linux-kernel - [PATCH] clocksource: arch_timer: Fix arm64 platforms not booting

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Date:	Sun, 28 Dec 2014 15:20:31 +0100
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	Christoffer Dall <christoffer.dall@...aro.org>,
	Sonny Rao <sonnyrao@...omium.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Mark Rutland <mark.rutland@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>
Subject: [PATCH] clocksource: arch_timer: Fix arm64 platforms not booting

Commit 0b46b8a718c6e ("clocksource: arch_timer: Fix code to...") fixes
timer issues with certain ARMv7 platforms, but unfortunately breaks
arm64 platforms with hyp mode (EL2) enabled.

The commit only sets arch_timer_use_virtual to false under CONFIG_ARM,
but forgets that the config variable is also set in other code paths
(actually, right underneath the check in the patch) with detrimental
consequences as we've now introduced a direct early call to BUG() on
practically all arm64 platforms.

One could argue that this code could be refactored to use different
variables for checking which *timer* to use and which *counter* to use,
which seems to be the desired difference between ARM and arm64 in this
case, but this approach fixes an urgent issue for now.

Cc: Sonny Rao <sonnyrao@...omium.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Olof Johansson <olof@...om.net>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Yingjoe Chen <yingjoe.chen@...iatek.com>
Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
---
This was apparently already discovered by Yingjoe Chen in this thread
https://lkml.org/lkml/2014/11/24/41 and Catalin recommended a similar
fix.

 drivers/clocksource/arm_arch_timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 6a79fc4..095c177 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -462,7 +462,7 @@ static void __init arch_counter_register(unsigned type)
 
 	/* Register the CP15 based counter if we have one */
 	if (type & ARCH_CP15_TIMER) {
-		if (arch_timer_use_virtual)
+		if (IS_ENABLED(CONFIG_ARM64) || arch_timer_use_virtual)
 			arch_timer_read_counter = arch_counter_get_cntvct;
 		else
 			arch_timer_read_counter = arch_counter_get_cntpct;
-- 
2.1.2.330.g565301e.dirty

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