Hi Pavel, Am 31.03.2015 um 09:26 schrieb Pavel Machek <pavel@xxxxxx>: > Hi! > >>>>> + io-channels = <&twl_madc 1>, >>>>> + <&twl_madc 10>, >>>>> + <&twl_madc 12>; >>>>> + io-channel-names = "temp", >>>>> + "ichg", >>>>> + "vbat"; >>>>> + }; >>>> >>>> Rather than just making platform_data into device tree properties.. >>>> >>>> Can't you hide the these custom properties behind the compatible flag? >>>> >>>> You can initialize that data in the driver based on the compatible >>>> flag and the match data. >>>> >>>> This makes sense if you can group things to similar configurations. >>> >>> Maybe I have not completely understood your proposal. >>> >>> Do you mean to go back to have big parameter tables for each device/battery >>> combination in the driver code and the compatible flag (e.g. compatible = “board17”) >>> chooses the right data set for the charging map and channels? >> >> If you can somehow group them, then yes. Not for every board if there >> are many of them naturally. >> >>> I thought this is what the DT was introduced for - to have the same driver >>> code but adapt to different boards depending on hardware variations. >> >> Yeah but you also need to consider the issues related to introducing >> new device tree properties. The device tree properties introduced >> should be generic where possible. >> >>> And batteries have very different characteristics and vary between devices… >> >> Right. Maybe that has been already agreed on to use capacity-uah for >> batteries in general? In that case I have not problem with that as >> it's a generic property :) >> >>> The charging maps are depending on the battery type connected to the twl4030 >>> and which madc channel is which value is also a little hardware dependent >>> (although the twl4030 doesn’t give much choice). >> >> Just to consider alternatives before introducing driver specific >> property for the maps.. Maybe here you could have few different type >> of maps and select something safe by default? Of course it could be this >> is higly board specific, I think some devices may be able to run below >> 3.3V for example.. > > As I explained in some other mail, those tables should not be > neccessary at all. They can be computed from li-ion characteristics > and internal resistance, and assumed current during charge and > discharge. I already explained that we do not know the charging and discharging current well enough for such a calculation. And I explained that the “internal resistance” is a system (battery + cables + connectors + other circuits) parameter that is not easy to derive or measure and type into the .dts source code. At least I have no idea how I should find it out for my boards. While I can easily determine the curves (and we already have them for the platform_data driver). Please propose your own code doing that so that we can test if it is better. > > Running below 3.3V.. not really. At that point, the battery is really > _empty_, and voltage is going down really really fast. It is the diffference between 2% and 0% where a fuel indication might be most important… > > Plus, you are damaging the battery at that point. The power controller will shut down - but the driver should report reasonable (but IMHO not necessarily perfect) values until the last moment. BR, Nikolaus -- 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
