linux-kernel - Re: [PATCH v2 6/7] iio: adc: ad485x: add ad485x driver

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Message-ID: <807d35e5-f479-4c1c-9761-b9dbb086fabc@baylibre.com>
Date: Fri, 11 Oct 2024 08:47:47 -0500
From: David Lechner <dlechner@...libre.com>
To: "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>,
 Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen
 <lars@...afoo.de>, "Hennerich, Michael" <Michael.Hennerich@...log.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, "Sa, Nuno" <Nuno.Sa@...log.com>,
 Olivier Moysan <olivier.moysan@...s.st.com>,
 Uwe Kleine-König <ukleinek@...nel.org>,
 Andy Shevchenko <andy@...nel.org>,
 "Schmitt, Marcelo" <Marcelo.Schmitt@...log.com>,
 Mike Looijmans <mike.looijmans@...ic.nl>,
 Marius Cristea <marius.cristea@...rochip.com>,
 Dumitru Ceclan <mitrutzceclan@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Alisa-Dariana Roman <alisadariana@...il.com>,
 Ivan Mikhaylov <fr0st61te@...il.com>,
 "Cuciurean, Sergiu" <Sergiu.Cuciurean@...log.com>,
 "Bogdan, Dragos" <Dragos.Bogdan@...log.com>,
 "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v2 6/7] iio: adc: ad485x: add ad485x driver

On 10/11/24 6:27 AM, Miclaus, Antoniu wrote:
>> On 10/8/24 5:48 AM, Miclaus, Antoniu wrote:
>>>>> +static int ad485x_get_calibscale(struct ad485x_state *st, int ch, int *val,
>> int
>>>> *val2)
>>>>> +{
>>>>> +       unsigned int reg_val;
>>>>> +       int gain;
>>>>
>>>> Should be u8 gain[2] and...
>>>
>>> As discussed in previous patch series, the bulk operations won't work for
>> these
>>> chips. The CS needs to be raised between each byte read/written.
>>>
>>
>> So the datasheet is wrong and Streaming Instruction Mode doesn't actually
>> work?
>>
>> There is also Nonstreaming Instruction Mode if we need to read/write
>> nonconsecutive
>> registers without deasserting CS.
> 
> The chip was set to Nonstreaming Instruction Mode from the start in the ad485x_setup() function.
> 
> And the datasheet specifies (page 49 of 70):
> "In nonstreaming instruction mode, one or more SPI transactions can be provided in
> a single SPI frame."
> 
> So I guess it is an error in the datasheet.

So maybe regmap bulk operations would work if we change it to
Streaming Instruction Mode (along with the correct increment
direction)?