[PATCH v4 7/9] hwmon: (dell-smm) Add support for WMI SMM interface

From: Armin Wolf
Date: Wed Nov 22 2023 - 19:49:52 EST

Some Dell machines like the Dell Optiplex 7000 do not support
the legacy SMM interface, but instead expect all SMM calls
to be issued over a special WMI interface.
Add support for this interface so users can control the fans
on those machines.

Tested-by: <serverror@xxxxxxxxxxxxx>
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
drivers/hwmon/Kconfig | 1 +
drivers/hwmon/dell-smm-hwmon.c | 199 +++++++++++++++++++++++++++++----
drivers/platform/x86/wmi.c | 1 +
3 files changed, 182 insertions(+), 19 deletions(-)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index cf27523eed5a..76cb05db1dcf 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -512,6 +512,7 @@ config SENSORS_DS1621

config SENSORS_DELL_SMM
tristate "Dell laptop SMM BIOS hwmon driver"
+ depends on ACPI_WMI
depends on X86
imply THERMAL
help
diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index a377cd08355f..95330437c5af 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -12,6 +12,7 @@

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/acpi.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/ctype.h>
@@ -34,8 +35,10 @@
#include <linux/thermal.h>
#include <linux/types.h>
#include <linux/uaccess.h>
+#include <linux/wmi.h>

#include <linux/i8k.h>
+#include <asm/unaligned.h>

#define I8K_SMM_FN_STATUS 0x0025
#define I8K_SMM_POWER_STATUS 0x0069
@@ -66,6 +69,9 @@
#define I8K_POWER_AC 0x05
#define I8K_POWER_BATTERY 0x01

+#define DELL_SMM_WMI_GUID "F1DDEE52-063C-4784-A11E-8A06684B9B01"
+#define DELL_SMM_LEGACY_EXECUTE 0x1
+
#define DELL_SMM_NO_TEMP 10
#define DELL_SMM_NO_FANS 3

@@ -219,6 +225,103 @@ static const struct dell_smm_ops i8k_smm_ops = {
.smm_call = i8k_smm_call,
};

+/*
+ * Call the System Management Mode BIOS over WMI.
+ */
+static ssize_t wmi_parse_register(u8 *buffer, u32 length, unsigned int *reg)
+{
+ __le32 value;
+ u32 reg_size;
+
+ if (length <= sizeof(reg_size))
+ return -ENODATA;
+
+ reg_size = get_unaligned_le32(buffer);
+ if (!reg_size || reg_size > sizeof(value))
+ return -ENOMSG;
+
+ if (length < sizeof(reg_size) + reg_size)
+ return -ENODATA;
+
+ memcpy_and_pad(&value, sizeof(value), buffer + sizeof(reg_size), reg_size, 0);
+ *reg = le32_to_cpu(value);
+
+ return reg_size + sizeof(reg_size);
+}
+
+static int wmi_parse_response(u8 *buffer, u32 length, struct smm_regs *regs)
+{
+ unsigned int *registers[] = {
+ &regs->eax,
+ &regs->ebx,
+ &regs->ecx,
+ &regs->edx
+ };
+ u32 offset = 0;
+ ssize_t ret;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(registers); i++) {
+ if (offset >= length)
+ return -ENODATA;
+
+ ret = wmi_parse_register(buffer + offset, length - offset, registers[i]);
+ if (ret < 0)
+ return ret;
+
+ offset += ret;
+ }
+
+ if (offset != length)
+ return -ENOMSG;
+
+ return 0;
+}
+
+static int wmi_smm_call(struct device *dev, struct smm_regs *regs)
+{
+ struct wmi_device *wdev = container_of(dev, struct wmi_device, dev);
+ struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
+ u32 wmi_payload[] = {
+ sizeof(regs->eax),
+ regs->eax,
+ sizeof(regs->ebx),
+ regs->ebx,
+ sizeof(regs->ecx),
+ regs->ecx,
+ sizeof(regs->edx),
+ regs->edx
+ };
+ const struct acpi_buffer in = {
+ .length = sizeof(wmi_payload),
+ .pointer = &wmi_payload,
+ };
+ union acpi_object *obj;
+ acpi_status status;
+ int ret;
+
+ status = wmidev_evaluate_method(wdev, 0x0, DELL_SMM_LEGACY_EXECUTE, &in, &out);
+ if (ACPI_FAILURE(status))
+ return -EIO;
+
+ obj = out.pointer;
+ if (!obj)
+ return -ENODATA;
+
+ if (obj->type != ACPI_TYPE_BUFFER) {
+ ret = -ENOMSG;
+
+ goto err_free;
+ }
+
+ ret = wmi_parse_response(obj->buffer.pointer, obj->buffer.length, regs);
+
+err_free:
+ kfree(obj);
+
+ return ret;
+}
+
static int dell_smm_call(const struct dell_smm_ops *ops, struct smm_regs *regs)
{
unsigned int eax = regs->eax;
@@ -306,7 +409,7 @@ static int i8k_get_fan_type(struct dell_smm_data *data, u8 fan)
/*
* Read the fan nominal rpm for specific fan speed.
*/
-static int __init i8k_get_fan_nominal_speed(const struct dell_smm_data *data, u8 fan, int speed)
+static int i8k_get_fan_nominal_speed(const struct dell_smm_data *data, u8 fan, int speed)
{
struct smm_regs regs = {
.eax = I8K_SMM_GET_NOM_SPEED,
@@ -349,7 +452,7 @@ static int i8k_set_fan(const struct dell_smm_data *data, u8 fan, int speed)
return dell_smm_call(data->ops, &regs);
}

