path: root/drivers/rtc/rtc-twl.c
diff options
authorKevin Hilman <khilman@ti.com>2012-09-17 14:09:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-09-17 15:00:38 -0700
commit8dcebaa9a0ae8a0487f4342f3d56d2cb1c980860 (patch)
tree66b09ae6518184136d0df8eb77dd98180d0a2769 /drivers/rtc/rtc-twl.c
parent9a858dc7cebce01a7bb616bebb85087fa2b40871 (diff)
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 <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> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/rtc/rtc-twl.c')
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-twl.c b/drivers/rtc/rtc-twl.c
index c5d06fe83bb..9277d945bf4 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)