[PATCH v2 2/3] hwmon: (nct6775) Implement custom lock by ACPI mutex

Denis Pauk
2021-11-28T18:48:20Z

Use ACPI lock when the board has a separate lock for monitoring IO.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204807
Signed-off-by: Denis Pauk <pauk.denis@gmail.com>

---
Changes in v2:
- Fix commit message.
- Use an anonymous union for mutexes.
- Use temporary status varibale in acpi calls.
---
drivers/hwmon/nct6775.c | 59 +++++++++++++++++++++++++++++++++--------
1 file changed, 48 insertions(+), 11 deletions(-)

diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
index 049c42ea66bb..206c20a1ae9b 100644
--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -140,6 +140,7 @@ struct nct6775_sio_data {
int ld;
enum kinds kind;
enum sensor_access access;
+ acpi_handle acpi_wmi_mutex;

/* superio_() callbacks */
void (*sio_outb)(struct nct6775_sio_data *sio_data, int reg, int val);
@@ -155,6 +156,8 @@ struct nct6775_sio_data {
#define ASUSWMI_METHODID_RHWM 0x5248574D
#define ASUSWMI_METHODID_WHWM 0x5748574D
#define ASUSWMI_UNSUPPORTED_METHOD 0xFFFFFFFE
+/* Wait for up to 0.5 s to acquire the lock */
+#define ASUSWMI_LOCK_TIMEOUT_MS 500

static int nct6775_asuswmi_evaluate_method(u32 method_id, u8 bank, u8 reg, u8 val, u32 *retval)
{
@@ -1243,7 +1246,11 @@ struct nct6775_data {
unsigned int (*fan_from_reg)(u16 reg, unsigned int divreg);
unsigned int (*fan_from_reg_min)(u16 reg, unsigned int divreg);

- struct mutex update_lock;
+ union {
+ struct mutex update_lock; /* non ACPI lock */
+ acpi_handle acpi_wmi_mutex; /* ACPI lock */
+ } mlock;
+
bool valid; /* true if following fields are valid */
unsigned long last_updated; /* In jiffies */

@@ -1563,6 +1570,26 @@ static int nct6775_wmi_write_value(struct nct6775_data *data, u16 reg, u16 value
return res;
}

+static int nct6775_wmi_lock(struct nct6775_data *data)
+{
+ acpi_status status;
+
+ status = acpi_acquire_mutex(data->mlock.acpi_wmi_mutex, NULL, ASUSWMI_LOCK_TIMEOUT_MS);
+ if (ACPI_FAILURE(status))
+ return -EIO;
+
+ return 0;
+}
+
+static void nct6775_wmi_unlock(struct nct6775_data *data, struct device *dev)
+{
+ acpi_status status;
+
+ status = acpi_release_mutex(data->mlock.acpi_wmi_mutex, NULL);
+ if (ACPI_FAILURE(status))
+ dev_err(dev, "Failed to release mutex.");
+}
+
/*
* On older chips, only registers 0x50-0x5f are banked.
* On more recent chips, all registers are banked.
@@ -1922,14 +1949,14 @@ static void nct6775_update_pwm_limits(struct device *dev)

static int nct6775_lock(struct nct6775_data *data)
{
- mutex_lock(&data->update_lock);
+ mutex_lock(&data->mlock.update_lock);

return 0;
}

static void nct6775_unlock(struct nct6775_data *data, struct device *dev)
{
- mutex_unlock(&data->update_lock);
+ mutex_unlock(&data->mlock.update_lock);
}

static struct nct6775_data *nct6775_update_device(struct device *dev)
@@ -4061,9 +4088,15 @@ static int nct6775_probe(struct platform_device *pdev)
data->write_value = nct6775_wmi_write_value;
}

- mutex_init(&data->update_lock);
- data->lock = nct6775_lock;
- data->unlock = nct6775_unlock;
+ if (sio_data->acpi_wmi_mutex) {
+ data->mlock.acpi_wmi_mutex = sio_data->acpi_wmi_mutex;
+ data->lock = nct6775_wmi_lock;
+ data->unlock = nct6775_wmi_unlock;
+ } else {
+ mutex_init(&data->mlock.update_lock);
+ data->lock = nct6775_lock;
+ data->unlock = nct6775_unlock;
+ }

data->name = nct6775_device_names[data->kind];
data->bank = 0xff; /* Force initial bank selection */
@@ -5114,6 +5147,7 @@ static int __init sensors_nct6775_init(void)
int sioaddr[2] = { 0x2e, 0x4e };
enum sensor_access access = access_direct;
const char *board_vendor, *board_name;
+ acpi_handle acpi_wmi_mutex = NULL;
u8 tmp;

err = platform_driver_register(&nct6775_driver);
@@ -5159,6 +5193,7 @@ static int __init sensors_nct6775_init(void)
found = true;

sio_data.access = access;
+ sio_data.acpi_wmi_mutex = acpi_wmi_mutex;

if (access == access_asuswmi) {
sio_data.sio_outb = superio_wmi_outb;
@@ -5186,11 +5221,13 @@ static int __init sensors_nct6775_init(void)
res.end = address + IOREGION_OFFSET + IOREGION_LENGTH - 1;
res.flags = IORESOURCE_IO;

- err = acpi_check_resource_conflict(&res);
- if (err) {
- platform_device_put(pdev[i]);
- pdev[i] = NULL;
- continue;
+ if (!acpi_wmi_mutex) {
+ err = acpi_check_resource_conflict(&res);
+ if (err) {
+ platform_device_put(pdev[i]);
+ pdev[i] = NULL;
+ continue;
+ }
}

err = platform_device_add_resources(pdev[i], &res, 1);
--
2.33.0