From: Marc Zyngier <marc.zyngier@arm.com>
Date: Wed, 15 Oct 2014 15:06:20 +0000 (+0100)
Subject: ARM/ARM64: arch-timer: fix arch_timer_probed logic
X-Git-Tag: v3.18-rc3~25^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=59aa896db80479dec29f471a7ca2b9eeeeb7d38e;p=linux.git

ARM/ARM64: arch-timer: fix arch_timer_probed logic

Commit c387f07e6205 (clocksource: arm_arch_timer: Discard unavailable
timers correctly) changed the way the driver makes sure both the memory
and system-register timers have been probed before finalizing the probing.

There is a interesting flaw in this logic that leads to this final step
never to be executed. Things seems to work pretty well until something
actually needs the data that is produced during this final stage.

For example, KVM explodes on the first run of a guest when executed on
a platform that has both memory and sysreg nodes (Juno, for example).

Just fix the damned logic, and enjoy booting VMs again.

Tested on a Juno system.

Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Reported-by: Riku Voipio <riku.voipio@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 2133f9d59d06..43005d4d3348 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -660,11 +660,11 @@ static bool __init
 arch_timer_probed(int type, const struct of_device_id *matches)
 {
 	struct device_node *dn;
-	bool probed = false;
+	bool probed = true;
 
 	dn = of_find_matching_node(NULL, matches);
-	if (dn && of_device_is_available(dn) && (arch_timers_present & type))
-		probed = true;
+	if (dn && of_device_is_available(dn) && !(arch_timers_present & type))
+		probed = false;
 	of_node_put(dn);
 
 	return probed;