patches: Add RTC century byte fix

2 files changed, 40 insertions, 0 deletions

diff --git a/changelog b/changelog
index 40ac598..9775ac2 100644
--- a/changelog
+++ b/changelog
@@ -6,6 +6,9 @@ linux-libre-4.19 (4.19.56+gnu-1) trunk
   * Update Maintainer and Homepage.
   * Regenerate M+ fonts from M+ version 063a using otf2bdf and bdf2fbcon and
     rebase patch onto new upstream Linux-libre.
+  * Apply patch from Eric Wong to fix regression in Linux(-libre) >= 4.3 with
+    older versions of libreboot and coreboot that didn't reserve the RTC
+    century byte in NVRAM/CMOS.
 
  -- Patrick McDermott <patrick.mcdermott@libiquity.com>  Fri, 28 Jun 2019 18:50:56 -0400
 
diff --git a/patches/02_rtc-cmos-ignore-bogus-century-byte.patch b/patches/02_rtc-cmos-ignore-bogus-century-byte.patch
new file mode 100644
index 0000000..904d61f
--- /dev/null
+++ b/patches/02_rtc-cmos-ignore-bogus-century-byte.patch
@@ -0,0 +1,37 @@
+From 2a4daadd4d3e507138f8937926e6a4df49c6bfdc Mon Sep 17 00:00:00 2001
+From: Eric Wong <e@80x24.org>
+Date: Sun, 6 Jan 2019 08:21:03 +0000
+Subject: rtc: cmos: ignore bogus century byte
+
+Older versions of Libreboot and Coreboot had an invalid value
+(`3' in my case) in the century byte affecting the GM45 in
+the Thinkpad X200.  Not everybody's updated their firmwares,
+and Linux <= 4.2 was able to read the RTC without problems,
+so workaround this by ignoring invalid values.
+
+Fixes: 3c217e51d8a272b9 ("rtc: cmos: century support")
+
+Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
+Cc: Alessandro Zummo <a.zummo@towertech.it>
+Cc: Sylvain Chouleur <sylvain.chouleur@intel.com>
+Cc: Patrick McDermott <patrick.mcdermott@libiquity.com>
+Cc: linux-rtc@vger.kernel.org
+Signed-off-by: Eric Wong <e@80x24.org>
+Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
+---
+ drivers/rtc/rtc-mc146818-lib.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
+index 2f1772a358ca..18a6f15e313d 100644
+--- a/drivers/rtc/rtc-mc146818-lib.c
++++ b/drivers/rtc/rtc-mc146818-lib.c
+@@ -82,7 +82,7 @@ unsigned int mc146818_get_time(struct rtc_time *time)
+ 	time->tm_year += real_year - 72;
+ #endif
+ 
+-	if (century)
++	if (century > 20)
+ 		time->tm_year += (century - 19) * 100;
+ 
+ 	/*