Save and restore bank around envmon register accesses if needed

If an external EC accesses the chip through SMBus registers
and if the chip's environmental registers are paged, it is likely
that the EC modifies the page register. If so, it likely will not
update the page on each access but assume that it "owns" the chip.
If the driver then modifies the page register, subsequent accesses
from the EC will likely have unpredictable results.
To avoid that problem, let's save the page register value after
disabling SMBus accesses and restore the original value when done.
This is only necessary if accesses are not handled through MMIO
since we don't touch the page register in that case.

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

diff --git a/it87.c b/it87.c
index d82bd5fcbc2b8f94c62d36f269d369ea6ad3b871..ce908e396a29d864e1c3c3c4b294c31bcbb175e8 100644 (file)
--- a/it87.c
+++ b/it87.c
@@ -772,6 +772,7 @@ struct it87_data {
        u8 old_peci_mask;
 
        u8 smbus_bitmap;        /* !=0 if SMBus needs to be disabled */
+       u8 saved_bank;          /* saved bank register value */
        u8 ec_special_config;   /* EC special config register restore value */
        u8 sioaddr;             /* SIO port address */
        bool doexit;            /* true if exit from sio config is ok */
@@ -962,6 +963,18 @@ static const unsigned int pwm_freq[8] = {
        750000,
 };
 
+static int _it87_io_read(struct it87_data *data, u16 reg)
+{
+       outb_p(reg, data->addr + IT87_ADDR_REG_OFFSET);
+       return inb_p(data->addr + IT87_DATA_REG_OFFSET);
+}
+
+static void _it87_io_write(struct it87_data *data, u16 reg, u8 value)
+{
+       outb_p(reg, data->addr + IT87_ADDR_REG_OFFSET);
+       outb_p(value, data->addr + IT87_DATA_REG_OFFSET);
+}
+
 static int smbus_disable(struct it87_data *data)
 {
        int err;
@@ -974,6 +987,8 @@ static int smbus_disable(struct it87_data *data)
                superio_outb(data->sioaddr, IT87_SPECIAL_CFG_REG,
                             data->ec_special_config & ~data->smbus_bitmap);
                superio_exit(data->sioaddr, data->doexit);
+               if (has_bank_sel(data) && !data->mmio)
+                       data->saved_bank = _it87_io_read(data, IT87_REG_BANK);
        }
        return 0;
 }
@@ -983,6 +998,8 @@ static int smbus_enable(struct it87_data *data)
        int err;
 
        if (data->smbus_bitmap) {
+               if (has_bank_sel(data) && !data->mmio)
+                       _it87_io_write(data, IT87_REG_BANK, data->saved_bank);
                err = superio_enter(data->sioaddr);
                if (err)
                        return err;
@@ -995,18 +1012,6 @@ static int smbus_enable(struct it87_data *data)
        return 0;
 }
 
-static int _it87_io_read(struct it87_data *data, u16 reg)
-{
-       outb_p(reg, data->addr + IT87_ADDR_REG_OFFSET);
-       return inb_p(data->addr + IT87_DATA_REG_OFFSET);
-}
-
-static void _it87_io_write(struct it87_data *data, u16 reg, u8 value)
-{
-       outb_p(reg, data->addr + IT87_ADDR_REG_OFFSET);
-       outb_p(value, data->addr + IT87_DATA_REG_OFFSET);
-}
-
 static u8 it87_io_set_bank(struct it87_data *data, u8 bank)
 {
        u8 _bank = bank;