Message-ID: <574678D0.1080301@rock-chips.com>
Date:	Thu, 26 May 2016 12:17:20 +0800
From:	Caesar Wang <wxt@...k-chips.com>
To:	Javi Merino <javi.merino@....com>
CC:	huangtao@...k-chips.com, Jonathan Corbet <corbet@....net>,
	Ni Wade <wni@...dia.com>, Heiko Stuebner <heiko@...ech.de>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sascha Hauer <s.hauer@...gutronix.de>,
	dmitry.torokhov@...il.com, peter@...e.net, dianders@...omium.org,
	linux-doc@...r.kernel.org, edubezval@...il.com,
	linux-rockchip@...ts.infradead.org,
	Laxman Dewangan <ldewangan@...dia.com>, smbarber@...gle.com,
	Leo Yan <leo.yan@...aro.org>, cf@...k-chips.com,
	briannorris@...gle.com, Zhang Rui <rui.zhang@...el.com>,
	Andy Champ <andycham@...zon.com>
Subject: Re: [PATCH v3 1/5] thermal: Add support for hardware-tracked trip
 points


On 2016年05月26日 08:34, Caesar Wang wrote:
>
> On 2016年05月26日 00:42, Javi Merino wrote:
>> Hi Caesar,
>>
>> On Wed, May 25, 2016 at 11:47:45AM +0800, Caesar Wang wrote:
>>> From: Sascha Hauer <s.hauer@...gutronix.de>
>>>
>>> This adds support for hardware-tracked trip points to the device tree
>>> thermal sensor framework.
>>>
>>> The framework supports an arbitrary number of trip points. Whenever
>>> the current temperature is updated, the trip points immediately
>>> below and above the current temperature are found. A .set_trips
>>> callback is then called with the temperatures. If there is no trip
>>> point above or below the current temperature, the passed trip
>>> temperature will be -INT_MAX or INT_MAX respectively. In this callback,
>>> the driver should program the hardware such that it is notified
>>> when either of these trip points are triggered. When a trip point
>>> is triggered, the driver should call `thermal_zone_device_update'
>>> for the respective thermal zone. This will cause the trip points
>>> to be updated again.
>>>
>>> If .set_trips is not implemented, the framework behaves as before.
>>>
>>> This patch is based on an earlier version from Mikko Perttunen
>>> <mikko.perttunen@...si.fi>
>>>
>>> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
>>> Signed-off-by: Caesar Wang <wxt@...k-chips.com>
>>> Cc: Zhang Rui <rui.zhang@...el.com>
>>> Cc: Eduardo Valentin <edubezval@...il.com>
>>> Cc: linux-pm@...r.kernel.org
>>>
>>> ---
>>>
>>> Changes in v3:
>>> - as Javi comments on https://patchwork.kernel.org/patch/9001281/.
>>> - add the lock for preventing the called from multi placce
>>> - add the note for pre_low/high_trip.
>>>
>>> Changes in v2:
>>> - update the sysfs-api.txt for set_trips.
>>>
>>>   Documentation/thermal/sysfs-api.txt |  7 +++++
>>>   drivers/thermal/thermal_core.c      | 52 
>>> +++++++++++++++++++++++++++++++++++++
>>>   include/linux/thermal.h             |  7 +++++
>>>   3 files changed, 66 insertions(+)
>>>
>>> diff --git a/Documentation/thermal/sysfs-api.txt 
>>> b/Documentation/thermal/sysfs-api.txt
>>> index efc3f3d..75d8838 100644
>>> --- a/Documentation/thermal/sysfs-api.txt
>>> +++ b/Documentation/thermal/sysfs-api.txt
>>> @@ -49,6 +49,9 @@ temperature) and throttle appropriate devices.
>>>       .bind: bind the thermal zone device with a thermal cooling 
>>> device.
>>>       .unbind: unbind the thermal zone device with a thermal cooling 
>>> device.
>>>       .get_temp: get the current temperature of the thermal zone.
>>> +    .set_trips: set the trip points window. Whenever the current 
>>> temperature
>>> +            is updated, the trip points immediately below and above 
>>> the
>>> +            current temperature are found.
>>>       .get_mode: get the current mode (enabled/disabled) of the 
>>> thermal zone.
>>>           - "enabled" means the kernel thermal management is enabled.
>>>           - "disabled" will prevent kernel thermal driver action 
>>> upon trip points
>>> @@ -95,6 +98,10 @@ temperature) and throttle appropriate devices.
>>>               get_temp:    a pointer to a function that reads the
>>>                       sensor temperature. This is mandatory
>>>                       callback provided by sensor driver.
>>> +            set_trips:      a pointer to a function that sets a
>>> +                    temperature window. When this window is
>>> +                    left the driver must inform the thermal
>>> +                    core via thermal_zone_device_update.
>>>               get_trend:     a pointer to a function that reads the
>>>                       sensor temperature trend.
>>>               set_emul_temp:    a pointer to a function that sets
>>> diff --git a/drivers/thermal/thermal_core.c 
>>> b/drivers/thermal/thermal_core.c
>>> index 5133cd1..e5bfbd3 100644
>>> --- a/drivers/thermal/thermal_core.c
>>> +++ b/drivers/thermal/thermal_core.c
>>> @@ -520,6 +520,51 @@ exit:
>>>   }
>>>   EXPORT_SYMBOL_GPL(thermal_zone_get_temp);
>>>   +static void thermal_zone_set_trips(struct thermal_zone_device *tz)
>>> +{
>>> +    int low = -INT_MAX;
>>> +    int high = INT_MAX;
>>> +    int trip_temp, hysteresis;
>>> +    int temp = tz->temperature;
>>> +    int i, ret;
>>> +
>>> +    if (!tz->ops->set_trips)
>>> +        return;
>>> +
>>> +    for (i = 0; i < tz->trips; i++) {
>>> +        int trip_low;
>>> +
>>> +        tz->ops->get_trip_temp(tz, i, &trip_temp);
>>> +        tz->ops->get_trip_hyst(tz, i, &hysteresis);
>>> +
>>> +        trip_low = trip_temp - hysteresis;
>>> +
>>> +        if (trip_low < temp && trip_low > low)
>>> +            low = trip_low;
>>> +
>>> +        if (trip_temp > temp && trip_temp < high)
>>> +            high = trip_temp;
>>> +    }
>>> +
>>> +    /* No need to change trip points */
>>> +    if (tz->prev_low_trip == low && tz->prev_high_trip == high)
>>> +        return;
>>> +
>>> +    tz->prev_low_trip = low;
>>> +    tz->prev_high_trip = high;
>>> +
>>> +    dev_dbg(&tz->device, "new temperature boundaries: %d < x < %d\n",
>>> +            low, high);
>>> +
>>> +    /*
>>> +     * Set a temperature window. When this window is left the driver
>>> +     * must inform the thermal core via thermal_zone_device_update.
>>> +     */
>>> +    ret = tz->ops->set_trips(tz, low, high);
>>> +    if (ret)
>>> +        dev_err(&tz->device, "Failed to set trips: %d\n", ret);
>> In the v2 review
>> (http://article.gmane.org/gmane.linux.documentation/38442) you agreed
>> to add locking but you haven't done it.  Maybe you sent the wrong
>> version?
>
> My god!
> Yep, I remember to change it. Somehow why ...
>
> Thanks Javi for looking over it.
>
> Hoping the next version is the final version.:-)
>

