From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Belloni Subject: Re: [PATCH 1/3] mfd: add Cypress FM33256B Processor Companion driver Date: Tue, 3 May 2016 10:14:18 +0200 Message-ID: <20160503081418.GC2335@piout.net> References: <1461150471-23163-1-git-send-email-jlp@gomspace.com> <1461150471-23163-2-git-send-email-jlp@gomspace.com> <20160422193232.GA9737@rob-hp-laptop> <20160422201153.GB17051@piout.net> <571F7BD2.60201@gomspace.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <571F7BD2.60201-jTq9jD7AHYRWk0Htik3J/w@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jeppe Ledet-Pedersen Cc: Rob Herring , lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, arnd-r2nGTMty4D4@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, a.zummo-BfzFCNDTiLLj+vYz1yj4TQ@public.gmane.org, pawel.moll-5wv7dgnIgG8@public.gmane.org, mark.rutland-5wv7dgnIgG8@public.gmane.org, ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org, galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org On 26/04/2016 at 16:31:46 +0200, Jeppe Ledet-Pedersen wrote : > > Good catch, I didn't look at this patch but it includes a lot of code > > that should be going to the RTC driver. > > If trickle charging is not enabled, I guess the RTC will not charge its > > backup battery. > > Thank you for the comments. > > Alexandre is correct. If the "cypress,charge-enabled" property is > present, the internal 80 uA trickle charger is enabled to charge a > backup capacitor on the VBAK pin. > > Do you want more code than the trickle charger setup moved to the RTC > driver? > I guess the 32k oscillator could go in the rtc driver too. > >>> +- cypress,charge-fast: enable fast (1 mA) charging > >> > >> What does fast mean? > >> > > Fast charging means charging with 1 mA instead of 80 uA. The wording is > from the datasheet, but I agree it should be renamed to something that > better explains what the difference is. > > >> I think it is time for a common binding here. There's all sorts of > >> variations on setting the charge current in bindings. Add something like > >> "charge-current-microamp" in power_supply.txt and use it here. Then > >> 1000uA implies "fast charge". > > > > Well, this is not a power supply, it is an RTC. > > > > I think both properties should got to the RTC subdevice and be parsed in > > the RTC driver. > > The backup capacitor is primarily used to supply current to the RTC, but > a couple of other registers are also battery-backed (watchdog reset > cause, event counter), so I put the charger setup in the main MFD file. > > If you prefer, I can move them both to the RTC driver? I would prefer unless you think that many people are not using the RTC while still using the watchdog (I'd say that is not the case). > > > Note that for trickle charging, we currently have the following > > properties: > > - trickle-resistor-ohms > > - trickle-diode-disable > > - abracon,tc-diode > > - abracon,tc-resistor > > > > abracon,tc-resistor can be replaced by trickle-resistor-ohms, I'll make > > a patch but abracon,tc-diode allows to select a diode type (and in > > particular a voltage drop). > > > > I think we could add a trickle-current-microamp like you suggested and > > trickle-diode-disable can be reused. > > So replace "cypress,charge-enabled/charge-fast" with > "trickle-current-microamp" and a check for 0/80/1000 uA? > Yeah, seems fine. -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html