Always restore previous bank register after reading/writing data

There is some indication that other entities (BIOS ? EC ?) may access
the chip asynchronously. Restore the bank selection after read/write
operations to limit any potenial impact.

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

diff --git a/it87.c b/it87.c
index 50489971715ec2cfaf3f5d8296c90c5c4d6095d3..e1d3b2ac603ff598e014db9fa86bd27bb734e656 100644 (file)
--- a/it87.c
+++ b/it87.c
@@ -723,7 +723,6 @@ struct it87_data {
        const struct attribute_group *groups[7];
        enum chips type;
        u32 features;
-       u8 bank;
        u8 peci_mask;
        u8 old_peci_mask;
 
@@ -921,16 +920,21 @@ static void _it87_write_value(struct it87_data *data, u8 reg, u8 value)
        outb_p(value, data->addr + IT87_DATA_REG_OFFSET);
 }
 
-static void it87_set_bank(struct it87_data *data, u8 bank)
+static u8 it87_set_bank(struct it87_data *data, u8 bank)
 {
-       if (has_bank_sel(data) && bank != data->bank) {
+       u8 _bank = bank;
+
+       if (has_bank_sel(data)) {
                u8 breg = _it87_read_value(data, IT87_REG_BANK);
 
-               breg &= 0x1f;
-               breg |= (bank << 5);
-               data->bank = bank;
-               _it87_write_value(data, IT87_REG_BANK, breg);
+               _bank = breg >> 5;
+               if (bank != _bank) {
+                       breg &= 0x1f;
+                       breg |= (bank << 5);
+                       _it87_write_value(data, IT87_REG_BANK, breg);
+               }
        }
+       return _bank;
 }
 
 /*
@@ -940,8 +944,14 @@ static void it87_set_bank(struct it87_data *data, u8 bank)
  */
 static int it87_read_value(struct it87_data *data, u16 reg)
 {
-       it87_set_bank(data, reg >> 8);
-       return _it87_read_value(data, reg & 0xff);
+       u8 bank;
+       int val;
+
+       bank = it87_set_bank(data, reg >> 8);
+       val = _it87_read_value(data, reg & 0xff);
+       it87_set_bank(data, bank);
+
+       return val;
 }
 
 /*
@@ -951,8 +961,11 @@ static int it87_read_value(struct it87_data *data, u16 reg)
  */
 static void it87_write_value(struct it87_data *data, u16 reg, u8 value)
 {
-       it87_set_bank(data, reg >> 8);
+       u8 bank;
+
+       bank = it87_set_bank(data, reg >> 8);
        _it87_write_value(data, reg & 0xff, value);
+       it87_set_bank(data, bank);
 }
 
 static void it87_update_pwm_ctrl(struct it87_data *data, int nr)
@@ -3661,7 +3674,6 @@ static int it87_probe(struct platform_device *pdev)
        data->pwm_num_temp_map = it87_devices[sio_data->type].num_temp_map;
        data->peci_mask = it87_devices[sio_data->type].peci_mask;
        data->old_peci_mask = it87_devices[sio_data->type].old_peci_mask;
-       data->bank = 0xff;
 
        /*
         * IT8705F Datasheet 0.4.1, 3h == Version G.