Messages in this thread | | | Date | Mon, 11 Sep 2023 16:09:54 +0200 | Subject | Re: [PATCH v3] i2c: designware: fix __i2c_dw_disable() in case master is holding SCL low | From | Yann Sionneau <> |
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Hi,
On 8/30/23 12:42, Jarkko Nikula wrote: > Hi > > On 8/22/23 12:02, Yann Sionneau wrote: >> The DesignWare IP can be synthesized with the >> IC_EMPTYFIFO_HOLD_MASTER_EN >> parameter. >> In this case, when the TX FIFO gets empty and the last command didn't >> have >> the STOP bit (IC_DATA_CMD[9]), the controller will hold SCL low until >> a new command is pushed into the TX FIFO or the transfer is aborted. >> >> When the controller is holding SCL low, it cannot be disabled. >> The transfer must first be aborted. >> Also, the bus recovery won't work because SCL is held low by the master. >> >> Check if the master is holding SCL low in __i2c_dw_disable() before >> trying >> to disable the controller. If SCL is held low, an abort is initiated. >> When the abort is done, then proceed with disabling the controller. >> >> This whole situation can happen for instance during SMBus read data >> block >> if the slave just responds with "byte count == 0". >> This puts the driver in an unrecoverable state, because the >> controller is >> holding SCL low and the current __i2c_dw_disable() procedure is not >> working. In this situation only a SoC reset can fix the i2c bus. >> >> Co-developed-by: Jonathan Borne <jborne@kalray.eu> >> Signed-off-by: Jonathan Borne <jborne@kalray.eu> >> Signed-off-by: Yann Sionneau <ysionneau@kalray.eu> >> --- >> V2 -> V3: >> * do not rename timeout variable for disabling loop >> in order to ease backports >> * replace abort loop with regmap_read_poll_timeout() >> * remove extra empty line. >> >> V1 -> V2: >> * use reverse christmas tree order for variable declarations >> * use unsigned int type instead of u32 for regmap_read >> * give its own loop to the abort procedure with its own timeout >> * print an error message if the abort never finishes during the timeout >> * rename the timeout variable for the controller disabling loop >> * with the usleep_range(10, 20) it takes only 1 loop iteration. >> Without it takes 75 iterations and with udelay(1) it takes 16 >> loop iterations. >> >> drivers/i2c/busses/i2c-designware-common.c | 17 +++++++++++++++++ >> drivers/i2c/busses/i2c-designware-core.h | 3 +++ >> 2 files changed, 20 insertions(+) >> > This doesn't apply against current code. Looks like your base is older > than v6.2? I.e. before commit 966b7d3c738a ("i2c: designware: Align > defines in i2c-designware-core.h").
Oops, I've rebased it on v6.6-rc1 and re-sent it as V4.
Thanks.
Regards,
--
Yann
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