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| author | Ricardo Ribalda <ricardo.ribalda@gmail.com> | 2017-01-11 10:11:44 +0100 |
|---|---|---|
| committer | Wolfram Sang <wsa@the-dreams.de> | 2017-01-12 20:52:12 +0100 |
| commit | 701dc207bf551d9fe6defa36e84a911e880398c3 (patch) | |
| tree | 7ec8b3ac8cd6431cbf19bc88b1ec273ed87a10f2 /drivers/i2c | |
| parent | i2c: fix spelling mistake: "insufficent" -> "insufficient" (diff) | |
| download | linux-701dc207bf551d9fe6defa36e84a911e880398c3.tar.xz linux-701dc207bf551d9fe6defa36e84a911e880398c3.zip | |
i2c: piix4: Avoid race conditions with IMC
On AMD's SB800 and upwards, the SMBus is shared with the Integrated
Micro Controller (IMC).
The platform provides a hardware semaphore to avoid race conditions
among them. (Check page 288 of the SB800-Series Southbridges Register
Reference Guide http://support.amd.com/TechDocs/45482.pdf)
Without this patch, many access to the SMBus end with an invalid
transaction or even with the bus stalled.
Reported-by: Alexandre Desnoyers <alex@qtec.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>:
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/busses/i2c-piix4.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c index c2268cdf38e8..e34d82e79b98 100644 --- a/drivers/i2c/busses/i2c-piix4.c +++ b/drivers/i2c/busses/i2c-piix4.c @@ -585,10 +585,29 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr, u8 command, int size, union i2c_smbus_data *data) { struct i2c_piix4_adapdata *adapdata = i2c_get_adapdata(adap); + unsigned short piix4_smba = adapdata->smba; + int retries = MAX_TIMEOUT; + int smbslvcnt; u8 smba_en_lo; u8 port; int retval; + /* Request the SMBUS semaphore, avoid conflicts with the IMC */ + smbslvcnt = inb_p(SMBSLVCNT); + do { + outb_p(smbslvcnt | 0x10, SMBSLVCNT); + + /* Check the semaphore status */ + smbslvcnt = inb_p(SMBSLVCNT); + if (smbslvcnt & 0x10) + break; + + usleep_range(1000, 2000); + } while (--retries); + /* SMBus is still owned by the IMC, we give up */ + if (!retries) + return -EBUSY; + mutex_lock(&piix4_mutex_sb800); outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX); @@ -606,6 +625,9 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr, mutex_unlock(&piix4_mutex_sb800); + /* Release the semaphore */ + outb_p(smbslvcnt | 0x20, SMBSLVCNT); + return retval; } |