linux-kernel - Re: [PATCH 2/4] hwmon: adc: rp1: Add Raspberry Pi's RP1 ADC driver

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Message-ID: <e53865df-7566-4790-9214-0af875950742@gmx.net>
Date: Thu, 25 Sep 2025 07:26:10 +0200
From: Stefan Wahren <wahrenst@....net>
To: Guenter Roeck <linux@...ck-us.net>, Stanimir Varbanov <svarbanov@...e.de>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rpi-kernel@...ts.infradead.org,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, linux-hwmon@...r.kernel.org,
 Jean Delvare <jdelvare@...e.com>, Rob Herring <robh@...nel.org>,
 Florian Fainelli <florian.fainelli@...adcom.com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
 Saenz Julienne <nsaenz@...nel.org>,
 Andrea della Porta <andrea.porta@...e.com>,
 Phil Elwell <phil@...pberrypi.com>, Jonathan Bell
 <jonathan@...pberrypi.com>, Dave Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH 2/4] hwmon: adc: rp1: Add Raspberry Pi's RP1 ADC driver

Hi Guenter,

Am 25.09.25 um 04:42 schrieb Guenter Roeck:
> On Thu, Sep 25, 2025 at 03:04:14AM +0300, Stanimir Varbanov wrote:
>> A five-input successive-approximation analogue-to-digital converter
>> with 12-bit (effective number of 9.5 bits) resolution at 500kSPS.
>> The ADC has four external inputs and one internal temperature sensor.
>>
>> Signed-off-by: Phil Elwell <phil@...pberrypi.com>
>> Signed-off-by: Jonathan Bell <jonathan@...pberrypi.com>
>> Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> I just realized that there is already a hwmon driver for
> Rasperri Pi - drivers/hwmon/raspberrypi-hwmon.c.
>
> Please add this code to that driver.
could you please explain the reason for this?

Yes, both drivers are for Raspberry Pi boards, but they don't share any 
code base. The raspberrypi-hwmon uses a mailbox interfaces to get the 
sensor data and works for the board generation 1 - 4. This driver works 
completely differently ( MMIO ), doesn't depend on the mailbox interface 
and applies only for board generation 5. Actually I don't see a benefit 
of merging them.

Best regards
>
>> ---
>>   drivers/hwmon/Kconfig   |  10 ++
>>   drivers/hwmon/Makefile  |   1 +
>>   drivers/hwmon/rp1-adc.c | 301 ++++++++++++++++++++++++++++++++++++++++
> Also, this needs documentation.
>
> Thanks,
> Guenter