linux-kernel - [PATCH] cpufreq: longhaul: Set transition_delay

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Date:   Tue, 28 Nov 2017 08:41:30 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rafael Wysocki <rjw@...ysocki.net>, mroos@...ux.ee
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "4 . 14+" <stable@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] cpufreq: longhaul: Set transition_delay_us to 20 ms

The commit e948bc8fbee0 ("cpufreq: Cap the default transition delay
value to 10 ms") caused a regression on EPIA-M min-ITX computer where
shutdown or reboot hangs occasionally with a print message like:

longhaul: Warning: Timeout while waiting for idle PCI bus
cpufreq: __target_index: Failed to change cpu frequency: -16

This probably happens because the cpufreq governor tries to change the
frequency of the CPU faster than allowed by the hardware.

With the above commit, the default transition delay comes to 10 ms for a
transition_latency of 200 us. Set the default transition delay to 20 ms
directly to fix this regression.

Fixes: e948bc8fbee0 ("cpufreq: Cap the default transition delay value to 10 ms")
Cc: 4.14+ <stable@...r.kernel.org> # 4.14+
Reported-by: Meelis Roos <mroos@...ux.ee>
Suggested-by: Rafael J. Wysocki <rjw@...ysocki.net>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/longhaul.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/longhaul.c b/drivers/cpufreq/longhaul.c
index c46a12df40dd..56eafcb07859 100644
--- a/drivers/cpufreq/longhaul.c
+++ b/drivers/cpufreq/longhaul.c
@@ -894,7 +894,7 @@ static int longhaul_cpu_init(struct cpufreq_policy *policy)
 	if ((longhaul_version != TYPE_LONGHAUL_V1) && (scale_voltage != 0))
 		longhaul_setup_voltagescaling();
 
-	policy->cpuinfo.transition_latency = 200000;	/* nsec */
+	policy->transition_delay_us = 20000;	/* usec */
 
 	return cpufreq_table_validate_and_show(policy, longhaul_table);
 }
-- 
2.15.0.194.g9af6a3dea062