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([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-720bbfc35b2sm12186289b3a.0.2024.11.06.10.19.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 Nov 2024 10:19:21 -0800 (PST) Sender: Guenter Roeck Message-ID: Date: Wed, 6 Nov 2024 10:19:19 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] dt-bindings: trivial-devices: add ltp8800 To: Conor Dooley Cc: Cedric Encarnacion , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, linux-doc@vger.kernel.org, linux-hwmon@vger.kernel.org, Jean Delvare , Jonathan Corbet , Delphine CC Chiu , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Peter Yin , Noah Wang , Marek Vasut , Lukas Wunner References: <20241106030918.24849-1-cedricjustine.encarnacion@analog.com> <20241106030918.24849-2-cedricjustine.encarnacion@analog.com> <8e4dc080-d779-4b06-8fd1-74784e06323a@roeck-us.net> <20241106-gatherer-glancing-495dbf9d86c7@spud> <20241106-overcast-yummy-9c6462ff2640@spud> <2b731ba8-1b6b-41eb-bae9-3403555506ef@roeck-us.net> <20241106-splurge-slaw-b4f1d33e4b09@spud> 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 CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 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 JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= In-Reply-To: <20241106-splurge-slaw-b4f1d33e4b09@spud> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/6/24 08:54, Conor Dooley wrote: > On Wed, Nov 06, 2024 at 08:43:54AM -0800, Guenter Roeck wrote: >> On 11/6/24 08:11, Conor Dooley wrote: >>> On Wed, Nov 06, 2024 at 04:06:02PM +0000, Conor Dooley wrote: >>>> On Tue, Nov 05, 2024 at 08:34:01PM -0800, Guenter Roeck wrote: >>>>> On 11/5/24 19:09, Cedric Encarnacion wrote: >>>>>> Add Analog Devices LTP8800-1A, LTP8800-2, and LTP8800-4A DC/DC μModule >>>>>> regulator. >>>> >>>> A single compatible for 3 devices is highly suspect. What is >>>> different between these devices? >>> >>> Additionally, looking at one of the datasheets, this has several inputs >>> that could be controlled by a GPIO, a clock input and several supply >>> inputs. It also has a regulator output. I don't think it is suitable for >>> trivial-devices.yaml. >>> >> >> All PMBus devices are by definition regulators with input and output voltages. >> After all, PMBus stands for "Power Management Bus". Some of them are listed >> in trivial devices, some are not. Is that a general guidance, or in other >> words should I (we) automatically reject patches adding PMBus devices >> to the trivial devices file ? > > Personally I like what Jonathan does for iio devices, where he requires > input supplies to be documented, which in turns means they can't go into > trivial-devices.yaml. I wanted to add an input supply option to > trivial-devices.yaml but ?Rob? was not a fan. I may be missing something, but doesn't every chip have an input supply ? granted, PMBus chips often have more than one, but still ... > In this case it would need a dedicated binding to document the regulator > child node and permit things like regulator-always-on or for any > consumers of the regulator to exist. I suppose that probably applies to > all pmbus bindings? Yes. There may be a few exceptions, for example if a fan controller is modeled as PMBus device, but that is rare. From a driver perspective, exposing regulator nodes is optional, though. > In this case, there seems to be an input "sync" clock that may need to > be enabled, which is another nail in the coffin for > trivial-devices.yaml. I really don't know if it is a good idea to expose such data. That clock can be connected to ground. It is only necessary in power-sharing configurations, and requires all chips to use the same clock. I'd assume it to be a fixed clock in pretty much all circumstances. The frequency needs to be configured into the chip, but that needs to be done during board manufacturing because it determines the switching frequency. Writing wrong data into the chip may render the board unusable or even destroy it (I destroyed several PMBus chips myself while playing with such parameters on evaluation boards). Maybe there is some use case where changing the configuration is necessary, but I am not in favor of exposing it due to the risk involved. Thanks, Guenter