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) <[email protected]>
---
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)
