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    Subject[ 097/262] drivers/rtc/rtc-twl.c: ensure all interrupts are disabled during probe
    Date
    From: Greg KH <gregkh@linuxfoundation.org>

    3.5-stable review patch. If anyone has any objections, please let me know.

    ------------------

    From: Kevin Hilman <khilman@ti.com>

    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 <khilman@ti.com>
    Cc: Felipe Balbi <balbi@ti.com>
    Tested-by: Steve Sakoman <steve@sakoman.com>
    Cc: Alessandro Zummo <a.zummo@towertech.it>
    Tested-by: Shubhrajyoti Datta <omaplinuxkernel@gmail.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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)



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