From: Jonas Gorski Date: Fri, 17 Jul 2026 08:55:07 +0000 (+0200) Subject: i2c: iproc: reset bus after timeout if START_BUSY is stuck X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=98f2e9e6d6f91a6abb43f166b244b428ba85fa2b;p=thirdparty%2Flinux.git i2c: iproc: reset bus after timeout if START_BUSY is stuck If a transaction times out, the START_BUSY signal can stay up, and subsequent transactaction attempts will fail as the bus is still considered busy. I can easily trigger this by attempting to read from an address with no device, e.g. when running i2cdetect. After the first read times out, all subsequent read attempts return busy. To get to a working state again, the controller needs to be reset to clear the START_BUSY signal. So check for START_BUSY still asserted on a timeout, and do reset in case it is, This is also done by the original 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 Cc: # v4.0+ Acked-by: Ray Jui Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260717085507.34209-1-jonas.gorski@bisdn.de --- diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c index b5629cffe99b..86ca4c2221c4 100644 --- a/drivers/i2c/busses/i2c-bcm-iproc.c +++ b/drivers/i2c/busses/i2c-bcm-iproc.c @@ -803,6 +803,17 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c, } if (!time_left && !iproc_i2c->xfer_is_done) { + /* + * The controller may fail to clear START_BUSY after a timeout, + * reset the controller to recover in that case. + */ + if (!!(iproc_i2c_rd_reg(iproc_i2c, M_CMD_OFFSET) & + BIT(M_CMD_START_BUSY_SHIFT))) { + 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);