From 7970e08bf066900efcd7794a1a338c11eb8f5141 Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Thu, 13 Apr 2006 15:14:04 +0200 Subject: [PATCH] [CPUFREQ] If max_freq got reduced (e.g. by _PPC) a write to sysfs scaling_governor let cpufreq core stuck at low max_freq for ever The previous patch had bugs (locking and refcount). This one could also be related to the latest DELL reports. But they only slip into this if a user prog (e.g. powersave daemon does when AC got (un) plugged due to a scheme change) echos something to /sys/../cpufreq/scaling_governor while the frequencies got limited by BIOS. This one works: Subject: Max freq stucks at low freq if reduced by _PPC and sysfs gov access The problem is reproducable by(if machine is limiting freqs via BIOS): - Unplugging AC -> max freq gets limited - echo ${governor} >/sys/.../cpufreq/scaling_governor (policy->user_data.max gets overridden with policy->max and will never come up again.) This patch exchanged the cpufreq_set_policy call to __cpufreq_set_policy and duplicated it's functionality but did not override user_data.max. The same happens with overridding min/max values. If freqs are limited and you override the min freq value, the max freq global value will also get stuck to the limited freq, even if BIOS allows all freqs again. Last scenario does only happen if BIOS does not reduce the frequency to the lowest value (should never happen, just for correctness...) drivers/cpufreq/cpufreq.c | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) Signed-off-by: Thomas Renninger Signed-off-by: "Pallipadi, Venkatesh" Signed-off-by: Dave Jones --- drivers/cpufreq/cpufreq.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 3d0430741b5a..12e63642aa0f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -346,6 +346,8 @@ show_one(scaling_min_freq, min); show_one(scaling_max_freq, max); show_one(scaling_cur_freq, cur); +static int __cpufreq_set_policy(struct cpufreq_policy *data, struct cpufreq_policy *policy); + /** * cpufreq_per_cpu_attr_write() / store_##file_name() - sysfs write access */ @@ -364,7 +366,10 @@ static ssize_t store_##file_name \ if (ret != 1) \ return -EINVAL; \ \ - ret = cpufreq_set_policy(&new_policy); \ + mutex_lock(&policy->lock); \ + ret = __cpufreq_set_policy(policy, &new_policy); \ + policy->user_policy.object = policy->object; \ + mutex_unlock(&policy->lock); \ \ return ret ? ret : count; \ } @@ -420,7 +425,15 @@ static ssize_t store_scaling_governor (struct cpufreq_policy * policy, if (cpufreq_parse_governor(str_governor, &new_policy.policy, &new_policy.governor)) return -EINVAL; - ret = cpufreq_set_policy(&new_policy); + /* Do not use cpufreq_set_policy here or the user_policy.max + will be wrongly overridden */ + mutex_lock(&policy->lock); + ret = __cpufreq_set_policy(policy, &new_policy); + + policy->user_policy.policy = policy->policy; + policy->user_policy.governor = policy->governor; + mutex_unlock(&policy->lock); + return ret ? ret : count; } -- 2.30.2