RTC: Add support RTC alarms on hosted targets

Only AGPTeck Rocker is enabled for now, and it doesn't work properly:

 * No generic way to determine wakeup reason under Linux
 * No generic way to be asynchronously notified if the alarm is
   triggered when we're already awake
 * Shutting down may clobber RTC wakeup (driver/etc dependent)

And finally:

 * AGPTek kernel's RTC driver has some 24h clock and
   some timezone-related issues.

So, the infrastructure is arguably useful, but the only applicable
hardware I have is pathologically brain-dead.

Change-Id: Iac6a26a9b6e4efec5d0b3030b87f456eb23fc01d

firmware/export/config/agptekrocker.h

@@ -66,6 +66,9 @@
 /* define this if you have a real-time clock */
 #define CONFIG_RTC APPLICATION
 
+/* Define if the device can wake from an RTC alarm */
+#define HAVE_RTC_ALARM
+
 /* The number of bytes reserved for loadable codecs */
 #define CODEC_SIZE 0x80000
 

firmware/target/hosted/rtc.c

@@ -27,9 +27,14 @@
 #include <linux/rtc.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <stdbool.h>
 #endif
+
+#include "config.h"
+
 void rtc_init(void)
 {
+  tzset();
 }
 
 int rtc_read_datetime(struct tm *tm)
@@ -46,8 +51,6 @@ int rtc_write_datetime(const struct tm *tm)
     struct timeval tv;
     struct tm *tm_time;
 
-    int rtc = open("/dev/rtc0", O_WRONLY);
-
     tv.tv_sec = mktime((struct tm *)tm);
     tv.tv_usec = 0;
 
@@ -58,12 +61,147 @@ int rtc_write_datetime(const struct tm *tm)
     time_t now = time(NULL);
     tm_time = gmtime(&now);
 
-    ioctl(rtc, RTC_SET_TIME, (struct rtc_time *)tm_time);
+    /* Try to write the HW RTC, if present. */
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc > 0) {
+        ioctl(rtc, RTC_SET_TIME, (struct rtc_time *)tm_time);
+        close(rtc);
+    }
+#else
+    (void)(*tm);
+#endif
+    return 0;
+}
+
+#if defined(HAVE_RTC_ALARM) && !defined(SIMULATOR)
+void rtc_set_alarm(int h, int m)
+{
+    struct rtc_time tm;
+    long sec;
+
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc < 0)
+        return;
+
+    /* Get RTC time */
+    ioctl(rtc, RTC_RD_TIME, &tm);
+
+    /* Convert to seconds into the GMT day.  Can be negative! */
+    sec = h * 3600 + m * 60 + timezone;
+    h = sec / 3600;
+    sec -= h * 3600;
+    m = sec / 60;
+
+    /* Handle negative or positive wraps */
+    while (m < 0) {
+        m += 60;
+        h--;
+    }
+    while (m > 59) {
+        m -= 60;
+        h++;
+    }
+    while (h < 0) {
+        h += 24;
+	tm.tm_mday--;
+    }
+    while (h > 23) {
+        h -= 24;
+	tm.tm_mday++;
+    }
+
+    /* Update the struct */
+    tm.tm_sec = 0;
+    tm.tm_hour = h;
+    tm.tm_min = m;
+
+    ioctl(rtc, RTC_ALM_SET, &tm);
+    close(rtc);
+}
+
+void rtc_get_alarm(int *h, int *m)
+{
+    struct rtc_time tm;
+    long sec;
+
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc < 0)
+        return;
+
+    ioctl(rtc, RTC_ALM_READ, &tm);
     close(rtc);
 
-    return 0;
-#else
-    (void)tm;
-    return -1;
-#endif
+    /* Convert RTC from UTC to local time zone.. */
+    sec = (tm.tm_min * 60) + (tm.tm_hour * 3600) - timezone;
+
+    /* Handle wrapping and negative offsets */
+    *h = (sec / 3600);
+    sec -= *h * 3600;
+    *m = sec / 60;
+
+    while (*m < 0) {
+        *m = *m + 60;
+        *h = *h - 1;
+    }
+    while (*m > 59) {
+        *m = *m - 60;
+        *h = *h + 1;
+    }
+    while (*h < 0) {
+        *h = *h + 24;
+    }
+    while (*h > 23) {
+        *h = *h - 24;
+    }
 }
+
+void rtc_enable_alarm(bool enable)
+{
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc < 0)
+        return;
+
+    ioctl(rtc, enable ? RTC_AIE_ON : RTC_AIE_OFF, NULL);
+    close(rtc);
+
+    /* XXX Note that this may or may not work; Linux may need to be suspended
+       or shut down in a special way to keep the RTC alarm active */
+}
+
+/* Returns true if alarm was the reason we started up */
+bool rtc_check_alarm_started(bool release_alarm)
+{
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc < 0)
+        return false;
+
+    /* XXX There is no generic way of determining wakeup reason.  Will
+       likely need a target-specific hook. */
+
+    /* Disable alarm if requested */
+    if (release_alarm)
+        ioctl(rtc, RTC_AIE_OFF, NULL);
+
+    close(rtc);
+    return false;
+}
+
+/* See if we received an alarm. */
+bool rtc_check_alarm_flag(void)
+{
+    struct rtc_wkalrm alrm;
+
+    int rtc = open("/dev/rtc0", O_WRONLY);
+    if (rtc < 0)
+        return false;
+
+    alrm.pending = 0;
+    /* XXX Documented as "mostly useless on Linux" except with EFI RTCs
+       Will likely need a target-specific hook. */
+    ioctl(rtc, RTC_WKALM_RD, &alrm);
+    close(rtc);
+
+    return alrm.pending;
+}
+
+#endif /* HAVE_RTC_ALARM */