On Thu, Sep 03, 2015 at 10:20:04PM +0200, Wolfram Sang wrote: > 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 > Applied to for-next, thanks!
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