Add two sysfs files as interfaces to inspect or change UMA carveout
size. These files are:

- uma_carveout_options: a read-only file listing all the available
  UMA allocation options and their index.

- uma_carveout: a file that is both readable and writable. On read,
  it shows the index of the current setting. Writing a valid index
  into this file allows users to change the UMA carveout size to that
  option on the next boot.

Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 127 +++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index 444ab4102168..b9378f34eb79 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -30,6 +30,7 @@
 #include <linux/power_supply.h>
 #include <linux/pm_runtime.h>
 #include <linux/suspend.h>
+#include <linux/device.h>
 #include <acpi/video.h>
 #include <acpi/actbl.h>
 
@@ -1247,6 +1248,125 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
 	return -ENOENT;
 }
 
+static ssize_t uma_carveout_options_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+	ssize_t size = 0;
+
+	if (!uma_info || !uma_info->num_entries)
+		return -ENODEV;
+
+	for (int i = 0; i < uma_info->num_entries; i++) {
+		size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
+				      i,
+				      uma_info->entries[i].name,
+				      uma_info->entries[i].memory_carved);
+	}
+
+	return size;
+}
+static DEVICE_ATTR_RO(uma_carveout_options);
+
+static ssize_t uma_carveout_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	return sysfs_emit(buf, "%u\n", amdgpu_acpi_priv.atcs.uma_info.uma_option_index);
+}
+
+static ssize_t uma_carveout_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	struct amdgpu_uma_carveout_option *opt;
+	unsigned long val;
+	uint8_t flags;
+	int r;
+
+	r = kstrtoul(buf, 10, &val);
+	if (r)
+		return r;
+
+	if (val >= uma_info->num_entries)
+		return -EINVAL;
+
+	opt = &uma_info->entries[val];
+
+	if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
+	    !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
+		drm_err_once(ddev, "Option %ul not supported due to lack of Custom/Auto flag", r);
+		return -EINVAL;
+	}
+
+	flags = opt->flags;
+	flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
+
+	guard(mutex)(&uma_info->update_lock);
+
+	r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
+	if (r)
+		return r;
+
+	uma_info->uma_option_index = val;
+
+	return count;
+}
+static DEVICE_ATTR_RW(uma_carveout);
+
+static struct attribute *amdgpu_uma_attrs[] = {
+	&dev_attr_uma_carveout.attr,
+	&dev_attr_uma_carveout_options.attr,
+	NULL
+};
+
+const struct attribute_group amdgpu_uma_attr_group = {
+	.attrs = amdgpu_uma_attrs
+};
+
+static int amdgpu_acpi_uma_option_init(struct amdgpu_device *adev)
+{
+	struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
+	int rc;
+
+	if (!atcs->functions.set_uma_allocation_size)
+		return -ENODEV;
+
+	rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &atcs->uma_info);
+	if (rc) {
+		drm_dbg(adev_to_drm(adev),
+			"Failed to parse UMA carveout info from VBIOS: %d\n", rc);
+		goto out_info;
+	}
+
+	mutex_init(&atcs->uma_info.update_lock);
+
+	rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
+	if (rc) {
+		drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs interfaces %d\n", rc);
+		goto out_attr;
+	}
+
+	return 0;
+
+out_attr:
+	mutex_destroy(&atcs->uma_info.update_lock);
+out_info:
+	return rc;
+}
+
+static void amdgpu_acpi_uma_option_fini(void)
+{
+	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
+
+	mutex_destroy(&uma_info->update_lock);
+	uma_info->num_entries = 0;
+}
+
 /**
  * amdgpu_acpi_event - handle notify events
  *
@@ -1291,6 +1411,12 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
 int amdgpu_acpi_init(struct amdgpu_device *adev)
 {
 	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
+	int rc;
+
+	rc = amdgpu_acpi_uma_option_init(adev);
+
+	if (rc)
+		drm_dbg(adev_to_drm(adev), "Not creating uma carveout interfaces: %d", rc);
 
 	if (atif->notifications.brightness_change) {
 		if (adev->dc_enabled) {
@@ -1343,6 +1469,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
 void amdgpu_acpi_fini(struct amdgpu_device *adev)
 {
 	unregister_acpi_notifier(&adev->acpi_nb);
+	amdgpu_acpi_uma_option_fini();
 }
 
