From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C56F0D5B164 for ; Tue, 29 Oct 2024 08:54:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=q9tbeX7y+zJgZuAb/cGAaZ6MuCs4CQFq8FQvgssvj5E=; b=fSPnBZ/P6L3Me//xX+TF2ZCstT huunzQ0dKfYJLeknkspsVHex1BmyHWAS0lLnADgFXhjIkOZtf+WhD+7PCH+9vENNhH7+mEYtGgsVJ ILF/ItQVVayx85EAAxMF6G9hKRWWwyLBJaXatOkPzAqwjgCghH050B6M01eA3neIym6uWPWfj2btJ V5m9yE2IF+7T0CCX+H63dUdyidBX/7IBbLM5s0vARfck7e6S9FTDDbI3StiTalmU8ioF8iAOsH65h pZk4RMKdKIl1wBIB0okJwayYGwUoSiU82piDQYyLR3VOL0g/8o4w/7nM49/+JlAbM5T7LARBbSb9U 1KPhOgpQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t5hzj-0000000DlwQ-3z37; Tue, 29 Oct 2024 08:54:31 +0000 Received: from mail.andi.de1.cc ([2a02:c205:3004:2154::1]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t5hnQ-0000000DiT9-2jd8 for linux-arm-kernel@lists.infradead.org; Tue, 29 Oct 2024 08:41:52 +0000 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 09:41:41 +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: <20241029094141.04540d91@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) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241029_014148_735453_6B01C2E0 X-CRM114-Status: GOOD ( 32.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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