linux-kernel - Re: [PATCH 5/5] Documentation/amdgpu: Add UMA carveout details

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Message-ID: <a0802bd3-2998-4149-8035-4fbd73ce911f@kernel.org>
Date: Mon, 3 Nov 2025 11:45:11 -0600
From: "Mario Limonciello (AMD) (kernel.org)" <superm1@...nel.org>
To: "Yo-Jung Leo Lin (AMD)" <Leo.Lin@....com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Jonathan Corbet <corbet@....net>
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, anson.tsao@....com
Subject: Re: [PATCH 5/5] Documentation/amdgpu: Add UMA carveout details



On 11/3/2025 1:51 AM, Yo-Jung Leo Lin (AMD) wrote:
> Add documentation for the uma_carveout_options and uma_carveout
> attributes in sysfs
> 
> Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@....com>
> ---
>   Documentation/gpu/amdgpu/driver-misc.rst     | 26 ++++++++++++++++++++++++++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 17 +++++++++++++++++
>   2 files changed, 43 insertions(+)
> 
> diff --git a/Documentation/gpu/amdgpu/driver-misc.rst b/Documentation/gpu/amdgpu/driver-misc.rst
> index 25b0c857816e..5a71fa9c6782 100644
> --- a/Documentation/gpu/amdgpu/driver-misc.rst
> +++ b/Documentation/gpu/amdgpu/driver-misc.rst
> @@ -128,3 +128,29 @@ smartshift_bias
>   
>   .. kernel-doc:: drivers/gpu/drm/amd/pm/amdgpu_pm.c
>      :doc: smartshift_bias
> +
> +UMA Carveout
> +============
> +
> +Some versions of Atom ROM expose available options for the VRAM carveout sizes,
> +and allow changes to the carveout size via the ATCS function code 0xA on supported
> +BIOS implementation.
> +
> +For those platforms, users can use the following file to set the carveout size,
> +in a way similar to what Windows users can do in the "Tuning" tab in AMD
> +Adrenalin.
> +
> +Note that for BIOS implementations that don't support this, these files will not
> +get created at all.
> +
> +uma_carveout_options
> +--------------------
> +
> +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> +   :doc: uma_carveout_options
> +
> +uma_carveout
> +--------------------
> +
> +.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> +   :doc: uma_carveout

How do you feel about adding some sample output from a test system for 
both files?  This might make it easier for userspace to implement 
parsing it.

> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> index 1ebfd925b761..e9f71888ce57 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> @@ -1855,6 +1855,17 @@ const struct attribute_group amdgpu_vbios_version_attr_group = {
>   	.is_visible = amdgpu_vbios_version_attrs_is_visible,
>   };
>   
> +/**
> + * DOC: uma_carveout
> + *
> + * This file is both readable and writable. When read, it shows the
> + * index of the current setting. Writing a valid index to this file
> + * allows users to change the UMA carveout size to the selected option
> + * on the next boot.
> + *
> + * The available options and their corresponding indices can be read
> + * from the uma_carveout_options file.
> + */
>   static ssize_t uma_carveout_show(struct device *dev,
>   				 struct device_attribute *attr,
>   				 char *buf)
> @@ -1904,6 +1915,12 @@ static ssize_t uma_carveout_store(struct device *dev,
>   }
>   static DEVICE_ATTR_RW(uma_carveout);
>   
> +/**
> + * DOC: uma_carveout_options
> + *
> + * This is a read-only file that lists all available UMA allocation
> + * options and their corresponding indices.
> + */
>   static ssize_t uma_carveout_options_show(struct device *dev,
>   					 struct device_attribute *attr,
>   					 char *buf)
>