linux-kernel - Re: [PATCH v4 4/5] iio: adc: ti-adc128s052: Add lower resolution devices support

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Message-ID: <bd72b92e-bf8d-4fc2-84ae-4f9fd8b40c37@baylibre.com>
Date: Sat, 28 Jun 2025 18:30:28 -0500
From: David Lechner <dlechner@...libre.com>
To: Sukrut Bellary <sbellary@...libre.com>,
 Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Matti Vaittinen <mazziesaccount@...il.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>,
 Angelo Compagnucci <angelo.compagnucci@...il.com>, Nishanth Menon
 <nm@...com>, linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/5] iio: adc: ti-adc128s052: Add lower resolution
 devices support

On 6/28/25 6:09 PM, Sukrut Bellary wrote:
> On Sat, Jun 14, 2025 at 09:45:43PM +0300, Andy Shevchenko wrote:
>> On Sat, Jun 14, 2025 at 12:15 PM Sukrut Bellary <sbellary@...libre.com> wrote:
>>>
>>> The adcxx communicates with a host processor via an SPI/Microwire Bus
>>> interface. The device family responds with 12-bit data, of which the LSB bits
>>> are transmitted by the lower resolution devices as 0.
>>> The unavailable bits are 0 in LSB.
>>> Shift is calculated per resolution and used in scaling and raw data read.
>>>
>>> Lets reuse the driver to support the family of devices with name
>>> ADC<bb><c>S<sss>, where
>>
>> I believe it's incorrect, i.e. it's something like ...S<ss><?>, where
>> <?> is something you need to clarify, and <ss> is definitely a speed
>> in kSPS.
>>
> Thank you for the review.
> I am not sure about the last s in <sss>.
> It could be TI's silicon spins versioning.
> I couldn't find any information about it in any of the datasheets.
> I can drop the last s or mark it as <ssx> and specify the first two <ss> as
> maximum speed.
> 
I have a hunch that the last digit has to do with pinout/number of
power supplies. adc128s052 has two supplies V_A and V_D while the
others only have V_A.

If this sounds vaguely familiar, it is because it was discussed
today in this thread [1] that Jonathan CC'ed you in. :-)

[1]: https://lore.kernel.org/linux-iio/20250628162910.1256b220@jic23-huawei/