hwmon: (nct6775) Restore hardware monitoring logical device status on resume

After a suspend/resume cycle it is not guaranteed that the hardware monitoring
device is still enabled. Ensure that this is the case after resume.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 22 insertions, 13 deletions

diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
index db6a68efc389..0445a52379e7 100644
--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -885,6 +885,7 @@ struct nct6775_data {
         u8 vbat;
         u8 fandiv1;
         u8 fandiv2;
+        u8 sio_reg_enable;
 };
 
 struct nct6775_sio_data {
@@ -3177,6 +3178,10 @@ nct6775_check_fan_inputs(struct nct6775_data *data)
         int sioreg = data->sioreg;
         int regval;
 
+        /* Store SIO_REG_ENABLE for use during resume */
+        superio_select(sioreg, NCT6775_LD_HWM);
+        data->sio_reg_enable = superio_inb(sioreg, SIO_REG_ENABLE);
+
         /* fan4 and fan5 share some pins with the GPIO and serial flash */
         if (data->kind == nct6775) {
                 regval = superio_inb(sioreg, 0x2c);
@@ -3195,20 +3200,17 @@ nct6775_check_fan_inputs(struct nct6775_data *data)
         } else if (data->kind == nct6776) {
                 bool gpok = superio_inb(sioreg, 0x27) & 0x80;
 
-                superio_select(sioreg, NCT6775_LD_HWM);
-                regval = superio_inb(sioreg, SIO_REG_ENABLE);
-
-                if (regval & 0x80)
+                if (data->sio_reg_enable & 0x80)
                         fan3pin = gpok;
                 else
                         fan3pin = !(superio_inb(sioreg, 0x24) & 0x40);
 
-                if (regval & 0x40)
+                if (data->sio_reg_enable & 0x40)
                         fan4pin = gpok;
                 else
                         fan4pin = superio_inb(sioreg, 0x1C) & 0x01;
 
-                if (regval & 0x20)
+                if (data->sio_reg_enable & 0x20)
                         fan5pin = gpok;
                 else
                         fan5pin = superio_inb(sioreg, 0x1C) & 0x02;
@@ -4006,19 +4008,26 @@ static int __maybe_unused nct6775_suspend(struct device *dev)
 static int __maybe_unused nct6775_resume(struct device *dev)
 {
         struct nct6775_data *data = dev_get_drvdata(dev);
+        int sioreg = data->sioreg;
         int i, j, err = 0;
+        u8 reg;
 
         mutex_lock(&data->update_lock);
         data->bank = 0xff;              /* Force initial bank selection */
 
-        if (data->kind == nct6791 || data->kind == nct6792) {
-                err = superio_enter(data->sioreg);
-                if (err)
-                        goto abort;
+        err = superio_enter(sioreg);
+        if (err)
+                goto abort;
 
-                nct6791_enable_io_mapping(data->sioreg);
-                superio_exit(data->sioreg);
-        }
+        superio_select(sioreg, NCT6775_LD_HWM);
+        reg = superio_inb(sioreg, SIO_REG_ENABLE);
+        if (reg != data->sio_reg_enable)
+                superio_outb(sioreg, SIO_REG_ENABLE, data->sio_reg_enable);
+
+        if (data->kind == nct6791 || data->kind == nct6792)
+                nct6791_enable_io_mapping(sioreg);
+
+        superio_exit(sioreg);
 
         /* Restore limits */
         for (i = 0; i < data->in_num; i++) {