 /**

-- 
2.43.0

On Fri, Nov 14, 2025 at 3:52 AM Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com> wrote:
>
> Add two sysfs files as interfaces to inspect or change UMA carveout
> size. These files are:
>
> - uma_carveout_options: a read-only file listing all the available
>   UMA allocation options and their index.
>
> - uma_carveout: a file that is both readable and writable. On read,
>   it shows the index of the current setting. Writing a valid index
>   into this file allows users to change the UMA carveout size to that
>   option on the next boot.

Would it be cleaner to combine these?  Reading the file would show the
indexed list of options with a * next to the currently selected one
and then writing the index to the file would cause the change to take
effect on the next reboot.

Alex

>
> Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 127 +++++++++++++++++++++++++++++++
>  1 file changed, 127 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 444ab4102168..b9378f34eb79 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -30,6 +30,7 @@
>  #include <linux/power_supply.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/suspend.h>
> +#include <linux/device.h>
>  #include <acpi/video.h>
>  #include <acpi/actbl.h>
>
> @@ -1247,6 +1248,125 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
>         return -ENOENT;
>  }
>
> +static ssize_t uma_carveout_options_show(struct device *dev,
> +                                        struct device_attribute *attr,
> +                                        char *buf)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +       ssize_t size = 0;
> +
> +       if (!uma_info || !uma_info->num_entries)
> +               return -ENODEV;
> +
> +       for (int i = 0; i < uma_info->num_entries; i++) {
> +               size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
> +                                     i,
> +                                     uma_info->entries[i].name,
> +                                     uma_info->entries[i].memory_carved);
> +       }
> +
> +       return size;
> +}
> +static DEVICE_ATTR_RO(uma_carveout_options);
> +
> +static ssize_t uma_carveout_show(struct device *dev,
> +                                struct device_attribute *attr,
> +                                char *buf)
> +{
> +       return sysfs_emit(buf, "%u\n", amdgpu_acpi_priv.atcs.uma_info.uma_option_index);
> +}
> +
> +static ssize_t uma_carveout_store(struct device *dev,
> +                                 struct device_attribute *attr,
> +                                 const char *buf, size_t count)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +       struct drm_device *ddev = dev_get_drvdata(dev);
> +       struct amdgpu_device *adev = drm_to_adev(ddev);
> +       struct amdgpu_uma_carveout_option *opt;
> +       unsigned long val;
> +       uint8_t flags;
> +       int r;
> +
> +       r = kstrtoul(buf, 10, &val);
> +       if (r)
> +               return r;
> +
> +       if (val >= uma_info->num_entries)
> +               return -EINVAL;
> +
> +       opt = &uma_info->entries[val];
> +
> +       if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
> +           !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
> +               drm_err_once(ddev, "Option %ul not supported due to lack of Custom/Auto flag", r);
> +               return -EINVAL;
> +       }
> +
> +       flags = opt->flags;
> +       flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
> +
> +       guard(mutex)(&uma_info->update_lock);
> +
> +       r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
> +       if (r)
> +               return r;
> +
> +       uma_info->uma_option_index = val;
> +
> +       return count;
> +}
> +static DEVICE_ATTR_RW(uma_carveout);
> +
> +static struct attribute *amdgpu_uma_attrs[] = {
> +       &dev_attr_uma_carveout.attr,
> +       &dev_attr_uma_carveout_options.attr,
> +       NULL
> +};
> +
> +const struct attribute_group amdgpu_uma_attr_group = {
> +       .attrs = amdgpu_uma_attrs
> +};
> +
> +static int amdgpu_acpi_uma_option_init(struct amdgpu_device *adev)
> +{
> +       struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
> +       int rc;
> +
> +       if (!atcs->functions.set_uma_allocation_size)
> +               return -ENODEV;
> +
> +       rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &atcs->uma_info);
> +       if (rc) {
> +               drm_dbg(adev_to_drm(adev),
> +                       "Failed to parse UMA carveout info from VBIOS: %d\n", rc);
> +               goto out_info;
> +       }
> +
> +       mutex_init(&atcs->uma_info.update_lock);
> +
> +       rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
> +       if (rc) {
> +               drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs interfaces %d\n", rc);
> +               goto out_attr;
> +       }
> +
> +       return 0;
> +
> +out_attr:
> +       mutex_destroy(&atcs->uma_info.update_lock);
> +out_info:
> +       return rc;
> +}
> +
> +static void amdgpu_acpi_uma_option_fini(void)
> +{
> +       struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +
> +       mutex_destroy(&uma_info->update_lock);
> +       uma_info->num_entries = 0;
> +}
> +
>  /**
>   * amdgpu_acpi_event - handle notify events
>   *
> @@ -1291,6 +1411,12 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
>  int amdgpu_acpi_init(struct amdgpu_device *adev)
>  {
>         struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
> +       int rc;
> +
> +       rc = amdgpu_acpi_uma_option_init(adev);
> +
> +       if (rc)
> +               drm_dbg(adev_to_drm(adev), "Not creating uma carveout interfaces: %d", rc);
>
>         if (atif->notifications.brightness_change) {
>                 if (adev->dc_enabled) {
> @@ -1343,6 +1469,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
>  void amdgpu_acpi_fini(struct amdgpu_device *adev)
>  {
>         unregister_acpi_notifier(&adev->acpi_nb);
> +       amdgpu_acpi_uma_option_fini();
>  }
>
>  /**
>
> --
> 2.43.0
>

