From: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu, 1 Oct 2015 22:37:16 +0000 (-0700)
Subject: thermal: avoid division by zero in power allocator
X-Git-Tag: MMI-PSA29.97-13-9~9286^2~1
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=44241628bb207ec211bebd156aaf69470d90c209;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

thermal: avoid division by zero in power allocator

During boot I get a div by zero Oops regression starting in v4.3-rc3.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Javi Merino <javi.merino@arm.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/drivers/thermal/power_allocator.c b/drivers/thermal/power_allocator.c
index 7ff96270c933..e570ff084add 100644
--- a/drivers/thermal/power_allocator.c
+++ b/drivers/thermal/power_allocator.c
@@ -144,6 +144,16 @@ static void estimate_pid_constants(struct thermal_zone_device *tz,
 		switch_on_temp = 0;
 
 	temperature_threshold = control_temp - switch_on_temp;
+	/*
+	 * estimate_pid_constants() tries to find appropriate default
+	 * values for thermal zones that don't provide them. If a
+	 * system integrator has configured a thermal zone with two
+	 * passive trip points at the same temperature, that person
+	 * hasn't put any effort to set up the thermal zone properly
+	 * so just give up.
+	 */
+	if (!temperature_threshold)
+		return;
 
 	if (!tz->tzp->k_po || force)
 		tz->tzp->k_po = int_to_frac(sustainable_power) /