From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.andi.de1.cc (mail.andi.de1.cc [178.238.236.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57AC62038D7; Tue, 29 Oct 2024 08:44:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.238.236.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730191447; cv=none; b=ARhyIItv5+COxupa9GQ2HviwcIHCpQcbre/WgjwkK4x8vNmOqYZOhnZdvOKvVN+k3gpp3oL2blPKevfeCQJH8Zwivj5jVJ6bF88HJ/fVsaQ7rI18p0uQzp25/obtx0CUjxVvAOn8eYnPSd7LHk/C3j7FHryepR0qyzBx/3rYzhc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730191447; c=relaxed/simple; bh=29GtuOb78Tq1qYNR/nE/cnVHgRQpd26VnE8XbAtvsAY=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=p1V5IJ7apsJTC4CG/VxMRWdnRu5y5O3AhYkBRPMN4jdkH/x9Ca6dDCjsOksYr5Rg+vREwrmfe5eedCsthvIsIkuUwreQvrORb6l4nG4gnrcwCzxH2Jzyzn7HYJZ2QitnCnj2EhHLAT7lyZ5KWMsxMgDsVEmYjbt/d7LKzNZbk24= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=kemnade.info; spf=pass smtp.mailfrom=kemnade.info; dkim=pass (2048-bit key) header.d=kemnade.info header.i=@kemnade.info header.b=C8PH7V93; arc=none smtp.client-ip=178.238.236.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=kemnade.info Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kemnade.info Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kemnade.info header.i=@kemnade.info header.b="C8PH7V93" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kemnade.info; s=20220719; h=References:In-Reply-To:Cc:From:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID; bh=q9tbeX7y+zJgZuAb/cGAaZ6MuCs4CQFq8FQvgssvj5E=; b=C8PH7V936k7jSRlqWNh/9IP9kq 2lMBc9oVA6BILyiZI4TvY/qs23GQNfOWpQipGokmPTcvgTR+8AsdYx/mQol5PQ4B9Q3BXKcA5vwL0 qaWWQBolR7aLKV1lPlDpe5qo7inNYIGy9fBvYgJYW28sCoV0QHkz/H9sBYaDd6geVj06rE866fs0k 9UGEXv8I8JgXoDP8Bf/Zrom5MoisZ/iRJSIfZoFwauhEu2WhjwMcdPpDRhJu/D0pWBQAcH+Kqw8RX 8FaYwoKRFjv4uv4cIaJd4NoZ2rZD6+W6BKaJdpB5qf6LUGoYxilHQ2YT+yj+/Ga7ZYy4IJ77fJWEx lRU3k4KQ==; Date: Tue, 29 Oct 2024 09:44:02 +0100 From: Andreas Kemnade To: Matti Vaittinen Cc: Conor Dooley , Shawn Guo , linux-kernel@vger.kernel.org, Fabio Estevam , devicetree@vger.kernel.org, Pengutronix Kernel Team , Rob Herring , Krzysztof Kozlowski , linux-arm-kernel@lists.infradead.org, Sascha Hauer , Alexander Stein , imx@lists.linux.dev, sre@kernel.org Subject: Re: [PATCH v2 2/3] ARM: dts: imx: Add devicetree for Kobo Clara 2E Message-ID: <20241029094402.382594c5@akair> In-Reply-To: References: <20241024142206.411336-1-andreas@kemnade.info> <20241024142206.411336-3-andreas@kemnade.info> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Am Tue, 29 Oct 2024 09:53:33 +0200 schrieb Matti Vaittinen : > On 24/10/2024 17:22, Andreas Kemnade wrote: > > Adds a devicetree for the Kobo Clara 2E Ebook reader. It is based > > on boards marked with "37NB-E60K2M+4A2" or "37NB-E60K2M+4B0". It is > > equipped with an i.MX6SLL SoC. > > > > Expected to work: > > - Buttons > > - Wifi > > - Bluetooth > > (if Wifi is initialized first, driver does not handle > > regulators yet) > > - LED > > - uSD > > - USB > > - RTC > > - Touchscreen > > > > Add human-readable comments for devices without mainlined driver and > > binding. Such comments can e.g. be help to find testers if someone > > starts to work on the missing drivers. > > > > Signed-off-by: Andreas Kemnade > > ... > > > + > > + pmic@4b { > > + compatible = "rohm,bd71879", "rohm,bd71828"; > > + reg = <0x4b>; > > + pinctrl-names = "default"; > > + pinctrl-0 = <&pinctrl_bd71828>; > > + > > + interrupt-parent = <&gpio4>; > > + interrupts = <19 IRQ_TYPE_LEVEL_LOW>; > > + system-power-controller; > > + > > + clocks = <&clks 0>; > > + #clock-cells = <0>; > > + clock-output-names = "bd71828-32k-out"; > > + > > + gpio-controller; > > + #gpio-cells = <2>; > > + gpio-reserved-ranges = <0 1>, <2 1>; > > + > > + rohm,charger-sense-resistor-ohms = <30000000>; > > I am afraid that this one is _my_ very much terrible brainfart. Yeah, > pile up the stones and start casting ;) > ... at everyone who had looked at this and did not question it ;-) > I am fairly sure the sense resistor is 30 mOhm (0,030 Ohm), not 30 > MOhm (30 000 000 Ohm). (And I am the one who misinterpreted the M in > some email/data-sheet in the past - and never questioned the sanity). > Well, I did question it, but then thought, ok there might be some current mirror to scale things down so that the massive rsense might make sense. Well, no schematics here. > In short, AFAICS the sense resistor is added "in series" to the > system load. Eg: > > -------- > ---| Rsense |----- > | -------- | > --------- ------- > | VSupply | | Rload | > --------- ------- > | | > ------------------ > > Hence, by measuring the voltage drop on the Rsense gives us the > current flowing through the system ( good old U = RI ). > Yes, that is the way I did know how these things are usually done. So I am still on track. > I believe having 30 Mohm (30 000 000 Ohm) resistor there would not > make much of sense... With a Fermi estimate that the system works > with voltage magnitude of 1V and current magnitude of 1A and then > applying good old P = UI and U = RI would give us wonderful results > :) Quite a battery on poor Kobo, right? You'd better to not touch the > battery termninals ;) Oh, and looking the driver code I've written > for handling this property... Sometimes I really don't like mirrors :) > > Well, now that I got this out - I suppose this could be > rohm,charger-sense-resistor-milli-ohms = <30>; > or > rohm,charger-sense-resistor-micro-ohms = <30000>; > > I further guess there is no upstreamn binding doc for this property. The binding doc is upstream. So an impressive amount of maintainers had a look at it... Well, everyone seem to entrust Rohm Semiconductors to do magic... wonderful reputation. So how to proceed? As this property is not required, I can simply remove it and add a comment. > I think there is also no upstream charger driver for the > BD71828/BD71879 - only an early RFC and some downstream mess - but > stil it'd be nice to have the property in place as the size of the > sense resistor is needed when converting coulomb counter register > values to current. > What are you upstreaming plans here? For all: I rebased the charger stuff to v6.11 on https://github.com/akemnade/linux branch kobo/power-6.11 Regards, Andreas