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

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Message-ID: <592e9a1e-a58f-435d-aff7-13c13fe0598a@kernel.org>
Date: Mon, 4 Aug 2025 10:51:42 +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 Andy,

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:
>>
>> Testing has shown that reading multiple registers at once (for 10 bit
>> adc values) does not work. Set the use_single_read regmap_config flag
>> to make regmap split these for is.
>>
>> This should fix temperature opregion accesses done by
>> drivers/acpi/pmic/intel_pmic_chtdc_ti.c and is also necessary for
>> the upcoming drivers for the ADC and battery MFD cells.
> 
> ...
> 
>> +       /* 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.

> As a quick fix I am fine with this.
> Reviewed-by: Andy Shevchenko <andy@...nel.org>

Thank you.

Regards,

Hans


1) I don't remember if it was 0, 0xff or repeating
of the first byte. But it definitely did not work.