On 11/14/2025 2:42 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]>
Reviewed-by: Mario Limonciello (AMD) <[email protected]>> ---
Documentation/gpu/amdgpu/driver-misc.rst | 26 ++++++++++++++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 29 +++++++++++++++++++++++++++++
2 files changed, 55 insertions(+)
diff --git a/Documentation/gpu/amdgpu/driver-misc.rst
b/Documentation/gpu/amdgpu/driver-misc.rst
index 25b0c857816e..afefab4fa0ac 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 implementations.
+
+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
+be created at all.
+
+uma_carveout_options
+--------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+ :doc: uma_carveout_options
+
+uma_carveout
+--------------------
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+ :doc: uma_carveout
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index b9378f34eb79..10cc6bf28a0f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -1248,6 +1248,24 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev,
int xcc_id,
return -ENOENT;
}
+/**
+ * DOC: uma_carveout_options
+ *
+ * This is a read-only file that lists all available UMA allocation
+ * options and their corresponding indices. Example output::
+ *
+ * $ cat uma_carveout_options
+ * 0: Minimum (0 GB)
+ * 1: (1 GB)
+ * 2: (2 GB)
+ * 3: (4 GB)
+ * 4: (6 GB)
+ * 5: (8 GB)
+ * 6: (12 GB)
+ * 7: Medium (16 GB)
+ * 8: (24 GB)
+ * 9: High (32 GB)
+ */
static ssize_t uma_carveout_options_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -1269,6 +1287,17 @@ static ssize_t uma_carveout_options_show(struct device
*dev,
}
static DEVICE_ATTR_RO(uma_carveout_options);
+/**
+ * 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)
