When implementing bus recovery for the i2c-rcar driver, two problems were encountered: 1) When reading the SDA bit, not the SDA status was returned but the internal state of the "bus_is_busy" logic. 2) This logic needs a STOP to consider the bus free again. SCL/SDA high is not enough, and there is no other way known to reset the internal logic otherwise. The obvious solution to just send STOP after recovery makes sense for the generic case, too, IMO. If we made a device release SDA again, and are about start a new transfer using START, then we should terminate the previous state properly with STOP. This may help with some devices and shouldn't create any drawback AFAICS. For this, we need to introduce a 'set_sda' callback to the recovery infrastructure. Because of this and some other minor recovery core changes, I CCed a few people working on I2C bus recovery recently. The first five patches may be interesting for you, so your input is greatly appreciated. Also, testing the new features with GPIO based recovery would be awesome to have. This was tested on a Renesas Lager board (r8a7790/R-Car H2). My test procedure is documented here: https://elinux.org/Tests:I2C-bus-recovery A branch is available here: git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/rcar-i2c-recovery Please let me know what you think. Kind regards, Wolfram Wolfram Sang (6): i2c: make kerneldoc about bus recovery more precise i2c: add identifier in declarations for i2c_bus_recovery i2c: add 'set_sda' to bus_recovery_info i2c: ensure SDA is released in recovery if SDA is controllable i2c: send STOP after successful bus recovery i2c: rcar: implement bus recovery drivers/i2c/busses/i2c-rcar.c | 54 +++++++++++++++++++++++++++++++++++++++++-- drivers/i2c/i2c-core-base.c | 25 +++++++++++++++++++- include/linux/i2c.h | 20 +++++++++------- 3 files changed, 88 insertions(+), 11 deletions(-) -- 2.11.0
