4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> commit 701dc207bf551d9fe6defa36e84a911e880398c3 upstream. 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@xxxxxxxx> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>: Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/i2c/busses/i2c-piix4.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) --- 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 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 mutex_unlock(&piix4_mutex_sb800); + /* Release the semaphore */ + outb_p(smbslvcnt | 0x20, SMBSLVCNT); + return retval; } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html