[AMD Official Use Only - AMD Internal Distribution Only]
> -----Original Message-----
> From: Mario Limonciello (AMD) (kernel.org) <[email protected]>
> Sent: Saturday, November 15, 2025 4:26 AM
> To: Lin, Leo <[email protected]>; Deucher, Alexander
> <[email protected]>; Koenig, Christian
> <[email protected]>; David Airlie <[email protected]>; Simona
> Vetter <[email protected]>; Maarten Lankhorst
> <[email protected]>; Maxime Ripard
> <[email protected]>; Thomas Zimmermann <[email protected]>;
> Jonathan Corbet <[email protected]>
> Cc: [email protected]; [email protected]; linux-
> [email protected]; [email protected]; Tsao, Anson
> <[email protected]>
> Subject: Re: [PATCH v2 4/5] drm/amdgpu: add UMA allocation interfaces to
> sysfs
>
>
>
> 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) <[email protected]>
> > Signed-off-by: Mario Limonciello (AMD) <[email protected]>
> > Signed-off-by: Yo-Jung Leo Lin (AMD) <[email protected]>
> > ---
> > 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?
Yes, this option is actually 512MB. BIOS menu also shows it that way. Will make
it show 512MB in the next version.
BR,
Leo
>
> 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();
> > }
> >
> > /**
> >
