If a transaction times out, the START_BUSY signal may have gotten stuck,
and subsequent transactaction attempts will fail as the bus is still
considered busy.
To work around this, check if the START_BUSY bit is still asserted, and
reset the controller in case it is.
This is also done by the alternative, non-upstream iproc-smbus driver
implementation [1].
Works around situations like:
bcm-iproc-2c 1803b000.i2c: transaction timed out
bcm-iproc-2c 1803b000.i2c: bus is busy
bcm-iproc-2c 1803b000.i2c: bus is busy
bcm-iproc-2c 1803b000.i2c: bus is busy
bcm-iproc-2c 1803b000.i2c: bus is busy
bcm-iproc-2c 1803b000.i2c: bus is busy
...
where the bus never recovers after a timeout.
[1] https://github.com/opencomputeproject/onie/blob/master/patches/kernel/3.2.69/driver-iproc-smbus.patch
Fixes: e6e5dd3566e0 ("i2c: iproc: Add Broadcom iProc I2C Driver")
Signed-off-by: Jonas Gorski <jonas.gorski@xxxxxxxx>
---
The iproc-smbus driver does some additional checks/mitigations, but
since my I2C understanding is only very rudimentary, I didn't add them,
also the reset was enough to fix the issue I was seeing.
I was a bit conflicted about the Fixes tag, but since it fixes/work
around misbehaviour seen I decided to add one.
The issue was happening only in production, and only once per boot (so
far), but with 100% probability within a few hours.
drivers/i2c/busses/i2c-bcm-iproc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
index 05c80680dff4..69f9c199fa3b 100644
--- a/drivers/i2c/busses/i2c-bcm-iproc.c
+++ b/drivers/i2c/busses/i2c-bcm-iproc.c
@@ -796,6 +796,15 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c,
if (!time_left && !iproc_i2c->xfer_is_done) {
dev_err(iproc_i2c->device, "transaction timed out\n");
+ /* check if START_BUSY did not clear */
+ if (!!(iproc_i2c_rd_reg(iproc_i2c, M_CMD_OFFSET) &
+ BIT(M_CMD_START_BUSY_SHIFT))) {
+ /* re-initialize i2c for recovery */
+ bcm_iproc_i2c_enable_disable(iproc_i2c, false);
+ bcm_iproc_i2c_init(iproc_i2c);
+ bcm_iproc_i2c_enable_disable(iproc_i2c, true);
+ }
+
/* flush both TX/RX FIFOs */
val = BIT(M_FIFO_RX_FLUSH_SHIFT) | BIT(M_FIFO_TX_FLUSH_SHIFT);
iproc_i2c_wr_reg(iproc_i2c, M_FIFO_CTRL_OFFSET, val);
--
2.42.0
--
BISDN GmbH
Körnerstraße 7-10
10785 Berlin
Germany
Phone:
+49-30-6108-1-6100
Managing Directors:
Dr.-Ing. Hagen Woesner, Andreas
Köpsel
Commercial register:
Amtsgericht Berlin-Charlottenburg HRB 141569
B
VAT ID No: DE283257294