On 11/14/2025 2:42 AM, Yo-Jung Leo Lin (AMD) wrote:
> Add two sysfs files as interfaces to inspect or change UMA carveout
> size. These files are:
> 
> - uma_carveout_options: a read-only file listing all the available
>    UMA allocation options and their index.
> 
> - uma_carveout: a file that is both readable and writable. On read,
>    it shows the index of the current setting. Writing a valid index
>    into this file allows users to change the UMA carveout size to that
>    option on the next boot.
> 
> Co-developed-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 127 +++++++++++++++++++++++++++++++
>   1 file changed, 127 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 444ab4102168..b9378f34eb79 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -30,6 +30,7 @@
>   #include <linux/power_supply.h>
>   #include <linux/pm_runtime.h>
>   #include <linux/suspend.h>
> +#include <linux/device.h>
>   #include <acpi/video.h>
>   #include <acpi/actbl.h>
>   
> @@ -1247,6 +1248,125 @@ int amdgpu_acpi_get_mem_info(struct amdgpu_device *adev, int xcc_id,
>   	return -ENOENT;
>   }
>   
> +static ssize_t uma_carveout_options_show(struct device *dev,
> +					 struct device_attribute *attr,
> +					 char *buf)
> +{
> +	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +	ssize_t size = 0;
> +
> +	if (!uma_info || !uma_info->num_entries)
> +		return -ENODEV;
> +
> +	for (int i = 0; i < uma_info->num_entries; i++) {
> +		size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
> +				      i,
> +				      uma_info->entries[i].name,
> +				      uma_info->entries[i].memory_carved);

AFAICT when memory_carved is 0 does this shows as:

0: Minimum (0 GB)

This is actually 512 MB right?

Could you cross reference what Windows shows in that case?  Do they 
special case it to 512 MB?

