Shubhrajyoti Datta <omaplinuxkernel@xxxxxxxxx> writes: > Hi Kevin, > > On Fri, Sep 14, 2012 at 2:15 AM, Kevin Hilman > <khilman@xxxxxxxxxxxxxxxxxxx> wrote: >> From: Kevin Hilman <khilman@xxxxxx> >> >> On some platforms, bootloaders are known to do some interesting RTC >> programming. Without going into the obscurities as to why this may be >> the case, suffice it to say the the driver should not make any >> assumptions about the state of the RTC when the driver loads. In >> particular, the driver probe should be sure that all interrupts are >> disabled until otherwise programmed. >> >> This was discovered when finding bursty I2C traffic every second on >> Overo platforms. This I2C overhead was keeping the SoC from hitting >> deep power states. The cause was found to be the RTC firing every >> second on the I2C-connected TWL PMIC. >> >> Special thanks to Felipe Balbi for suggesting to look for a rogue >> driver as the source of the I2C traffic rather than the I2C driver >> itself. >> >> Special thanks to Steve Sakoman for helping track down the source of >> the continuous RTC interrups on the Overo boards. >> > > Tested that the continuous interrupt issue after doing a i2c mm on omap4sdp. > This patch solves the issue. > thanks, > >> Cc: Felipe Balbi <balbi@xxxxxx> >> Cc: Steve Sakoman <steve@xxxxxxxxxxx> >> Signed-off-by: Kevin Hilman <khilman@xxxxxx> >> --- >> Patch applies to v3.6-rc5 >> >> drivers/rtc/rtc-twl.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/drivers/rtc/rtc-twl.c b/drivers/rtc/rtc-twl.c >> index c5d06fe..9277d94 100644 >> --- a/drivers/rtc/rtc-twl.c >> +++ b/drivers/rtc/rtc-twl.c >> @@ -495,6 +495,11 @@ static int __devinit twl_rtc_probe(struct platform_device *pdev) >> if (ret < 0) >> goto out1; >> >> + /* ensure interrupts are disabled, bootloaders can be strange */ >> + ret = twl_rtc_write_u8(0, REG_RTC_INTERRUPTS_REG); >> + if (ret < 0) >> + dev_warn(&pdev->dev, "unable to disable interrupt\n"); >> + > Now that it is always 0 can the below read be removed as it is redundant now. Possibly, but I don't know this HW well enough to know if there are any persistent bits in that register on any of the various derivations of this PMIC. Since this read-back value is used throughout the driver, I decided not to mess with it when doing this targetted fix. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
