rtc: Provide flag for rtc devices that don't support UIE

commit 4a649903f91232d02284d53724b0a45728111767 upstream.

Richard Weinberger noticed that on some RTC hardware that
doesn't support UIE mode, due to coarse granular alarms
(like 1minute resolution), the current virtualized RTC
support doesn't properly error out when UIE is enabled.

Instead the current code queues an alarm for the next second,
but it won't fire until up to a miniute later.

This patch provides a generic way to flag this sort of hardware
and fixes the issue on the mpc5121 where Richard noticed the
problem.

Reported-by: Richard Weinberger <richard@nod.at>
Tested-by: Richard Weinberger <richard@nod.at>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index c1edbf8196524784155ae49ea91a919ad6c3d1a9..565742b9f0d01977cc7f18543f50ffe1d5a730da 100644 (file)
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -445,6 +445,11 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
        if (rtc->uie_rtctimer.enabled == enabled)
                goto out;
 
+       if (rtc->uie_unsupported) {
+               err = -EINVAL;
+               goto out;
+       }
+
        if (enabled) {
                struct rtc_time tm;
                ktime_t now, onesec;

diff --git a/drivers/rtc/rtc-mpc5121.c b/drivers/rtc/rtc-mpc5121.c
index da60915818b68cb526948e4e42111c89ded290ce..0fc2d221bc8be2566f6bd87671d9f93e7f386f71 100644 (file)
--- a/drivers/rtc/rtc-mpc5121.c
+++ b/drivers/rtc/rtc-mpc5121.c
@@ -360,6 +360,8 @@ static int __devinit mpc5121_rtc_probe(struct platform_device *op)
                                                &mpc5200_rtc_ops, THIS_MODULE);
        }
 
+       rtc->rtc->uie_unsupported = 1;
+
        if (IS_ERR(rtc->rtc)) {
                err = PTR_ERR(rtc->rtc);
                goto out_free_irq;

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 93f4d035076bc8f295fde5b0a6b5b89e4c5df9ff..fcabfb4873c8dd6e8466233de9d557be4bf2101e 100644 (file)
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -202,7 +202,8 @@ struct rtc_device
        struct hrtimer pie_timer; /* sub second exp, so needs hrtimer */
        int pie_enabled;
        struct work_struct irqwork;
-
+       /* Some hardware can't support UIE mode */
+       int uie_unsupported;
 
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
        struct work_struct uie_task;