[coreboot] New patch to review for coreboot: 2c2e4a1 RTC: Don't clear pending interrupt in resume path

Stefan Reinauer (stefan.reinauer@coreboot.org) gerrit at coreboot.org
Wed Nov 7 00:50:27 CET 2012

Stefan Reinauer (stefan.reinauer at coreboot.org) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/1741


commit 2c2e4a14a302644acb615d9858f2d6b651b80062
Author: Duncan Laurie <dlaurie at chromium.org>
Date:   Wed Sep 5 10:52:44 2012 -0700

    RTC: Don't clear pending interrupt in resume path
    The linux kernel relies on the RTC reporting pending interrupts if
    the RTC alarm was used to wake the system.  If we clear these flags
    here then the rtc-cmos driver in the kernel will think that no
    interrupts are pending and will not re-start the timerqueue to
    handle the alarm timerqueue node.
    This flag doesn't exist in SMM but the rtc code is compiled there.
    Since rtc_init() is not called by SMM it is guarded with an ifdef.
    I performed several thousand suspend/resume cycles without seeing
    an issue where hwclock was unable to read from /dev/rtc.  There
    still is a potential kernel issue where the timerqueue can stall
    but this makes that much less likely to happen on resume.
    Change-Id: I5a343da4ce5c4c8ec4783b4e503869ccfa5077f0
    Signed-off-by: Duncan Laurie <dlaurie at chromium.org>
 src/drivers/pc80/mc146818rtc.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/drivers/pc80/mc146818rtc.c b/src/drivers/pc80/mc146818rtc.c
index 52cfb63..6e5b92a 100644
--- a/src/drivers/pc80/mc146818rtc.c
+++ b/src/drivers/pc80/mc146818rtc.c
@@ -8,6 +8,9 @@
 #include "option_table.h"
 #include <cbfs.h>
+#include <arch/acpi.h>
 /* control registers - Moto names
@@ -127,6 +130,7 @@ static void rtc_set_checksum(int range_start, int range_end, int cks_loc)
+#ifndef __SMM__
 void rtc_init(int invalid)
 	int cmos_invalid = 0;
@@ -192,9 +196,20 @@ void rtc_init(int invalid)
+	/*
+	 * Avoid clearing pending interrupts in the resume path because
+	 * the Linux kernel relies on this to know if it should restart
+	 * the RTC timerqueue if the wake was due to the RTC alarm.
+	 */
+	if (acpi_slp_type == 3)
+		return;
 	/* Clear any pending interrupts */
 	(void) cmos_read(RTC_INTR_FLAGS);

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