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. > /* init cached IRQ enable bits */ > ret = twl_rtc_read_u8(&rtc_irq_bits, REG_RTC_INTERRUPTS_REG); > if (ret < 0) > -- > 1.7.9.2 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- 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
