hwmon: (smsc47b397) Use request_muxed_region for Super-IO accesses

Super-IO accesses may fail on a system with no or unmapped LPC bus.

Also, other drivers may attempt to access the LPC bus at the same time,
resulting in undefined behavior.

Use request_muxed_region() to ensure that IO access on the requested
address space is supported, and to ensure that access by multiple drivers
is synchronized.

Fixes: 8d5d45fb ("I2C: Move hwmon drivers (2/3)")
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reported-by: John Garry <john.garry@huawei.com>
Cc: John Garry <john.garry@huawei.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/smsc47b397.c

@@ -72,14 +72,19 @@ static inline void superio_select(int ld)
 	superio_outb(0x07, ld);
 }
 
-static inline void superio_enter(void)
+static inline int superio_enter(void)
 {
+	if (!request_muxed_region(REG, 2, DRVNAME))
+		return -EBUSY;
+
 	outb(0x55, REG);
+	return 0;
 }
 
 static inline void superio_exit(void)
 {
 	outb(0xAA, REG);
+	release_region(REG, 2);
 }
 
 #define SUPERIO_REG_DEVID	0x20
@@ -300,8 +305,12 @@ static int __init smsc47b397_find(void)
 	u8 id, rev;
 	char *name;
 	unsigned short addr;
+	int err;
+
+	err = superio_enter();
+	if (err)
+		return err;
 
-	superio_enter();
 	id = force_id ? force_id : superio_inb(SUPERIO_REG_DEVID);
 
 	switch (id) {