On Fri, Mar 1, 2019 at 8:03 PM Tony Lindgren <tony@xxxxxxxxxxx> wrote: > From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> > > Tony notes that the GPIO module does not idle when level interrupts are > in use, as the wakeup appears to get stuck. > > After extensive investigation, it appears that the wakeup will only be > cleared if the interrupt status register is cleared while the interrupt > is enabled. However, we are currently clearing it with the interrupt > disabled for level-based interrupts. > > It is acknowledged that this observed behaviour conflicts with a > statement in the TRM: > > CAUTION > After servicing the interrupt, the status bit in the interrupt status > register (GPIOi.GPIO_IRQSTATUS_0 or GPIOi.GPIO_IRQSTATUS_1) must be > reset and the interrupt line released (by setting the corresponding > bit of the interrupt status register to 1) before enabling an > interrupt for the GPIO channel in the interrupt-enable register > (GPIOi.GPIO_IRQSTATUS_SET_0 or GPIOi.GPIO_IRQSTATUS_SET_1) to prevent > the occurrence of unexpected interrupts when enabling an interrupt > for the GPIO channel. > > However, this does not appear to be a practical problem. > > Further, as reported by Grygorii Strashko <grygorii.strashko@xxxxxx>, > the TI Android kernel tree has an earlier similar patch as "GPIO: OMAP: > Fix the sequence to clear the IRQ status" saying: > > if the status is cleared after disabling the IRQ then sWAKEUP will not > be cleared and gates the module transition > > When we unmask the level interrupt after the interrupt has been handled, > enable the interrupt and only then clear the interrupt. If the interrupt > is still pending, the hardware will re-assert the interrupt status. > > Should the caution note in the TRM prove to be a problem, we could > use a clear-enable-clear sequence instead. > > Cc: Aaro Koskinen <aaro.koskinen@xxxxxx> > Cc: Grygorii Strashko <grygorii.strashko@xxxxxx> > Cc: Keerthy <j-keerthy@xxxxxx> > Cc: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> > [tony@xxxxxxxxxxx: updated comments based on an earlier TI patch] > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> Patch applied! Really nice debugging here. Yours, Linus Walleij