I'm wondering if maybe that should be special cased here.
> +	}
> +
> +	return size;
> +}
> +static DEVICE_ATTR_RO(uma_carveout_options);
> +
> +static ssize_t uma_carveout_show(struct device *dev,
> +				 struct device_attribute *attr,
> +				 char *buf)
> +{
> +	return sysfs_emit(buf, "%u\n", amdgpu_acpi_priv.atcs.uma_info.uma_option_index);
> +}
> +
> +static ssize_t uma_carveout_store(struct device *dev,
> +				  struct device_attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +	struct drm_device *ddev = dev_get_drvdata(dev);
> +	struct amdgpu_device *adev = drm_to_adev(ddev);
> +	struct amdgpu_uma_carveout_option *opt;
> +	unsigned long val;
> +	uint8_t flags;
> +	int r;
> +
> +	r = kstrtoul(buf, 10, &val);
> +	if (r)
> +		return r;
> +
> +	if (val >= uma_info->num_entries)
> +		return -EINVAL;
> +
> +	opt = &uma_info->entries[val];
> +
> +	if (!(opt->flags & AMDGPU_UMA_FLAG_AUTO) &&
> +	    !(opt->flags & AMDGPU_UMA_FLAG_CUSTOM)) {
> +		drm_err_once(ddev, "Option %ul not supported due to lack of Custom/Auto flag", r);
> +		return -EINVAL;
> +	}
> +
> +	flags = opt->flags;
> +	flags &= ~((flags & AMDGPU_UMA_FLAG_AUTO) >> 1);
> +
> +	guard(mutex)(&uma_info->update_lock);
> +
> +	r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
> +	if (r)
> +		return r;
> +
> +	uma_info->uma_option_index = val;
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(uma_carveout);
> +
> +static struct attribute *amdgpu_uma_attrs[] = {
> +	&dev_attr_uma_carveout.attr,
> +	&dev_attr_uma_carveout_options.attr,
> +	NULL
> +};
> +
> +const struct attribute_group amdgpu_uma_attr_group = {
> +	.attrs = amdgpu_uma_attrs
> +};
> +
> +static int amdgpu_acpi_uma_option_init(struct amdgpu_device *adev)
> +{
> +	struct amdgpu_atcs *atcs = &amdgpu_acpi_priv.atcs;
> +	int rc;
> +
> +	if (!atcs->functions.set_uma_allocation_size)
> +		return -ENODEV;
> +
> +	rc = amdgpu_atomfirmware_get_uma_carveout_info(adev, &atcs->uma_info);
> +	if (rc) {
> +		drm_dbg(adev_to_drm(adev),
> +			"Failed to parse UMA carveout info from VBIOS: %d\n", rc);
> +		goto out_info;
> +	}
> +
> +	mutex_init(&atcs->uma_info.update_lock);
> +
> +	rc = devm_device_add_group(adev->dev, &amdgpu_uma_attr_group);
> +	if (rc) {
> +		drm_dbg(adev_to_drm(adev), "Failed to add UMA carveout sysfs interfaces %d\n", rc);
> +		goto out_attr;
> +	}
> +
> +	return 0;
> +
> +out_attr:
> +	mutex_destroy(&atcs->uma_info.update_lock);
> +out_info:
> +	return rc;
> +}
> +
> +static void amdgpu_acpi_uma_option_fini(void)
> +{
> +	struct amdgpu_uma_carveout_info *uma_info = &amdgpu_acpi_priv.atcs.uma_info;
> +
> +	mutex_destroy(&uma_info->update_lock);
> +	uma_info->num_entries = 0;
> +}
> +
>   /**
>    * amdgpu_acpi_event - handle notify events
>    *
> @@ -1291,6 +1411,12 @@ static int amdgpu_acpi_event(struct notifier_block *nb,
>   int amdgpu_acpi_init(struct amdgpu_device *adev)
>   {
>   	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
> +	int rc;
> +
> +	rc = amdgpu_acpi_uma_option_init(adev);
> +
> +	if (rc)
> +		drm_dbg(adev_to_drm(adev), "Not creating uma carveout interfaces: %d", rc);
>   
>   	if (atif->notifications.brightness_change) {
>   		if (adev->dc_enabled) {
> @@ -1343,6 +1469,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
>   void amdgpu_acpi_fini(struct amdgpu_device *adev)
>   {
>   	unregister_acpi_notifier(&adev->acpi_nb);
> +	amdgpu_acpi_uma_option_fini();
>   }
>   
>   /**
>