-static int __init i8k_get_temp_type(const struct dell_smm_data *data, u8 sensor)
+static int i8k_get_temp_type(const struct dell_smm_data *data, u8 sensor)
{
struct smm_regs regs = {
.eax = I8K_SMM_GET_TEMP_TYPE,
@@ -401,7 +504,7 @@ static int i8k_get_temp(const struct dell_smm_data *data, u8 sensor)
return temp;
}

-static int __init dell_smm_get_signature(const struct dell_smm_ops *ops, int req_fn)
+static int dell_smm_get_signature(const struct dell_smm_ops *ops, int req_fn)
{
struct smm_regs regs = { .eax = req_fn, };
int rc;
@@ -986,7 +1089,7 @@ static const struct hwmon_chip_info dell_smm_chip_info = {
.info = dell_smm_info,
};

-static int __init dell_smm_init_cdev(struct device *dev, u8 fan_num)
+static int dell_smm_init_cdev(struct device *dev, u8 fan_num)
{
struct dell_smm_data *data = dev_get_drvdata(dev);
struct thermal_cooling_device *cdev;
@@ -1017,7 +1120,7 @@ static int __init dell_smm_init_cdev(struct device *dev, u8 fan_num)
return ret;
}

-static int __init dell_smm_init_hwmon(struct device *dev)
+static int dell_smm_init_hwmon(struct device *dev)
{
struct dell_smm_data *data = dev_get_drvdata(dev);
struct device *dell_smm_hwmon_dev;
@@ -1083,7 +1186,7 @@ static int __init dell_smm_init_hwmon(struct device *dev)
return PTR_ERR_OR_ZERO(dell_smm_hwmon_dev);
}

-static int __init dell_smm_init_data(struct device *dev, const struct dell_smm_ops *ops)
+static int dell_smm_init_data(struct device *dev, const struct dell_smm_ops *ops)
{
struct dell_smm_data *data;

@@ -1409,6 +1512,9 @@ static const struct dmi_system_id i8k_whitelist_fan_control[] __initconst = {
{ }
};

+/*
+ * Legacy SMM backend driver.
+ */
static int __init dell_smm_probe(struct platform_device *pdev)
{
int ret;
@@ -1434,6 +1540,47 @@ static struct platform_driver dell_smm_driver = {

static struct platform_device *dell_smm_device;

