On Wed, Jan 11, 2017 at 11:11 AM, Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> wrote: > 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. > After addressing below comment FWIW: Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>: > Credit-to: Alexandre Desnoyers <alex@xxxxxxxx> It would be nice to put in plain test what you tell in the discussion here instead of non-standard (see submitting-patches.rst) tag. > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> > --- > > v2: Suggestions by Andy Shevchenko <andy.shevchenko@xxxxxxxxx>: > -Rename timeout to retries > -Use do {} while(--retries) pattern > -Group new variables > > > drivers/i2c/busses/i2c-piix4.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c > index f0563f7ce01b..81d06be0a72d 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; > } > > -- > 2.11.0 > -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
