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Subject[PATCH 4.19 158/276] hwmon: (smsc47m1) Use request_muxed_region for Super-IO accesses
Date
[ Upstream commit d6410408ad2a798c4cc685252c1baa713be0ad69 ]

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: 8d5d45fb1468 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hwmon/smsc47m1.c | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
index c7b6a425e2c02..5eeac9853d0ae 100644
--- a/drivers/hwmon/smsc47m1.c
+++ b/drivers/hwmon/smsc47m1.c
@@ -73,16 +73,21 @@ superio_inb(int reg)
/* logical device for fans is 0x0A */
#define superio_select() superio_outb(0x07, 0x0A)

-static inline 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_ACT 0x30
@@ -531,8 +536,12 @@ static int __init smsc47m1_find(struct smsc47m1_sio_data *sio_data)
{
u8 val;
unsigned short addr;
+ int err;
+
+ err = superio_enter();
+ if (err)
+ return err;

- superio_enter();
val = force_id ? force_id : superio_inb(SUPERIO_REG_DEVID);

/*
@@ -608,13 +617,14 @@ static int __init smsc47m1_find(struct smsc47m1_sio_data *sio_data)
static void smsc47m1_restore(const struct smsc47m1_sio_data *sio_data)
{
if ((sio_data->activate & 0x01) == 0) {
- superio_enter();
- superio_select();
-
- pr_info("Disabling device\n");
- superio_outb(SUPERIO_REG_ACT, sio_data->activate);
-
- superio_exit();
+ if (!superio_enter()) {
+ superio_select();
+ pr_info("Disabling device\n");
+ superio_outb(SUPERIO_REG_ACT, sio_data->activate);
+ superio_exit();
+ } else {
+ pr_warn("Failed to disable device\n");
+ }
}
}

--
2.20.1


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