On Fri, Jan 22, 2016 at 06:53:50PM -0800, Guenter Roeck wrote: > The thermal subsystem supports setting trip points, which I would think > is what you are looking for here. Question is if an how you can use the > information from the thermal subsystem (and thus the thermal zone configuration) > to set the various limits in the lm90 driver. This should hopefully be sufficient > to fix your immediate problem. For handling alerts, I guess we'll have to wait for > thermal subsystem improvements (unless of course you volunteer to do that work. I may take a shot at this. So in short, the goal is to have a device tree thermal zone communicate trip points to the sensor driver, and use interrupts to act on trips. (This indirectly solves my problem of my sensor having weird initial values. Perhaps we also want a solution for this case if the thermal subsystem is disabled, but for me there'd be no need.) Here's what I see: - The thermal core layer already supports interrupt driven systems. Support is missing from thermal OF, the layer between thermal core and the sensor driver implementing device tree support. - Thermal OF registers a device in thermal core for each zone defined in the device tree. - In theory, a thermal zone in the device tree can have multiple sensors, and multiple zones can refer to the same sensor, but the current implementation only supports 1-on-1 relations. - There are already exports thermal_zone_device_update and thermal_notify_framework in thermal core, which allow external code to trigger an update. - Updates happen by explicit calls to such exports, or by an optional and configurable interval in thermal core. What I think we want: - Any additions should be optional extensions implemented by sensor drivers. Polling should keep on working for all sensor drivers already supporting thermal OF, with no interface changes. - For interrupt-capable sensor drivers, the thermal OF device should keep the sensor driver updated with the current nearest trip temperature and hysteresis. (Don't burden drivers with a full list of trip points.) - In the case of LM90, this would set the low and high alert temperatures. LM90 can have additional alerts (critical, emergency), but a sensor driver registered with thermal OF should disable any additional alerts. - Similarly, a sensor driver should disable alerts when there is no current trip temperature or hysteresis. (E.g., we're below the lowest trip point.) Implementation-wise: - The struct thermal_zone_of_device_ops needs an additional function to set the current sensor trip temperature and hysteresis. Presence of this function indicates the sensor driver has interrupt support. - The thermal OF device will call this function every time the temperature slides across trip points. (Or when trip points are altered.) - The thermal OF device should ignore the polling delay (set it to 0) if its sensor has interrupt support. (In this case, we can also make polling-delay optional. It's currently required in the device tree.) - On interrupt, the sensor driver should call thermal_zone_device_update with its thermal_zone_device, as returned by thermal_zone_of_sensor_register. My only concern is that I don't understand kernel contexts and interrupt handling well enough. It looks like at least its up to the sensor driver to ensure calls into the thermal subsystem have long left the hardware interrupt context, which I think should be sufficient. Hoping all of this sounds about right! -- Stéphan Kochen -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