If add the lock, there is a deadlock for board,  maybe I will keep to 
stay with this version.

   2.895038] [ INFO: possible recursive locking detected ]
[    2.900459] 4.4.4 #56 Not tainted
[    2.903774] ---------------------------------------------
[    2.909171] swapper/0/1 is trying to acquire lock:
[    2.913974]  (&tz->lock){+.+.+.}, at: [<ffffffc00069b428>] 
handle_thermal_trip+0x230/0x304
[    2.922336]
[    2.922336] but task is already holding lock:
[    2.928166]  (&tz->lock){+.+.+.}, at: [<ffffffc000699194>] 
thermal_zone_set_trips+0xd8/0x180
[    2.936670]
[    2.936670] other info that might help us debug this:
[    2.943199]  Possible unsafe locking scenario:
[    2.943199]
[    2.949117]        CPU0
[    2.951565]        ----
[    2.954012]   lock(&tz->lock);
[    2.957098]   lock(&tz->lock);
[    2.960176]
[    2.960176]  *** DEADLOCK ***
[    2.960176]
[    2.966098]  May be due to missing lock nesting notation
[    2.966098]
[    2.972885] 3 locks held by swapper/0/1:
[    2.976809]  #0:  (&dev->mutex){......}, at: [<ffffffc0005920b0>] 
__driver_attach+0x40/0xa8
[    2.985243]  #1:  (&dev->mutex){......}, at: [<ffffffc0005920d8>] 
__driver_attach+0x68/0xa8
[    2.993671]  #2:  (&tz->lock){+.+.+.}, at: [<ffffffc000699194>] 
thermal_zone_set_trips+0xd8/0x180
...







> -Caesar
>
>>
>> Cheers,
>> Javi
>>
>> _______________________________________________
>> Linux-rockchip mailing list
>> Linux-rockchip@...ts.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>
>

-- 
caesar wang | software engineer | wxt@...k-chip.com

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