platform/x86/amd: amd_3d_vcache: Add AMD 3D V-Cache optimizer driver

AMD X3D processors, also known as AMD 3D V-Cache, feature dual Core
Complex Dies (CCDs) and enlarged L3 cache, enabling dynamic mode
switching between Frequency and Cache modes. To optimize performance,
implement the AMD 3D V-Cache Optimizer, which allows selecting either:

Frequency mode: cores within the faster CCD are prioritized before
those in the slower CCD.

Cache mode: cores within the larger L3 CCD are prioritized before
those in the smaller L3 CCD.

Co-developed-by: Perry Yuan <[e-mail]>
Signed-off-by: Perry Yuan <[e-mail]>
Co-developed-by: Mario Limonciello <[e-mail]>
Signed-off-by: Mario Limonciello <[e-mail]>
Reviewed-by: Shyam Sundar S K <[e-mail]>
Reviewed-by: Armin Wolf <[e-mail]>
Signed-off-by: Basavaraj Natikar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Ilpo Järvinen <[e-mail]>
Signed-off-by: Ilpo Järvinen <[e-mail]>

MAINTAINERS

···
 F:	drivers/infiniband/hw/efa/
 F:	include/uapi/rdma/efa-abi.h
 
+AMD 3D V-CACHE PERFORMANCE OPTIMIZER DRIVER
+M:	Basavaraj Natikar <[e-mail]>
+R:	Mario Limonciello <[e-mail]>
+L:	[e-mail]
+S:	Supported
+F:	drivers/platform/x86/amd/x3d_vcache.c
+
 AMD ADDRESS TRANSLATION LIBRARY (ATL)
 M:	Yazen Ghannam <[e-mail]>
 L:	[e-mail]

drivers/platform/x86/amd/Kconfig

···
 source "drivers/platform/x86/amd/pmf/Kconfig"
 source "drivers/platform/x86/amd/pmc/Kconfig"
 
+config AMD_3D_VCACHE
+	tristate "AMD 3D V-Cache Performance Optimizer Driver"
+	depends on X86_64 && ACPI
+	help
+	  The driver provides a sysfs interface, enabling the setting of a bias
+	  that alters CPU core reordering. This bias prefers cores with higher
+	  frequencies or larger L3 caches on processors supporting AMD 3D V-Cache
+	  technology.
+
+	  If you choose to compile this driver as a module the module will be
+	  called amd_3d_vcache.
+
 config AMD_WBRF
 	bool "AMD Wifi RF Band mitigations (WBRF)"
 	depends on ACPI

drivers/platform/x86/amd/Makefile

···
 # AMD x86 Platform-Specific Drivers
 #
 
+obj-$(CONFIG_AMD_3D_VCACHE)	+= amd_3d_vcache.o
+amd_3d_vcache-objs		:= x3d_vcache.o
 obj-$(CONFIG_AMD_PMC)		+= pmc/
 obj-$(CONFIG_AMD_HSMP)		+= hsmp/
 obj-$(CONFIG_AMD_PMF)		+= pmf/

