From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f169.google.com (mail-pf1-f169.google.com [209.85.210.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 45BFD314A9D for ; Mon, 27 Oct 2025 16:52:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761583980; cv=none; b=g07OMDLnxpfFw7z6DbY7bv1DxPvyEZD2KByGZ8oeepM5+LOp3lDZ5Y78Ai6SkNfZ81ji/0K3yBsNLcEDXd9ZsXrdRothkcByrfYZLatT63lvCEpmd1LvCD7J9OrQ8m9fvKDIXRdIu33IT8rp3EyjbtHbhaffkNRh/R7L5kpcK1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761583980; c=relaxed/simple; bh=ez/mIQCI0gAsepx7KDmrGjw1VRoEx13dA304T/Eyp0g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=a1ruiNJSzyrobr8oS9dFzj5yPxG/Os4W7vkykmg461WBccjSD9u96unx1JVtTwALiiOw7vtZYqDkcCNZxJKTZHTr/oEM1tCkFR+I0Z6rSTUjFCLsX2Bmu07ZdugLL1aie5YInJGYVc2lTNdYsDfJBMQgWV9johfa627NQK+fJeM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jVi8eGW5; arc=none smtp.client-ip=209.85.210.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jVi8eGW5" Received: by mail-pf1-f169.google.com with SMTP id d2e1a72fcca58-76e2ea933b7so4742520b3a.1 for ; Mon, 27 Oct 2025 09:52:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1761583977; x=1762188777; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:sender:from:to:cc:subject:date:message-id:reply-to; bh=1UjUmi5Ka+7gfU5ZG8hAL+hkQbUFpTtINYP7f5ILrSk=; b=jVi8eGW55EGjyrRsXjvBSfyxC/oQYt7Yj6/g+YsyXkn3KA32KIQlrFnNVarbEqBI3s Yx4qQf/bkbAXK1z4QPBiwV8UDOPdwPfsjbIsJZh9egQXn2X5XjhK5foAUzLDDKEtJ5p8 IJrLrRQSfJTHWIJPhsWxyFj4A3/EiX0qhpiQBSb+qVO+X/63EumKBAWNheMKLiPULTIt Z9ADbTY4erHT9TGVeiCK4AU+JEK4dRfILsZclYxw7qVDAR6SYcH2s3lK+DjY1MsLmGYC neojcLp6c8ZFgJGOBZmoSsBTevZNq1b7YZ9uEDiW+/zN0VRFK++ccqShGPeAbSWkshYk WqMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761583977; x=1762188777; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:sender:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=1UjUmi5Ka+7gfU5ZG8hAL+hkQbUFpTtINYP7f5ILrSk=; b=gtQbqAVOpx7yIpKAt7FBA3pOF+Z+oLiw+NfZ8N3bIx5iGulIMMZ2IMZwmk1PJHiRNP Wjlf9N2pwyJB+gXPBcVF9BRK86q1d5RACHzXIpDs6A7lAvlLNYMYO245H6bPKbb6L8id jT+iYpC5PP4tqpom3xcz6CdLTPdHOiJZYOlomqMAcmvQuEsAkE4hFZ5KAvJiSuxBEg5c /8qKBEF8LmPnhl0/3bpYfYfolE/p31MoYWVABn1Wuryxzwshtj9C8HcGPLHlylUpxaMr lWl4PcBtKtPHmdo243Xt1VQQJ9D37aEdRMvv+w1s06g0u/E11FnW7VNDZd5OQ9ejMOW4 lN9A== X-Forwarded-Encrypted: i=1; AJvYcCWZVQzq1KvStNLz5huzuUAlIM+2d03KzzQ2UC9Io8LNLEVPZ6LYOFaRCwLh6Ea3teG2+thb7S/PqB8peQ==@vger.kernel.org X-Gm-Message-State: AOJu0YzJb6pZ/zWtd7Hy5aUtZffqIHVLVh0HR7ryCrSfsYSTkHnMGJRC DBFIBRydZvwEl0YYFmag0/fi4Q2DJrApJ6l7GXzB9SvGWSmS47qGytbbesaCow== X-Gm-Gg: ASbGncvd1v1RM/7ewMqwUJmHWYgahUuHD/EXITwB+sTFI8pbQ7xwunFLRllpbG5O5LW etkciMe2pDss5XjuAgZ6CNv1TcU1IbNcWosAN0GKdIXfp1ZYATayHtc+VBeZdraLhslXlJw04Le 3aH1aVkP5MCahdXjYbtLyXTdsJbUs2nkYXuE19TUZ35d5ekZ76PgdBPOCwAVXgF2b1tn33ca0ez MtOO2qMIYC/xIZJML1X9jrp9sqMiI2z5UeYaNTIuKYtCB/LholI6YCjxRglUOcjL3f7DEWYgzGL i099wFYKh9P2DyB3yxy/ZQ9cpeu6YwjlooDJj4GyYfbMRDEkMgI1qpYBHqyCY3TPzdy/+tF5YBE XHqgt+b3WXP85biNtyoKeLQ6wtjnu4NV6bMM3O5NoWYMpVWrYuZ4YeVRWp5/ecBK4Ag3RnG5UjM Go/Q5weXUtGRqV+PhZfeDteNc1x9I+k/YqfXSMu2Dhzm4YnG8tUMPc3eEN+20= X-Google-Smtp-Source: AGHT+IFq+QgzAYa0Pzepb131iFTCn1+g6011G4/2bAwqtv01tirsdxRlxBcZ2qwcf9EHIL7uZdLTBg== X-Received: by 2002:a05:6a20:430b:b0:246:3a6:3e47 with SMTP id adf61e73a8af0-344de5ddc8cmr202153637.12.1761583977229; Mon, 27 Oct 2025 09:52:57 -0700 (PDT) Received: from ?IPV6:2600:1700:e321:62f0:da43:aeff:fecc:bfd5? ([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7a414012bcesm8972989b3a.8.2025.10.27.09.52.