3.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Kevin Hilman <[email protected]> commit 8dcebaa9a0ae8a0487f4342f3d56d2cb1c980860 upstream. 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. Signed-off-by: Kevin Hilman <[email protected]> Cc: Felipe Balbi <[email protected]> Tested-by: Steve Sakoman <[email protected]> Cc: Alessandro Zummo <[email protected]> Tested-by: Shubhrajyoti Datta <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/rtc/rtc-twl.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/rtc/rtc-twl.c +++ b/drivers/rtc/rtc-twl.c @@ -495,6 +495,11 @@ static int __devinit twl_rtc_probe(struc 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"); + /* init cached IRQ enable bits */ ret = twl_rtc_read_u8(&rtc_irq_bits, REG_RTC_INTERRUPTS_REG); if (ret < 0) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
