Re: [RFC PATCH 2/2] thermal: add a virtual sensor to aggregate temperatures

From: Alexandre Bailon
Date: Mon Aug 23 2021 - 03:53:10 EST

Hi Daniel,

On 20/08/2021 14:52, Daniel wrote:
On 19/08/2021 14:32, Alexandre Bailon wrote:
This adds a virtual thermal sensor that reads temperature from
hardware sensor and return an aggregated temperature.
Currently, this only return the max temperature.

Signed-off-by: Alexandre Bailon <abailon@xxxxxxxxxxxx>
---
drivers/thermal/Kconfig | 8 ++
drivers/thermal/Makefile | 1 +
drivers/thermal/thermal_aggregator.c | 134 +++++++++++++++++++++++++++
3 files changed, 143 insertions(+)
create mode 100644 drivers/thermal/thermal_aggregator.c

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 7a4ba50ba97d0..f9c152cfb95bc 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -228,6 +228,14 @@ config THERMAL_MMIO
register or shared memory, is a potential candidate to work with this
driver.
+config THERMAL_AGGREGATOR
We discussed the virtual sensor doing aggregation but may be we can give
it another purpose in the future like returning a constant temp or
low/high pass filter.

It may make sense to use a more generic name like virtual sensor for
example.
Indeed, this would make more sense.

+ tristate "Generic thermal aggregator driver"
+ depends on TERMAL_OF || COMPILE_TEST
s/TERMAL_OF/THERMAL_OF/

+ help
+ This option enables the generic thermal sensor aggregator.
+ This driver creates a thermal sensor that reads the hardware sensors
+ and aggregate the temperature.
+
config HISI_THERMAL
tristate "Hisilicon thermal driver"
depends on ARCH_HISI || COMPILE_TEST
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 9729a2b089919..5b20ef15aebbe 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -60,3 +60,4 @@ obj-$(CONFIG_UNIPHIER_THERMAL) += uniphier_thermal.o
obj-$(CONFIG_AMLOGIC_THERMAL) += amlogic_thermal.o
obj-$(CONFIG_SPRD_THERMAL) += sprd_thermal.o
obj-$(CONFIG_KHADAS_MCU_FAN_THERMAL) += khadas_mcu_fan.o
+obj-$(CONFIG_THERMAL_AGGREGATOR) += thermal_aggregator.o
diff --git a/drivers/thermal/thermal_aggregator.c b/drivers/thermal/thermal_aggregator.c
new file mode 100644
index 0000000000000..76f871dbfee9e
--- /dev/null
+++ b/drivers/thermal/thermal_aggregator.c
@@ -0,0 +1,134 @@
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <linux/thermal.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+const char *aggr_types[] = {
+ "min",
+ "max",
+ "avg",
+};
+
+struct thermal_aggr;
+
+typedef int (*aggregate_fn)(struct thermal_aggr *aggr);
+
+struct thermal_aggr_sensor {
+ struct thermal_sensor *sensor;
+
+ struct list_head node;
+};
+
+struct thermal_aggr {
+ struct list_head sensors;
+ aggregate_fn *aggregate;
+ //struct thermal_zone_device *tz;
+};
+
+static int thermal_aggr_read_temp(void *data, int *temperature)
+{
+ struct thermal_aggr *aggr = data;
+ struct thermal_aggr_sensor *sensor;
+ int max_temp = 0;
+ int temp;
+
What happens if a hardware sensor module is unloaded ?
Hum, I don't know how to deal with it.
Maybe adding refcounting to sensors to prevent module unloading ?

+ list_for_each_entry(sensor, &aggr->sensors, node) {
+ if (!sensor->sensor) {
+ return -ENODEV;
+ }



+ sensor->sensor->ops->get_temp(sensor->sensor->sensor_data, &temp);
+ max_temp = max(max_temp, temp);
+ }
+
+ *temperature = max_temp;
+
+ return 0;
+}
+
+static const struct thermal_zone_of_device_ops thermal_aggr_max_ops = {
+ .get_temp = thermal_aggr_read_temp,
.get_temp = thermal_virtual_sensor_get_temp ?

Actually, I though I could create a thermol_zone_of_device_ops for each type of operation
(min, max, etc) we would support and would just to register the right ops at probe time.

+};
+
+static int thermal_aggr_probe(struct platform_device *pdev)
+{
+ struct thermal_aggr *aggr;
+ struct device *dev = &pdev->dev;
+ struct of_phandle_args args;
+ int count;
+ int ret;
+ int i;
+
+ count = of_count_phandle_with_args(dev->of_node,
+ "thermal-sensors",
+ "#thermal-sensor-cells");
+ if (count <= 0)
+ return -EINVAL;
+
+ aggr = kzalloc(sizeof(*aggr), GFP_KERNEL);
devm_kzalloc

+ INIT_LIST_HEAD(&aggr->sensors);
+
+ for (i = 0; i < count; i++) {
+ struct thermal_sensor *sensor;
+ struct thermal_aggr_sensor *aggr_sensor;
+ int id;
+
+ ret = of_parse_phandle_with_args(dev->of_node,
+ "thermal-sensors",
+ "#thermal-sensor-cells",
+ i,
+ &args);
+ if (ret) {
+ return ret;
+ }
+
+ id = args.args_count ? args.args[0] : 0;
+ sensor = thermal_of_get_sensor(args.np, id);
+ if (sensor == NULL) {
+ return -EPROBE_DEFER;
+ }
+
+ aggr_sensor = kzalloc(sizeof(*aggr_sensor), GFP_KERNEL);
devm_kzalloc

+ aggr_sensor->np = args.np;
Why the 'np' and id are stored, they won't be needed anymore, no ?
Right. At some point, I had issues with the sensors that was not available.
I though it was an probe orderings issue and I tried to get the sensor later from the callback.
It was an issue with the sensor module itself, and not with the ordering but I forgot to remove
np and id that not useful anymore.

+ aggr_sensor->id = id;
+ aggr_sensor->sensor = sensor;
+ list_add(&aggr_sensor->node, &aggr->sensors);
+ }
+
+ /*tzdev = */devm_thermal_zone_of_sensor_register(dev, 0, aggr, &thermal_aggr_max_ops);
+
+ return 0;
+}
+
+static int thermal_aggr_remove(struct platform_device *pdev)
+{
+ return 0;
+}
+
+static const struct of_device_id thermal_aggr_of_match[] = {
+ {
+ .compatible = "generic,thermal-aggregator", "^virtual,.*":
As stated in the documentation
Documentation/devicetree/bindings/vendor-prefixes.yaml

"^virtual,.*":
description: Used for virtual device without specific vendor.

I suggest something like:

.compatible = "virtual,thermal-sensor",
OK, makes sense to me.

Thanks you for the review.
Alexandre



+ },
+ {
+ },
+};
+MODULE_DEVICE_TABLE(of, thermal_aggr_of_match);
+
+static struct platform_driver thermal_aggr = {
+ .probe = thermal_aggr_probe,
+ .remove = thermal_aggr_remove,
+ .driver = {
+ .name = "thermal-aggregator",
+ .of_match_table = thermal_aggr_of_match,
+ },
+};
+
+module_platform_driver(thermal_aggr);
+MODULE_AUTHOR("Alexandre Bailon <abailon@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Thermal sensor aggregator");
+MODULE_LICENSE("GPL v2");