Hi Wolfram, Thank you for the patches. For the whole series, Tested-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> On Thursday 19 November 2015 16:56:40 Wolfram Sang wrote: > Hello RCar Fans! > > So, here is V3 of this series. After a debugging session with Laurent, we > finally fixed his issue for good. It was not board dependent as we thought, > but toolchain dependent! Hidden by a macro, the driver used a compound > assignemt with a function call as the rvalue. After patch 6, this function > also changed the flags which were to be changed by the compound assignment. > Basically (after macro): > > priv->flags |= i_change_priv_flags(priv); > > Which is undefined behaviour, I guess. However, after my refactoring, the > called functions always returned 0, so we can simply do: > > i_change_priv_flags(priv); > > Nasty one, but finally issue gone, for all toolchains and optimization > settings. Furthermore, patch 11 has been added because HW engineers wanted > it. > > The branch can be found here: > > git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git > renesas/rcar-i2c-rework-v3 > > Please test, test, test :) > > Wolfram > > > Changes since V2: > * patch 6/11 was cleaned up to not use the compund assignment > * patch 11/11 introduced as requested by HW engineers > > Changes since V1: > * new patch 1/10 to ensure clock is always on > * rebased patch 2/10 to the new patch > * some patch descriptions slightly reworded > > > Here is the description of the V1 series for those who missed it: > > 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 (11): > i2c: rcar: make sure clocks are on when doing clock calculation > 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 > i2c: rcar: handle difference in setting up non-first message > > drivers/i2c/busses/i2c-rcar.c | 249 +++++++++++++++++---------------------- > 1 file changed, 106 insertions(+), 143 deletions(-) -- Regards, Laurent Pinchart -- 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
