On 14.05.2018 15:18, Wolfram Sang wrote: > On Mon, May 14, 2018 at 01:59:33PM +0200, Thierry Reding wrote: >> On Mon, May 14, 2018 at 12:13:47AM +0300, Dmitry Osipenko wrote: >>> Nothing prevents I2C clients to access I2C while Tegra's driver is being >>> suspended, this results in -EBUSY error returned to the clients and that >>> may have unfortunate consequences. In particular this causes problems >>> for the TPS6586x MFD driver which emits hundreds of "failed to read >>> interrupt status" error messages on resume from suspend. This happens if >>> TPS6586X is used to wake system from suspend by the expired RTC alarm >>> timer because TPS6586X is an I2C device driver and its IRQ handler reads >>> the status register while Tegra's I2C driver is suspended, i.e. just after >>> kernel enabled IRQ's during of resume-from-suspend process. >>> >>> Note that the removed tegra_i2c_resume() invoked tegra_i2c_init() which >>> performs HW reset. That seems was also not entirely correct because moving >>> tegra_i2c_resume to an earlier stage of resume-from-suspend process causes >>> I2C transfer to fail in the case of TPS6586X. It is fine to remove the >>> HW-reinitialization for now because it should be only needed in a case of >>> using lowest power-mode during suspend, which upstream kernel doesn't >>> support. >>> >>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >>> Cc: <stable@xxxxxxxxxxxxxxx> >>> --- >>> drivers/i2c/busses/i2c-tegra.c | 33 --------------------------------- >>> 1 file changed, 33 deletions(-) >> >> Shardar, Laxman, any thoughts on this? The is_suspended thing looks to >> me like a workaround of some sort that may not be needed if clients have >> proper suspend/resume implementations. Even without suspend/resume >> support in client drivers, the driver core should resume devices in the >> right order (I2C adapter before any of the clients), so I don't see any >> cases where the is_suspended logic would be useful. > > Thanks for this patch! > > This is closely related to a discussion we started recently: > > "I2C PM overhaul needed?" https://lkml.org/lkml/2018/5/4/329 > > And part of the outcome is that the I2C core should print a WARN if an > I2C client tries to use I2C at suspend_noirq state or later. This is to > remove logic like in this patch from all I2C host drivers and to make it > more explicit that those I2C client drivers need their PM fixed. > Thank you very much for pointing at the discussion. Indeed it should be nicer if I2C core handled the buggy client drivers and the rest of related suspend/resume issues instead of having each I2C BUS driver to do it on its own. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
