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authorRicardo Ribalda <ricardo.ribalda@gmail.com>2017-01-11 10:11:44 +0100
committerWolfram Sang <wsa@the-dreams.de>2017-01-12 20:52:12 +0100
commit701dc207bf551d9fe6defa36e84a911e880398c3 (patch)
tree7ec8b3ac8cd6431cbf19bc88b1ec273ed87a10f2
parent2659161dd40dbb599a19f320164373093df44a89 (diff)
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>
-rw-r--r--drivers/i2c/busses/i2c-piix4.c22
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;
}