linux-kernel - Re: [PATCH 7/8] cpufreq: mediatek: add opp notification for SVS support

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Date:   Mon, 27 May 2019 15:02:32 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        devicetree@...r.kernel.org, srv_heupstream@...iatek.com,
        linux-pm@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        fan.chen@...iatek.com, linux-mediatek@...ts.infradead.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 7/8] cpufreq: mediatek: add opp notification for SVS support

On Thu, May 16, 2019 at 9:08 AM Andrew-sh.Cheng
<andrew-sh.cheng@...iatek.com> wrote:
>         bool need_voltage_tracking;
> +       struct mutex lock; /* avoid notify and policy race condition */
> +       struct notifier_block opp_nb;
> +       int opp_cpu;
> +       unsigned long opp_freq;
>  };
>
>  static LIST_HEAD(dvfs_info_list);
> @@ -239,6 +243,7 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>         vproc = dev_pm_opp_get_voltage(opp);
>         dev_pm_opp_put(opp);
>
> +       mutex_lock(&info->lock);

Should init mutex, otherwise it'll get lockdep warning:
[    0.587055] Call trace:
[    0.587069]  dump_backtrace+0x0/0x168
[    0.587077]  show_stack+0x20/0x2c
[    0.587086]  dump_stack+0xe4/0x134
[    0.587095]  register_lock_class+0x3e8/0x4b0
[    0.587103]  __lock_acquire+0xac/0x14e8
[    0.587110]  lock_acquire+0x1d0/0x208
[    0.587118]  __mutex_lock_common+0xc0/0xb40
[    0.587126]  mutex_lock_nested+0x40/0x50
[    0.587135]  mtk_cpufreq_set_target+0xcc/0x2a8
[    0.587143]  __cpufreq_driver_target+0x438/0x4d8
[    0.587150]  cpufreq_online+0x5b4/0x6e0
[    0.587156]  cpufreq_add_dev+0x4c/0x84
[    0.587164]  subsys_interface_register+0xb8/0x10c
[    0.587171]  cpufreq_register_driver+0x11c/0x1c0
[    0.587178]  mtk_cpufreq_probe+0x378/0x4b8
[    0.587185]  platform_drv_probe+0x80/0xb0
[    0.587192]  really_probe+0x114/0x28c
[    0.587198]  driver_probe_device+0x64/0xfc
[    0.587205]  __device_attach_driver+0xb8/0xd0
[    0.587211]  bus_for_each_drv+0x88/0xd0
[    0.587218]  __device_attach+0xb0/0x134
[    0.587224]  device_initial_probe+0x20/0x2c
[    0.587230]  bus_probe_device+0x34/0x94
[    0.587238]  device_add+0x520/0x5b4
[    0.587245]  platform_device_add+0x17c/0x208
[    0.587252]  platform_device_register_full+0xc0/0x100
[    0.587261]  mtk_cpufreq_driver_init+0x8c/0xdc
[    0.587268]  do_one_initcall+0x1c0/0x3e0
[    0.587276]  do_initcall_level+0x1f4/0x224
[    0.587282]  do_basic_setup+0x34/0x4c
[    0.587288]  kernel_init_freeable+0x10c/0x194
[    0.587295]  kernel_init+0x14/0x100
[    0.587302]  ret_from_fork+0x10/0x18
[    0.587510] cpufreq: cpufreq_online: CPU4: Unlisted initial
frequency changed to: 1248000 KHz