linux-kernel - Re: [PATCH] mfd: intel_soc_pmic_chtdc_ti: Set use_single_read regmap

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Message-ID: <7e144b7f-8bc5-45f2-87af-acc1d7a70fb1@kernel.org>
Date: Mon, 4 Aug 2025 14:08:47 +0200
From: Hans de Goede <hansg@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Lee Jones <lee@...nel.org>, Andy Shevchenko <andy@...nel.org>,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] mfd: intel_soc_pmic_chtdc_ti: Set use_single_read
 regmap_config flag

Hi,

On 4-Aug-25 10:57 AM, Andy Shevchenko wrote:
> On Mon, Aug 4, 2025 at 10:51 AM Hans de Goede <hansg@...nel.org> wrote:
>> On 4-Aug-25 10:47 AM, Andy Shevchenko wrote:
>>> On Mon, Aug 4, 2025 at 10:34 AM Hans de Goede <hansg@...nel.org> wrote:
> 
> ...
> 
>>>> +       /* Reading multiple registers at once is not supported */
>>>> +       .use_single_read = true,
>>>
>>> By HW or by problem in regmap as being suggested here:
>>> https://lore.kernel.org/linux-gpio/CALNFmy1ZRqHz6_DD_2qamm-iLQ51AOFQH=ahCWRN7SAk3pfZ_A@mail.gmail.com/
>>> ?
>>
>> This is a hw limitation. I tried with i2ctransfer to directly
>> access the chip and it returns invalid values (1) after
>> the first byte read.
> 
>> 1) I don't remember if it was 0, 0xff or repeating
>> of the first byte. But it definitely did not work.
> 
> Perhaps elaborate the above in the comment, by at least putting
> keyword HW there?

Ok, I've just send out a v2 clarifying the comment.

Regards,

Hans