Re: [PATCH v3 1/5] thermal: Add support for hardware-tracked trip points

From: Caesar Wang
Date: Thu May 26 2016 - 00:17:55 EST


On 2016å05æ26æ 08:34, Caesar Wang wrote:

On 2016å05æ26æ 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@xxxxxxxxxxxxxx>

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@xxxxxxxx>

Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx>
Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
Cc: Eduardo Valentin <edubezval@xxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx

---

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

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--
caesar wang | software engineer | wxt@xxxxxxxxxxxxx