If the RTC HW returns an invalid time, the rtc_year_days()
call would crash. This patch adds error logging in this
situation, and removes the tm_yday and tm_wday calculations.
These fields should not be relied upon by userspace
according to man rtc, and thus we don't need to calculate
them.

Signed-off-by: Nick Crews <ncr...@chromium.org>
---
 drivers/rtc/rtc-wilco-ec.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
index 8ad4c4e6d557..53da355d996a 100644
--- a/drivers/rtc/rtc-wilco-ec.c
+++ b/drivers/rtc/rtc-wilco-ec.c
@@ -110,10 +110,15 @@ static int wilco_ec_rtc_read(struct device *dev, struct 
rtc_time *tm)
        tm->tm_mday     = rtc.day;
        tm->tm_mon      = rtc.month - 1;
        tm->tm_year     = rtc.year + (rtc.century * 100) - 1900;
-       tm->tm_yday     = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
-
-       /* Don't compute day of week, we don't need it. */
-       tm->tm_wday = -1;
+       /* Ignore other tm fields, man rtc says userspace shouldn't use them. */
+
+       if (rtc_valid_tm(tm)) {
+               dev_err(dev,
+                        "Time from RTC is invalid: second=%u, minute=%u, 
hour=%u, day=%u, month=%u, year=%u, century=%u",
+                        rtc.second, rtc.minute, rtc.hour, rtc.day, rtc.month,
+                        rtc.year, rtc.century);
+               return -EIO;
+       }
 
        return 0;
 }
-- 
2.21.0

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