1 files changed, 93 insertions, 0 deletions
diff --git a/qemu/roms/seabios/src/hw/rtc.c b/qemu/roms/seabios/src/hw/rtc.c
new file mode 100644
index 000000000..628d5429f
--- /dev/null
+++ b/qemu/roms/seabios/src/hw/rtc.c
@@ -0,0 +1,93 @@
+// Support for MC146818 Real Time Clock chip.
+//
+// Copyright (C) 2008-2013  Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2002  MandrakeSoft S.A.
+//
+// This file may be distributed under the terms of the GNU LGPLv3 license.
+
+#include "biosvar.h" // GET_LOW
+#include "rtc.h" // rtc_read
+#include "stacks.h" // yield
+#include "util.h" // timer_calc
+#include "x86.h" // inb
+
+u8
+rtc_read(u8 index)
+{
+    index |= NMI_DISABLE_BIT;
+    outb(index, PORT_CMOS_INDEX);
+    return inb(PORT_CMOS_DATA);
+}
+
+void
+rtc_write(u8 index, u8 val)
+{
+    index |= NMI_DISABLE_BIT;
+    outb(index, PORT_CMOS_INDEX);
+    outb(val, PORT_CMOS_DATA);
+}
+
+void
+rtc_mask(u8 index, u8 off, u8 on)
+{
+    outb(index, PORT_CMOS_INDEX);
+    u8 val = inb(PORT_CMOS_DATA);
+    outb((val & ~off) | on, PORT_CMOS_DATA);
+}
+
+int
+rtc_updating(void)
+{
+    // This function checks to see if the update-in-progress bit
+    // is set in CMOS Status Register A.  If not, it returns 0.
+    // If it is set, it tries to wait until there is a transition
+    // to 0, and will return 0 if such a transition occurs.  A -1
+    // is returned only after timing out.  The maximum period
+    // that this bit should be set is constrained to (1984+244)
+    // useconds, but we wait for longer just to be sure.
+
+    if ((rtc_read(CMOS_STATUS_A) & RTC_A_UIP) == 0)
+        return 0;
+    u32 end = timer_calc(15);
+    for (;;) {
+        if ((rtc_read(CMOS_STATUS_A) & RTC_A_UIP) == 0)
+            return 0;
+        if (timer_check(end))
+            // update-in-progress never transitioned to 0
+            return -1;
+        yield();
+    }
+}
+
+void
+rtc_setup(void)
+{
+    rtc_write(CMOS_STATUS_A, 0x26);    // 32,768Khz src, 976.5625us updates
+    rtc_mask(CMOS_STATUS_B, ~RTC_B_DSE, RTC_B_24HR);
+    rtc_read(CMOS_STATUS_C);
+    rtc_read(CMOS_STATUS_D);
+}
+
+int RTCusers VARLOW;
+
+void
+rtc_use(void)
+{
+    int count = GET_LOW(RTCusers);
+    SET_LOW(RTCusers, count+1);
+    if (count)
+        return;
+    // Turn on the Periodic Interrupt timer
+    rtc_mask(CMOS_STATUS_B, 0, RTC_B_PIE);
+}
+
+void
+rtc_release(void)
+{
+    int count = GET_LOW(RTCusers);
+    SET_LOW(RTCusers, count-1);
+    if (count != 1)
+        return;
+    // Clear the Periodic Interrupt.
+    rtc_mask(CMOS_STATUS_B, RTC_B_PIE, 0);
+}