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* [PATCH 4.19 143/639] rtc: cmos: ignore bogus century byte
       [not found] <20200124093047.008739095@linuxfoundation.org>
@ 2020-01-24  9:25 ` Greg Kroah-Hartman
  2020-01-25 12:04   ` Pavel Machek
  0 siblings, 1 reply; 2+ messages in thread
From: Greg Kroah-Hartman @ 2020-01-24  9:25 UTC (permalink / raw)
  To: linux-kernel
  Cc: Greg Kroah-Hartman, stable, Alexandre Belloni, Alessandro Zummo,
	Sylvain Chouleur, Patrick McDermott, linux-rtc, Eric Wong,
	Sasha Levin

From: Eric Wong <e@80x24.org>

[ Upstream commit 2a4daadd4d3e507138f8937926e6a4df49c6bfdc ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 2f1772a358ca5..18a6f15e313d8 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;
 
 	/*
-- 
2.20.1




^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH 4.19 143/639] rtc: cmos: ignore bogus century byte
  2020-01-24  9:25 ` [PATCH 4.19 143/639] rtc: cmos: ignore bogus century byte Greg Kroah-Hartman
@ 2020-01-25 12:04   ` Pavel Machek
  0 siblings, 0 replies; 2+ messages in thread
From: Pavel Machek @ 2020-01-25 12:04 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: linux-kernel, stable, Alexandre Belloni, Alessandro Zummo,
	Sylvain Chouleur, Patrick McDermott, linux-rtc, Eric Wong,
	Sasha Levin

[-- Attachment #1: Type: text/plain, Size: 669 bytes --]

Hi!

> From: Eric Wong <e@80x24.org>
> 
> [ Upstream commit 2a4daadd4d3e507138f8937926e6a4df49c6bfdc ]
> 
> 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.

Should it print a warning so that wrong BIOSes are eventually fixed?

Best regards,
								Pavel
								
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[-- Attachment #2: signature.asc --]
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^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-01-24  9:25 ` [PATCH 4.19 143/639] rtc: cmos: ignore bogus century byte Greg Kroah-Hartman
2020-01-25 12:04   ` Pavel Machek

Linux-RTC Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-rtc/0 linux-rtc/git/0.git

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	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-rtc linux-rtc/ https://lore.kernel.org/linux-rtc \
		linux-rtc@vger.kernel.org
	public-inbox-index linux-rtc

Example config snippet for mirrors

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