Hello RCar Fans! Two issues people have seen with the i2c-rcar driver was: a) immediately restarted messages after NACK from client b) duplicated data bytes in messages Some people already worked on those and had a tough time because it was hard to reproduce these issues on non-customer setup. Luckily, I somewhen had a state where the first transfer after boot would always show the above issues on a plain Renesas Lager board. When measuring, I found a third issue thanks to my new tool 'i2ctransfer' (and thanks to projects like sigrok and OpenLogicSniffer, of course. Thank you very much!): c) after read message, no repeated start was sent, but stop + start. Due to some unlucky design choices in the IP core, it has some race windows which can cause problems if interrupts get delayed. Also, for every new message in one transfer, context switches between interrupt and process were needed. So I refactored the driver to setup new messages in interrupt context, too. This avoids the race for b) because we are now setting up the new message before we release the i2c bus clock (before we released the clock and set up the message in process context). c) is also fixed, this was not a race but a bug in the state handling. a) however is not fixed 100% :( We have the race window as small as possible now when utilizing interrupts, so it is an improvement and worked for my test cases well. There were experiments by me and Renesas engineers to use polling to prevent the issue but this caused other side effects, sadly. So, let's improve the situation now and let's see where we get. I did quite some lab testing here and also verified that slave support does not suffer from these changes. However, I'd really appreciate if people could give this real-world-testing which is always different. Please have a look, a test, etc... Thanks, Wolfram Wolfram Sang (9): i2c: rcar: rework hw init i2c: rcar: remove unused IOERROR state i2c: rcar: remove spinlock i2c: rcar: refactor setup of a msg i2c: rcar: init new messages in irq i2c: rcar: don't issue stop when HW does it automatically i2c: rcar: check master irqs before slave irqs i2c: rcar: revoke START request early i2c: rcar: clean up after refactoring drivers/i2c/busses/i2c-rcar.c | 193 ++++++++++++++++-------------------------- 1 file changed, 71 insertions(+), 122 deletions(-) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
