[PATCH 4.9 021/108] i2c: piix4: Request the SMBUS semaphore inside the mutex

Greg Kroah-Hartman
2017-06-15T17:57:42Z

From: Ricardo Ribalda <ricardo.ribalda@gmail.com>

[ Upstream commit bbb27fc33d44e7b8d96369810654df4ee1837566 ]

SMBSLVCNT must be protected with the piix4_mutex_sb800 in order to avoid
multiple buses accessing to the semaphore at the same time.

Fixes: 701dc207bf55 ("i2c: piix4: Avoid race conditions with IMC")
Reported-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/i2c/busses/i2c-piix4.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -592,6 +592,8 @@ static s32 piix4_access_sb800(struct i2c
u8 port;
int retval;

+ mutex_lock(&piix4_mutex_sb800);
+
/* Request the SMBUS semaphore, avoid conflicts with the IMC */
smbslvcnt = inb_p(SMBSLVCNT);
do {
@@ -605,10 +607,10 @@ static s32 piix4_access_sb800(struct i2c
usleep_range(1000, 2000);
} while (--retries);
/* SMBus is still owned by the IMC, we give up */
- if (!retries)
+ if (!retries) {
+ mutex_unlock(&piix4_mutex_sb800);
return -EBUSY;
-
- mutex_lock(&piix4_mutex_sb800);
+ }

outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
@@ -623,11 +625,11 @@ static s32 piix4_access_sb800(struct i2c

outb_p(smba_en_lo, SB800_PIIX4_SMB_IDX + 1);

- mutex_unlock(&piix4_mutex_sb800);
-
/* Release the semaphore */
outb_p(smbslvcnt | 0x20, SMBSLVCNT);

+ mutex_unlock(&piix4_mutex_sb800);
+
return retval;
}