[PATCH] RTC: TWL: ensure all interrupts are disabled during probe

[Shubhrajyoti Datta]

Hi Kevin,

On Fri, Sep 14, 2012 at 2:15 AM, Kevin Hilman
<khilman at deeprootsystems.com> wrote:
> From: Kevin Hilman <khilman at ti.com>
>
> 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 at ti.com>
> Cc: Steve Sakoman <steve at sakoman.com>
> Signed-off-by: Kevin Hilman <khilman at ti.com>
> ---
> 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
>
>
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