linux-kernel - Re: [PATCH v3 3/5] iio: amplifiers: ada4250: use devm_regulator_get_enable_read

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Message-ID: <fcd1af23-7d8b-4a0f-bae1-5a60f8876269@baylibre.com>
Date: Thu, 12 Jun 2025 10:31:04 -0500
From: David Lechner <dlechner@...libre.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] iio: amplifiers: ada4250: use
 devm_regulator_get_enable_read_voltage()

On 6/12/25 8:03 AM, Andy Shevchenko wrote:
> On Wed, Jun 11, 2025 at 04:33:03PM -0500, David Lechner wrote:
>> Use devm_regulator_get_enable_read_voltage() to simplify the code.
>>
>> Replace 1000000 with MICRO while we are touching this for better
>> readability.
> 
> ...
> 
>> -	voltage_v = DIV_ROUND_CLOSEST(voltage_v, 1000000);
>> +	voltage_v = DIV_ROUND_CLOSEST(st->avdd_uv, MICRO);
> 
> Side note. I'm always worry about CLOSEST choice when it's related to voltage
> or current. Imagine the table which gives you 5, 3.3, and 1.2. If it happens to
> be closest to higher value, it may damage HW forever.
> 

The rounding to volts seems strange to me too, but I could not find a public
datasheet for this part, so I wasn't able to determine what the "right" thing
to do is. It sounds like this is just some sort of small gain/offset calibration,
so I don't think there is any serious problem here, like it could damage the part.
So I will have to leave it to someone with the part and the datasheet to figure
out if there is actually a problem here.