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rtc: msc313: Fix unintentional sign extension issues with left shift of a u16 

Shifting the u16 value returned by readw by 16 bits to the left
will be promoted to a 32 bit signed int and then sign-extended
to an unsigned long. If the top bit of the readw is set then
the shifted value will be sign extended and the top 32 bits of
the result will be set.

Fixes: be7d9c9161 ("rtc: Add support for the MSTAR MSC313 RTC")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Romain Perier <romain.perier@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210928134654.991923-1-colin.king@canonical.com
This commit is contained in:
Colin Ian King 2021-09-28 14:46:54 +01:00 committed by Alexandre Belloni
parent 3109151c47
commit f3606687b4
1 changed files with 2 additions and 2 deletions
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4
drivers/rtc/rtc-msc313.c
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@ -53,7 +53,7 @@ static int msc313_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
unsigned long seconds;
seconds = readw(priv->rtc_base + REG_RTC_MATCH_VAL_L)
| (readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
| ((unsigned long)readw(priv->rtc_base + REG_RTC_MATCH_VAL_H) << 16);
rtc_time64_to_tm(seconds, &alarm->time);
@ -122,7 +122,7 @@ static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm)
udelay(1);
seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L)
| (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
| ((unsigned long)readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
rtc_time64_to_tm(seconds, tm);