linux-kernel - Re: [PATCH v12 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver

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Date:   Wed, 19 Dec 2018 11:14:42 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Taniya Das <tdas@...eaurora.org>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Rajendra Nayak <rnayak@...eaurora.org>,
        devicetree@...r.kernel.org, robh@...nel.org,
        skannan@...eaurora.org, linux-arm-msm@...r.kernel.org,
        evgreen@...gle.com, Matthias Kaehlcke <mka@...omium.org>,
        vincent.guittot@...aro.org
Subject: Re: [PATCH v12 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq
 HW driver

On 18-12-18, 11:13, Stephen Boyd wrote:
> I don't see any failure returned from cpufreq_dt's cpufreq_init()
> function. Maybe put a static int counter = 0 and then fail
> cpufreq_init() the second time that it's called for the same policy
> pointer? I have a system with two policies, so I made it fail and return
> -EINVAL when the counter == 2 and I see the lockdep splat.

Yuck. You were so clear on this earlier, how can I forget it. :(

Here is the additional diff. And I do get this print message on my screen while
I try to online CPU4.

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index 639feca22d27..b836e93fd87d 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -151,6 +151,11 @@ static int cpufreq_init(struct cpufreq_policy *policy)
        const char *name;
        int ret;
 
+       if (policy->count++) {
+               pr_info("%s: %d\n", __func__, __LINE__);
+               return -EINVAL;
+       }
+
        cpu_dev = get_cpu_device(policy->cpu);
        if (!cpu_dev) {
                pr_err("failed to get cpu%d device\n", policy->cpu);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 882a9b9e34bc..643141a2013f 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -151,6 +151,7 @@ struct cpufreq_policy {
 
        /* For cpufreq driver's internal use */
        void                    *driver_data;
+       int                     count;
 };

> I did the following:
> 
>   grep . /sys/devices/system/cpu/cpufreq/*/* >/dev/null
>   echo 0 > /sys/devices/system/cpu/cpu4/online 
>   echo 0 > /sys/devices/system/cpu/cpu5/online 
>   echo 0 > /sys/devices/system/cpu/cpu6/online 
>   echo 0 > /sys/devices/system/cpu/cpu7/online 
>   echo 1 > /sys/devices/system/cpu/cpu4/online 
>   dmesg
> 
> And boom, lockdep splat.

  502  grep . /sys/devices/system/cpu/cpufreq/*/*
  503  echo 0 > /sys/devices/system/cpu/cpu4/online
  504  echo 0 > /sys/devices/system/cpu/cpu5/online
  505  echo 0 > /sys/devices/system/cpu/cpu6/online
  506  echo 0 > /sys/devices/system/cpu/cpu7/online
  507  grep . /sys/devices/system/cpu/cpufreq/*/*
  508  echo 1 > /sys/devices/system/cpu/cpu4/online
  509  dmesg 


But still no lockdep :(

Can you try that on mainline as well ?

-- 
viresh