[PATCH RESEND 0/2] rtc: initial patches to fix borkage of rtc-s35390a

[PATCH RESEND 0/2] rtc: initial patches to fix borkage of rtc-s35390a

[Uwe Kleine-König]

Hello,

[I'm resending because only a single patch made it to the rtc list, don't know
why.]

here are two patches that improve the rtc core's robustness regarding
stuff the rtc-s35390a does. That is in .read_alarm it only assigns
alm->time.tm_wday, alm->time.tm_hour and alm->time.tm_min which as of
now makes the kernel report things like:

	[    2.257418] rtc rtc0: invalid alarm value: 1900-1-29 1193031:57:16

.

The open issues (I'm aware of) but which are orthogonal to the patches
here are:

 - The core doesn't handle a driver setting alm->time.tm_wday but not
   alm->time.tm_mday.
 - The chip has status bits that signal if an irq is pending, but these
   are cleared at read and the first read during driver probe doesn't
   check for these bits set. (There are more such read-to-clear bits,
   e.g. when the battery backing was lost ...)
   The result is that the irq isn't acked (by unsetting INT2AE) which
   prevents some devices (e.g. QNAP TS-41x) to shutdown.
   (https://bugs.debian.org/794266)

So with the two patches in this series the QNAP TS-41x still fails to
shutdown, but it is handled a bit better. 

I'd consider this merge window material.

Uwe Kleine-König (2):
  rtc: initialize output parameter for read alarm to "uninitialized"
  rtc: make rtc_time64_to_tm save to use for dates before 1970

 drivers/rtc/interface.c | 12 +++++++++++-
 drivers/rtc/rtc-lib.c   | 13 +++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

-- 
2.8.1

[rtc-linux] [PATCH RESEND 1/2] rtc: initialize output parameter for read alarm to "uninitialized"

[Uwe Kleine-König]

rtc drivers are supposed to set values they don't support to -1. To
simplify this for drivers and also make it harder for them to get it
wrong initialize the values to -1.

Signed-off-by: Uwe Kleine-K=C3=B6nig <uwe@kleine-koenig.org>
---
 drivers/rtc/interface.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 9ef5f6f89f98..99475908e556 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -104,7 +104,17 @@ static int rtc_read_alarm_internal(struct rtc_device *=
rtc, struct rtc_wkalrm *al
 	else if (!rtc->ops->read_alarm)
 		err =3D -EINVAL;
 	else {
-		memset(alarm, 0, sizeof(struct rtc_wkalrm));
+		alarm->enabled =3D 0;
+		alarm->pending =3D 0;
+		alarm->time.tm_sec =3D -1;
+		alarm->time.tm_min =3D -1;
+		alarm->time.tm_hour =3D -1;
+		alarm->time.tm_mday =3D -1;
+		alarm->time.tm_mon =3D -1;
+		alarm->time.tm_year =3D -1;
+		alarm->time.tm_wday =3D -1;
+		alarm->time.tm_yday =3D -1;
+		alarm->time.tm_isdst =3D -1;
 		err =3D rtc->ops->read_alarm(rtc->dev.parent, alarm);
 	}
=20
--=20
2.8.1

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[rtc-linux] [PATCH RESEND 2/2] rtc: make rtc_time64_to_tm save to use for dates before 1970

[Uwe Kleine-König]

When the time parameter to rtc_time64_to_tm is negative and so
represents a date before 1970 several outputs were calculated wrongly.
A comment in the code signaled that the code doesn't handle negative
times but that didn't stop __rtc_read_alarm to still pass negative
values.

For example with time=3D-2208565980 (1900-01-05 21:27 UTC) the days variabl=
e
was assigned a negative value (-25562) which was then used to calculate

	secs =3D time - (unsigned int) days * 86400;

resulting in an overflow in both the multiplication and the subtraction
yielding secs =3D 4294958116 which is then used to calculate
tm_hour =3D 1193043; tm_min =3D 55; tm_sec =3D 16.

With the changes in this patch the time stamp from the example above is
converted correctly.

Signed-off-by: Uwe Kleine-K=C3=B6nig <uwe@kleine-koenig.org>
---
 drivers/rtc/rtc-lib.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
index e6bfb9c42a10..0140ce7088ac 100644
--- a/drivers/rtc/rtc-lib.c
+++ b/drivers/rtc/rtc-lib.c
@@ -53,15 +53,20 @@ EXPORT_SYMBOL(rtc_year_days);
 void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
 {
 	unsigned int month, year;
-	unsigned long secs;
+	s32 secs
 	int days;
=20
-	/* time must be positive */
-	days =3D div_s64(time, 86400);
-	secs =3D time - (unsigned int) days * 86400;
+	days =3D div_s64_rem(time, 86400, &secs);
+
+	if (secs < 0) {
+		secs +=3D 86400;
+		days -=3D 1;
+	}
=20
 	/* day of the week, 1970-01-01 was a Thursday */
 	tm->tm_wday =3D (days + 4) % 7;
+	if (tm->tm_wday < 0)
+		tm->tm_wday +=3D 7;
=20
 	year =3D 1970 + days / 365;
 	days -=3D (year - 1970) * 365
--=20
2.8.1

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[rtc-linux] Re: [PATCH RESEND 1/2] rtc: initialize output parameter for read alarm to "uninitialized"

[Alexandre Belloni]

On 11/05/2016 at 09:11:23 +0200, Uwe Kleine-K=C3=B6nig wrote :
> rtc drivers are supposed to set values they don't support to -1. To
> simplify this for drivers and also make it harder for them to get it
> wrong initialize the values to -1.
>=20
> Signed-off-by: Uwe Kleine-K=C3=B6nig <uwe@kleine-koenig.org>
> ---
>  drivers/rtc/interface.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>=20
Applied, thanks.

--=20
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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