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

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Message-ID: <a5bc2227-5d25-41da-9b5b-ebc2d5fc85c8@suse.de>
Date: Tue, 30 Sep 2025 00:50:41 +0300
From: Stanimir Varbanov <svarbanov@...e.de>
To: Guenter Roeck <linux@...ck-us.net>, Stefan Wahren <wahrenst@....net>
Cc: Stanimir Varbanov <svarbanov@...e.de>, 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,

On 9/25/25 5:34 PM, Guenter Roeck wrote:
> On Thu, Sep 25, 2025 at 07:26:10AM +0200, Stefan Wahren wrote:
>> 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.

Thank you Stefan for the explanation.

>>
> Ok. Please make sure to add this explanation to the patch description.

Sure, I will extend the description in next version.

~Stan