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Oct 2025 09:52:56 -0700 (PDT) Sender: Guenter Roeck Message-ID: Date: Mon, 27 Oct 2025 09:52:53 -0700 Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] hwmon: Add TSC1641 I2C power monitor driver To: Igor Reznichenko Cc: conor+dt@kernel.org, corbet@lwn.net, david.hunter.linux@gmail.com, devicetree@vger.kernel.org, krzk+dt@kernel.org, linux-doc@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, robh@kernel.org, skhan@linuxfoundation.org References: <20251027064127.648712-1-igor@reznichenko.net> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: <20251027064127.648712-1-igor@reznichenko.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/26/25 23:41, Igor Reznichenko wrote: >> In some way this is inconsistent: It accepts a shunt resistor value of, say, 105 >> even though the chip can only accept multiples of 10 uOhm. In situations like this >> I suggest to expect devicetree values to be accurate and to clamp values entered >> through sysfs. More on that below. >> >>> + return 0; >>> +} >>> + >>> +static int tsc1641_set_shunt(struct tsc1641_data *data, u32 val) >>> +{ >>> + struct regmap *regmap = data->regmap; >>> + long rshunt_reg; >>> + >>> + if (tsc1641_validate_shunt(val) < 0) >>> + return -EINVAL; >>> + >>> + data->rshunt_uohm = val; >>> + data->current_lsb_ua = DIV_ROUND_CLOSEST(TSC1641_VSHUNT_LSB_NVOLT * 1000, >>> + data->rshunt_uohm); >>> + /* RSHUNT register LSB is 10uOhm so need to divide further*/ >>> + rshunt_reg = DIV_ROUND_CLOSEST(data->rshunt_uohm, TSC1641_RSHUNT_LSB_UOHM); >> >> This means that all calculations do not use the actual shunt resistor values used >> by the chip, but an approximation. I would suggest to store and use the actual shunt >> resistor value instead, not the one entered by the user. > > By "actual shunt" you mean defined in devicetree? Then does it mean disabling > writing value by user via sysfs and making "shunt_resistor" read-only or leaving it > writable and clamping to devicetree value, thus discarding the user provided value? > I said "used by the chip", and referred to the value written into TSC1641_RSHUNT_LSB_UOHM. >> See below - clamping is insufficient for negative values, and it is not clear to me if >> the limit register is signed or unsigned. > >> Also, the datasheet doesn't say that the limit value would be signed. Did you verify >> that negative temperature limit values are actually treated as negative values ? > > SUL, SOL, TOL are signed, I verified. The negative limits for current and temperature > work well based on my testing. > Please add a respective comment into the code. >> This doesn't work as intended for negative values. regmap doesn't expect to see >> negative register values and returns an error if trying to write one, so clamping >> against SHRT_MIN and SHRT_MAX is insufficient. You also need to mask the result >> against 0xffff. > > I was under impression regmap would handle this masking correctly when defining > .val_bits = 16. E.g. in regmap.c:973 it selects formatting function for 16bit values. > I can mask explicitly if it's required. > It certainly doesn't throw error since negative alerts work as mentioned. > My unit test code bails out on negative values, returning an error from regmap when trying to write negative values. I had seen that before. Masking the value passed to regmap with 0xffff solved the problem. >> Why did you choose lcrit/crit attributes instead of min/max ? If there is only >> one alert limit, that usually means the first level of alert, not a critical level. >> Raising an alert does not mean it is a critical alert. Please reconsider. > > I used hwmon/ina2xx.c as a reference. It covers many similar power monitors which > have single threshold alerts and defines only lcrit/crit. If this is a wrong approach > I'll change to min/max. Isn't that great ? You can always find an example for everything in the Linux kernel if you are looking for it. Guenter