On Tue, Jan 09, 2018 at 02:58:53PM +0100, Wolfram Sang wrote: > From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> > > 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. The first five patches may be interesting for anyone, so input > is greatly appreciated. Also, testing the new features with GPIO based recovery > would be awesome to have. Thanks to Phil for testing already! > > 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. > > Changes since V1: > > * add more identifiers in patch 2 > * don't use GPIOF_* flags but hardocded '0' > * added Phil's Tested-by > > > > 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 | 26 ++++++++++++--------- > 3 files changed, 91 insertions(+), 14 deletions(-) Applied to for-next, thanks!
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