+/*
+ * WMI SMM backend driver.
+ */
+static int dell_smm_wmi_probe(struct wmi_device *wdev, const void *context)
+{
+ struct dell_smm_ops *ops;
+ int ret;
+
+ ops = devm_kzalloc(&wdev->dev, sizeof(*ops), GFP_KERNEL);
+ if (!ops)
+ return -ENOMEM;
+
+ ops->smm_call = wmi_smm_call;
+ ops->smm_dev = &wdev->dev;
+
+ if (dell_smm_get_signature(ops, I8K_SMM_GET_DELL_SIG1) &&
+ dell_smm_get_signature(ops, I8K_SMM_GET_DELL_SIG2))
+ return -ENODEV;
+
+ ret = dell_smm_init_data(&wdev->dev, ops);
+ if (ret < 0)
+ return ret;
+
+ return dell_smm_init_hwmon(&wdev->dev);
+}
+
+static const struct wmi_device_id dell_smm_wmi_id_table[] = {
+ { DELL_SMM_WMI_GUID, NULL },
+ { }
+};
+MODULE_DEVICE_TABLE(wmi, dell_smm_wmi_id_table);
+
+static struct wmi_driver dell_smm_wmi_driver = {
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+ },
+ .id_table = dell_smm_wmi_id_table,
+ .probe = dell_smm_wmi_probe,
+};
+
/*
* Probe for the presence of a supported laptop.
*/
@@ -1485,33 +1632,43 @@ static void __init dell_smm_init_dmi(void)
}
}

-static int __init i8k_init(void)
+static int __init dell_smm_legacy_check(void)
{
- /*
- * Get DMI information
- */
if (!dmi_check_system(i8k_dmi_table)) {
if (!ignore_dmi && !force)
return -ENODEV;

- pr_info("not running on a supported Dell system.\n");
+ pr_info("Probing for legacy SMM handler on unsupported machine\n");
pr_info("vendor=%s, model=%s, version=%s\n",
i8k_get_dmi_data(DMI_SYS_VENDOR),
i8k_get_dmi_data(DMI_PRODUCT_NAME),
i8k_get_dmi_data(DMI_BIOS_VERSION));
}

- dell_smm_init_dmi();
-
- /*
- * Get SMM Dell signature
- */
if (dell_smm_get_signature(&i8k_smm_ops, I8K_SMM_GET_DELL_SIG1) &&
dell_smm_get_signature(&i8k_smm_ops, I8K_SMM_GET_DELL_SIG2)) {
if (!force)
return -ENODEV;

- pr_err("Unable to get Dell SMM signature\n");
+ pr_warn("Forcing legacy SMM calls on a possibly incompatible machine\n");
+ }
+
+ return 0;
+}
+
+static int __init i8k_init(void)
+{
+ int ret;
+
+ dell_smm_init_dmi();
+
+ ret = dell_smm_legacy_check();
+ if (ret < 0) {
+ /*
+ * On modern machines, SMM communication happens over WMI, meaning
+ * the SMM handler might not react to legacy SMM calls.
+ */
+ return wmi_driver_register(&dell_smm_wmi_driver);
}

dell_smm_device = platform_create_bundle(&dell_smm_driver, dell_smm_probe, NULL, 0, NULL,
@@ -1522,8 +1679,12 @@ static int __init i8k_init(void)

static void __exit i8k_exit(void)
{
- platform_device_unregister(dell_smm_device);
- platform_driver_unregister(&dell_smm_driver);
+ if (dell_smm_device) {
+ platform_device_unregister(dell_smm_device);
+ platform_driver_unregister(&dell_smm_driver);
+ } else {
+ wmi_driver_unregister(&dell_smm_wmi_driver);
+ }
}

module_init(i8k_init);
diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index 5c27b4aa9690..d68a96a2c570 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -106,6 +106,7 @@ MODULE_DEVICE_TABLE(acpi, wmi_device_ids);
static const char * const allow_duplicates[] = {
"05901221-D566-11D1-B2F0-00A0C9062910", /* wmi-bmof */
"8A42EA14-4F2A-FD45-6422-0087F7A7E608", /* dell-wmi-ddv */
+ "F1DDEE52-063C-4784-A11E-8A06684B9B01", /* dell-smm-hwmon */
NULL
};

--
2.39.2