drivers/platform/x86/amd/x3d_vcache.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AMD 3D V-Cache Performance Optimizer Driver
+ *
+ * Copyright (c) 2024, Advanced Micro Devices, Inc.
+ * All Rights Reserved.
+ *
+ * Authors: Basavaraj Natikar <[e-mail]>
+ *          Perry Yuan <[e-mail]>
+ *          Mario Limonciello <[e-mail]>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/array_size.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/sysfs.h>
+#include <linux/uuid.h>
+
+static char *x3d_mode = "frequency";
+module_param(x3d_mode, charp, 0);
+MODULE_PARM_DESC(x3d_mode, "Initial 3D-VCache mode; 'frequency' (default) or 'cache'");
+
+#define DSM_REVISION_ID			0
+#define DSM_SET_X3D_MODE		1
+
+static guid_t x3d_guid = GUID_INIT(0xdff8e55f, 0xbcfd, 0x46fb, 0xba, 0x0a,
+				   0xef, 0xd0, 0x45, 0x0f, 0x34, 0xee);
+
+enum amd_x3d_mode_type {
+	MODE_INDEX_FREQ,
+	MODE_INDEX_CACHE,
+};
+
+static const char * const amd_x3d_mode_strings[] = {
+	[MODE_INDEX_FREQ] = "frequency",
+	[MODE_INDEX_CACHE] = "cache",
+};
+
+struct amd_x3d_dev {
+	struct device *dev;
+	acpi_handle ahandle;
+	/* To protect x3d mode setting */
+	struct mutex lock;
+	enum amd_x3d_mode_type curr_mode;
+};
+
+static int amd_x3d_get_mode(struct amd_x3d_dev *data)
+{
+	guard(mutex)(&data->lock);
+
+	return data->curr_mode;
+}
+
+static int amd_x3d_mode_switch(struct amd_x3d_dev *data, int new_state)
+{
+	union acpi_object *out, argv;
+
+	guard(mutex)(&data->lock);
+	argv.type = ACPI_TYPE_INTEGER;
+	argv.integer.value = new_state;
+
+	out = acpi_evaluate_dsm(data->ahandle, &x3d_guid, DSM_REVISION_ID,
+				DSM_SET_X3D_MODE, &argv);
+	if (!out) {
+		dev_err(data->dev, "failed to evaluate _DSM\n");
+		return -EINVAL;
+	}
+
+	data->curr_mode = new_state;
+
+	kfree(out);
+
+	return 0;
+}
+
+static ssize_t amd_x3d_mode_store(struct device *dev, struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct amd_x3d_dev *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = sysfs_match_string(amd_x3d_mode_strings, buf);
+	if (ret < 0)
+		return ret;
+
+	ret = amd_x3d_mode_switch(data, ret);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static ssize_t amd_x3d_mode_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct amd_x3d_dev *data = dev_get_drvdata(dev);
+	int mode = amd_x3d_get_mode(data);
+
+	return sysfs_emit(buf, "%s\n", amd_x3d_mode_strings[mode]);
+}
+static DEVICE_ATTR_RW(amd_x3d_mode);
+
+static struct attribute *amd_x3d_attrs[] = {
+	&dev_attr_amd_x3d_mode.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(amd_x3d);
+
+static int amd_x3d_resume_handler(struct device *dev)
+{
+	struct amd_x3d_dev *data = dev_get_drvdata(dev);
+	int ret = amd_x3d_get_mode(data);
+
+	return amd_x3d_mode_switch(data, ret);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(amd_x3d_pm, NULL, amd_x3d_resume_handler);
+
+static const struct acpi_device_id amd_x3d_acpi_ids[] = {
+	{"AMDI0101"},
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, amd_x3d_acpi_ids);
+
+static int amd_x3d_probe(struct platform_device *pdev)
+{
+	struct amd_x3d_dev *data;
+	acpi_handle handle;
+	int ret;
+
+	handle = ACPI_HANDLE(&pdev->dev);
+	if (!handle)
+		return -ENODEV;
+
+	if (!acpi_check_dsm(handle, &x3d_guid, DSM_REVISION_ID, BIT(DSM_SET_X3D_MODE)))
+		return -ENODEV;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->dev = &pdev->dev;
+
+	ret = devm_mutex_init(data->dev, &data->lock);
+	if (ret)
+		return ret;
+
+	data->ahandle = handle;
+	platform_set_drvdata(pdev, data);
+
+	ret = match_string(amd_x3d_mode_strings, ARRAY_SIZE(amd_x3d_mode_strings), x3d_mode);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, -EINVAL, "invalid mode %s\n", x3d_mode);
+
+	return amd_x3d_mode_switch(data, ret);
+}
+
+static struct platform_driver amd_3d_vcache_driver = {
+	.driver = {
+		.name = "amd_x3d_vcache",
+		.dev_groups = amd_x3d_groups,
+		.acpi_match_table = amd_x3d_acpi_ids,
+		.pm = pm_sleep_ptr(&amd_x3d_pm),
+	},
+	.probe = amd_x3d_probe,
+};
+module_platform_driver(amd_3d_vcache_driver);
+
+MODULE_DESCRIPTION("AMD 3D V-Cache Performance Optimizer Driver");
+MODULE_LICENSE("GPL");