch_major = _arch_major,				\
> -	.product_major = _product_major,			\
> -}
> -
> -static const struct panthor_model gpu_models[] = {
> -	GPU_MODEL(g610, 10, 7),
> -	{},
> -};
> -
>  static void arch_10_8_gpu_info_init(struct panthor_device *ptdev)
>  {
>  	unsigned int i;
> @@ -66,29 +32,34 @@ static void arch_10_8_gpu_info_init(struct panthor_device *ptdev)
>  	ptdev->gpu_info.l2_present = gpu_read64(ptdev, GPU_L2_PRESENT_LO);
>  }
>  
> +static char *get_gpu_model_name(struct panthor_device *ptdev)
> +{
> +	const u32 gpu_id = ptdev->gpu_info.gpu_id;
> +	const u32 product_id = GPU_PROD_ID_MAKE(GPU_ARCH_MAJOR(gpu_id),
> +						GPU_PROD_MAJOR(gpu_id));
> +
> +	switch (product_id) {
> +	case GPU_PROD_ID_MAKE(10, 7):
> +		return "Mali-G610";
> +	}

I a big fan of these ever growing switch statements with nested
conditionals. Could we instead add an optional ::get_variant() callback
in panthor_model and have the following formatting:

	"Mali-%s%s%s", model->name,
		       model->get_variant ? "-" : "",
		       model->get_variant ? model->get_variant() : ""

> +
> +	return "(Unknown Mali GPU)";
> +}
> +
>  static void panthor_gpu_init_info(struct panthor_device *ptdev)
>  {
> -	const struct panthor_model *model;
> -	u32 arch_major, product_major;
> +	const char *gpu_model_name = get_gpu_model_name(ptdev);
>  	u32 major, minor, status;
>  
>  	ptdev->hw->ops.gpu_info_init(ptdev);
>  
> -	arch_major = GPU_ARCH_MAJOR(ptdev->gpu_info.gpu_id);
> -	product_major = GPU_PROD_MAJOR(ptdev->gpu_info.gpu_id);
>  	major = GPU_VER_MAJOR(ptdev->gpu_info.gpu_id);
>  	minor = GPU_VER_MINOR(ptdev->gpu_info.gpu_id);
>  	status = GPU_VER_STATUS(ptdev->gpu_info.gpu_id);
>  
> -	for (model = gpu_models; model->name; model++) {
> -		if (model->arch_major == arch_major &&
> -		    model->product_major == product_major)
> -			break;
> -	}
> -
>  	drm_info(&ptdev->base,
> -		 "mali-%s id 0x%x major 0x%x minor 0x%x status 0x%x",
> -		 model->name ?: "unknown", ptdev->gpu_info.gpu_id >> 16,
> +		 "%s id 0x%x major 0x%x minor 0x%x status 0x%x",
> +		 gpu_model_name, ptdev->gpu_info.gpu_id >> 16,
>  		 major, minor, status);
>  
>  	drm_info(&ptdev->base,
> diff --git a/drivers/gpu/drm/panthor/panthor_regs.h b/drivers/gpu/drm/panthor/panthor_regs.h
> index ba452c1dd644..d9e0769d6f1a 100644
> --- a/drivers/gpu/drm/panthor/panthor_regs.h
> +++ b/drivers/gpu/drm/panthor/panthor_regs.h
> @@ -20,6 +20,7 @@
>  #define   GPU_VER_STATUS(x)				((x) & GENMASK(3, 0))
>  
>  #define GPU_ARCH_ID_MAKE(major, minor, rev)		(((major) << 16) | ((minor) << 8) | (rev))
> +#define GPU_PROD_ID_MAKE(arch_major, prod_major)	(((arch_major) << 24) | (prod_major))
>  
>  #define GPU_L2_FEATURES					0x4
>  #define  GPU_L2_FEATURES_LINE_SIZE(x)			(1 << ((x) & GENMASK(7, 0)))