Hi Stefan, On 2019-04-15 23:34, Stefan Lengfeld wrote: > Hi Wolfram, > > the following RFC patches are based on your branch > >> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/i2c/atomic_xfer > > I have used them to test your changes and my usecase on my available > hardware setup: an i.MX6 Solo (phyCORE-i.MX6). > > In general: Great stuff! And I vote for inclusion :-) > > Even so this series does not tackle all problems at once, it's a step > into the right direction to support reboot handlers using an external > PMIC via I2C. We have the same problem on our Colibri iMX7 board. Wolfram's patches made it already upstream, I applied your patches successfully on 5.4-rc1 and rebooting via I2C seems to work fine now! Hence we would like to see master_xfer_atomic support for the i.MX I2C driver too. Are you continuing working on this patch set? -- Stefan > > Some additional comments below and also in-line in your posted patches. > > >> a) we decided to respect the current locking scheme and to not give atomic >> transfers a priority. The code needed for that would have been either >> incomplete or very invasive. And we cannot guarantee successful transfers >> anyhow. See [1] for the discussion and other write-ups for design choices. > > Ack. I can just confirm that the mentioned locking issues are a real. I > could not reproduce them on my single core ARM SoC, but on a multi core > ARM system, e.g. the CPU frequency scaler is maybe holding the I2C > transfer mutex, while the system is going to restart. > > Just for reference: I 'solved' this by augmenting, read 'hacked', the > locking schema, so a single device driver can block the whole I2C bus > for itself and cause all other transfers to fail at once. See > > https://www.spinics.net/lists/linux-i2c/msg25399.html > > A real and good solution, as you said, is very invasive and must be > thought out carefully. > > > The appended patches are not meant for inclusion or review. They are > just for reference of my testing setup. > > Kind regards, > Stefan Lengfeld > > > Stefan Christ (1): > ARM: dts: phyboard-mira-dl: rely on PMIC for reboot and watchdog > > Stefan Lengfeld (2): > watchdog: da9062: avoid regmap in restart handler > i2c: imx: implement master_xfer_atomic callback > > .../boot/dts/imx6dl-phytec-mira-rdk-nand.dts | 8 ++ > drivers/i2c/busses/i2c-imx.c | 128 +++++++++++++----- > drivers/mfd/da9062-core.c | 1 + > drivers/watchdog/da9062_wdt.c | 17 ++- > include/linux/mfd/da9062/core.h | 1 + > 5 files changed, 116 insertions(+), 39 deletions(-)
