/proc/acpi/alarm: handle day-of-month wraparound on readback

Fix month wrap issue with readback from /proc/acpi/alarm
This bug has been around *forever*.

  $ echo '2008-12-01 10:36:20' > /proc/acpi/alarm
  $ cat /proc/acpi/alarm
  2008-11-01 10:36:20

Note how the readback above shows the month incorrectly
when the alarm is set in the *next* calendar month.
But with this patch applied, it shows the correct month (12).

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 32 insertions, 21 deletions

diff --git a/drivers/acpi/sleep/proc.c b/drivers/acpi/sleep/proc.c
index 4dbc2271acf5..232d4b64140b 100644
--- a/drivers/acpi/sleep/proc.c
+++ b/drivers/acpi/sleep/proc.c
@@ -84,12 +84,15 @@ acpi_system_write_sleep(struct file *file,
 #define HAVE_ACPI_LEGACY_ALARM
 #endif
 
+static u32 cmos_bcd_read(int offset, int rtc_control);
+
 #ifdef  HAVE_ACPI_LEGACY_ALARM
 
 static int acpi_system_alarm_seq_show(struct seq_file *seq, void *offset)
 {
         u32 sec, min, hr;
         u32 day, mo, yr, cent = 0;
+        u32 today = 0;
         unsigned char rtc_control = 0;
         unsigned long flags;
 
@@ -97,38 +100,32 @@ static int acpi_system_alarm_seq_show(struct seq_file *seq, void *offset)
 
         spin_lock_irqsave(&rtc_lock, flags);
 
-        sec = CMOS_READ(RTC_SECONDS_ALARM);
-        min = CMOS_READ(RTC_MINUTES_ALARM);
-        hr = CMOS_READ(RTC_HOURS_ALARM);
         rtc_control = CMOS_READ(RTC_CONTROL);
+        sec = cmos_bcd_read(RTC_SECONDS_ALARM, rtc_control);
+        min = cmos_bcd_read(RTC_MINUTES_ALARM, rtc_control);
+        hr = cmos_bcd_read(RTC_HOURS_ALARM, rtc_control);
 
         /* If we ever get an FACP with proper values... */
-        if (acpi_gbl_FADT.day_alarm)
+        if (acpi_gbl_FADT.day_alarm) {
                 /* ACPI spec: only low 6 its should be cared */
                 day = CMOS_READ(acpi_gbl_FADT.day_alarm) & 0x3F;
-        else
-                day = CMOS_READ(RTC_DAY_OF_MONTH);
+                if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+                        day = bcd2bin(day);
+        } else
+                day = cmos_bcd_read(RTC_DAY_OF_MONTH, rtc_control);
         if (acpi_gbl_FADT.month_alarm)
-                mo = CMOS_READ(acpi_gbl_FADT.month_alarm);
-        else
-                mo = CMOS_READ(RTC_MONTH);
+                mo = cmos_bcd_read(acpi_gbl_FADT.month_alarm, rtc_control);
+        else {
+                mo = cmos_bcd_read(RTC_MONTH, rtc_control);
+                today = cmos_bcd_read(RTC_DAY_OF_MONTH, rtc_control);
+        }
         if (acpi_gbl_FADT.century)
-                cent = CMOS_READ(acpi_gbl_FADT.century);
+                cent = cmos_bcd_read(acpi_gbl_FADT.century, rtc_control);
 
-        yr = CMOS_READ(RTC_YEAR);
+        yr = cmos_bcd_read(RTC_YEAR, rtc_control);
 
         spin_unlock_irqrestore(&rtc_lock, flags);
 
-        if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
-                sec = bcd2bin(sec);
-                min = bcd2bin(min);
-                hr = bcd2bin(hr);
-                day = bcd2bin(day);
-                mo = bcd2bin(mo);
-                yr = bcd2bin(yr);
-                cent = bcd2bin(cent);
-        }
-
         /* we're trusting the FADT (see above) */
         if (!acpi_gbl_FADT.century)
                 /* If we're not trusting the FADT, we should at least make it
@@ -153,6 +150,20 @@ static int acpi_system_alarm_seq_show(struct seq_file *seq, void *offset)
         else
                 yr += cent * 100;
 
+        /*
+         * Show correct dates for alarms up to a month into the future.
+         * This solves issues for nearly all situations with the common
+         * 30-day alarm clocks in PC hardware.
+         */
+        if (day < today) {
+                if (mo < 12) {
+                        mo += 1;
+                } else {
+                        mo = 1;
+                        yr += 1;
+                }
+        }
+
         seq_printf(seq, "%4.4u-", yr);
         (mo > 12) ? seq_puts(seq, "**-") : seq_printf(seq, "%2.2u-", mo);
         (day > 31) ? seq_puts(seq, "** ") : seq_printf(seq, "%2.2u ", day);