From 8dcebaa9a0ae8a0487f4342f3d56d2cb1c980860 Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Mon, 17 Sep 2012 14:09:17 -0700 Subject: [PATCH] drivers/rtc/rtc-twl.c: ensure all interrupts are disabled during probe 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 Cc: Felipe Balbi Tested-by: Steve Sakoman Cc: Alessandro Zummo Tested-by: Shubhrajyoti Datta Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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"); + /* init cached IRQ enable bits */ ret = twl_rtc_read_u8(&rtc_irq_bits, REG_RTC_INTERRUPTS_REG); if (ret < 0) -- 2.7.4