linux-kernel - [PATCH 4/5] drm/amdgpu: add UMA allocation interfaces to sysfs

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Message-ID: <20251103-vram-carveout-tuning-for-upstream-v1-4-17e2a72639c5@amd.com>
Date: Mon, 3 Nov 2025 15:51:07 +0800
From: "Yo-Jung Leo Lin (AMD)" <Leo.Lin@....com>
To: 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>, "Yo-Jung Leo Lin
 (AMD)" <Leo.Lin@....com>, <anson.tsao@....com>, <superm1@...nel.org>
Subject: [PATCH 4/5] drm/amdgpu: add UMA allocation interfaces to sysfs

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@...nel.org>
Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>
Signed-off-by: Yo-Jung Leo Lin (AMD) <Leo.Lin@....com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 95 +++++++++++++++++++++++++++-
 1 file changed, 93 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
index 58cc3bc9d42d..1ebfd925b761 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
@@ -1855,11 +1855,102 @@ const struct attribute_group amdgpu_vbios_version_attr_group = {
 	.is_visible = amdgpu_vbios_version_attrs_is_visible,
 };
 
+static ssize_t uma_carveout_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	struct atom_context *ctx = adev->mode_info.atom_context;
+
+	return sysfs_emit(buf, "%u\n", ctx->uma_carveout_index);
+}
+static ssize_t uma_carveout_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	struct atom_context *ctx = adev->mode_info.atom_context;
+	struct uma_carveout_option *opt;
+	unsigned long val;
+	uint8_t flags;
+	int r;
+
+	r = kstrtoul(buf, 10, &val);
+	if (r)
+		return r;
+
+	if (val >= ctx->uma_carveout_nr)
+		return -EINVAL;
+
+	opt = &ctx->uma_carveout_options[val];
+
+	if (!opt->uma_carveout_option_flags.flags.Auto &&
+	    !opt->uma_carveout_option_flags.flags.Custom) {
+		drm_err_once(ddev, "Option %ul not supported due to lack of Custom/Auto flag", r);
+		return -EINVAL;
+	}
+
+	flags = opt->uma_carveout_option_flags.all8;
+	flags &= ~((uint8_t)opt->uma_carveout_option_flags.flags.Custom);
+
+	r = amdgpu_acpi_set_uma_allocation_size(adev, val, flags);
+	if (r)
+		return r;
+	ctx->uma_carveout_index = val;
+
+	return count;
+}
+static DEVICE_ATTR_RW(uma_carveout);
+
+static ssize_t uma_carveout_options_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+	struct amdgpu_device *adev = drm_to_adev(ddev);
+	struct atom_context *ctx = adev->mode_info.atom_context;
+	ssize_t size = 0;
+
+	for (int i = 0; i < ctx->uma_carveout_nr; i++) {
+		size += sysfs_emit_at(buf, size, "%d: %s (%u GB)\n",
+				      i,
+				      ctx->uma_carveout_options[i].optionName,
+				      ctx->uma_carveout_options[i].memoryCarvedGb);
+	}
+
+	return size;
+}
+static DEVICE_ATTR_RO(uma_carveout_options);
+
+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
+};
+
 int amdgpu_atombios_sysfs_init(struct amdgpu_device *adev)
 {
-	if (adev->mode_info.atom_context)
-		return devm_device_add_group(adev->dev,
+	int r;
+
+	if (adev->mode_info.atom_context) {
+		r = devm_device_add_group(adev->dev,
 					     &amdgpu_vbios_version_attr_group);
+		if (r)
+			return r;
+	}
+	if (adev->mode_info.atom_context->uma_carveout_options &&
+	    adev->mode_info.atom_context->uma_carveout_nr) {
+		r = devm_device_add_group(adev->dev,
+					   &amdgpu_uma_attr_group);
+		if (r)
+			return r;
+	}
 
 	return 0;
 }

-- 
2.43.0