sam460ex, rtc-m41t80 incorrect behaviour with kernel >=linux-2.6.38

Quoted 8 lines · On Sun, 2011-12-04 at 03:29 +0100, [email protected] wrote:

Acube Sam460ex is a 460ex SoC (PowerPC) based board with m41t81 like RTC. The wrong beahviour it seems to be caused this commit:

Thu, 3 Feb 2011 21:02:35 +0000 (13:02 -0800)
commit 16380c153a69c3784d2afaddfe0a22f353046cf6
RTC: Convert rtc drivers to use the alarm_irq_enable method
http://git.kernel.org/?p=linux/kernel/git/next/linux-next.git;a=commit;
h=16380c153a69c3784d2afaddfe0a22f353046cf6

Yea. This was reported earlier, but it seems none of the proposed solutions have been implemented.

The cause is that the m41t80 driver's alarm functionality is somehow broken. The alarm mode is actually now used for UIE, so where before 2.6.38, UIE mode returned -EINVAL, it will now succeed, setting the alarm to fire a second away.

However, since the alarm code is broken, no alarm arrives and you get the timeout you see.

Could you test the following patch to see if it resolves the issue for you? If it does, I'll queue it for inclusion.

thanks
-john

[PATCH] rtc: m41t80: Workaround broken alarm functionality

The m41t80 driver doesn't seem to have a functional alarm.

This causes failures when the generic core sees alarm functions, but then cannot use them properly for things like UIE mode.

Disabling the alarm functions allows proper error reporting, and possible fallback to emulated modes. Once someone fixes the alarm functions, this can be restored.

Signed-off-by John Stultz <[email protected]>

---
 drivers/rtc/rtc-m41t80.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

drivers/rtc/rtc-m41t80.c +9 -0

index eda128f..64aedd8 100644
@@ -357,10 +357,19 @@ static int m41t80_rtc_read_alarm(struct device
 *dev, struct rtc_wkalrm *t) static struct rtc_class_ops
 m41t80_rtc_ops = { .read_time = m41t80_rtc_read_time,
 	.set_time = m41t80_rtc_set_time,
+	/*
+	 * XXX - m41t80 alarm functionality is reported broken.
+	 * until it is fixed, don't register alarm functions.
+	 *
 	.read_alarm = m41t80_rtc_read_alarm,
 	.set_alarm = m41t80_rtc_set_alarm,
+	*/
 	.proc = m41t80_rtc_proc,
+	/*
+	 * See above comment on broken alarm
+	 *
 	.alarm_irq_enable = m41t80_rtc_alarm_irq_enable,
+	*/
 };
 
 #if defined(CONFIG_RTC_INTF_SYSFS) || defined

#(CONFIG_RTC_INTF_SYSFS_MODULE)

Signature · 1 line

1.7.3.2.146.gca209