linux-kernel - Re: [PATCH v2] arm64: dts: rockchip: add attiny_rst

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Message-ID: <75946cd5-8f6f-40fd-a218-66d399a0da19@cherry.de>
Date: Fri, 27 Sep 2024 11:50:46 +0200
From: Quentin Schulz <quentin.schulz@...rry.de>
To: Heiko Stuebner <heiko@...ech.de>,
 Jakob Unterwurzacher <jakobunt@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
 Jakob Unterwurzacher <jakob.unterwurzacher@...rry.de>
Subject: Re: [PATCH v2] arm64: dts: rockchip: add attiny_rst_gate to Ringneck

Hi Heiko,

On 9/27/24 11:39 AM, Heiko Stuebner wrote:
> Am Donnerstag, 26. September 2024, 15:24:03 CEST schrieb Quentin Schulz:
>> Hi Jakob,
>>
>> On 9/26/24 3:20 PM, Jakob Unterwurzacher wrote:
>>> Ringneck v1.4 can contain (placement option) an on-board ATtiny
>>> microcontroller instead of an STM32. In normal operation, this
>>> is transparent to the software, as both microcontrollers emulate
>>> the same ICs (amc6821 and isl1208).
>>>
>>> For flashing the ATtiny, the SWITCH_REG1 regulator of the board's PMIC is
>>> used to enable the ATtiny UPDI debug interface. If the STM32 is placed, or if
>>> we are running on an older Ringneck revision, SWITCH_REG1 is not connected
>>> and has no effect.
>>>
>>> Add attiny-updi-gate-regulator so userspace can control it via sysfs
>>> (needs CONFIG_REGULATOR_USERSPACE_CONSUMER):
>>>
>>>     echo enabled > /sys/devices/platform/attiny-updi-gate-regulator/state
>>>
>>> Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@...rry.de>
>>> Tested-by: Quentin Schulz <quentin.schulz@...rry.de>
>>
>> Reviewed-by: Quentin Schulz <quentin.schulz@...rry.de>
>>
>> This is a candidate for backporting to stable branches as well I assume,
>> @Heiko?
> 
> That is more on the darker side of gray here.
> 
> Looking at the stable-kernel-rules [0] the criteria is
>    "It must either fix a real bug that bothers people or just add a device ID"
> 
> This change instead is adding a new feature to allow said flashing from a
> running system.
> 

This does mean that the new version of the device won't work as well 
with an older kernel though.

I thought the rules for DT backporting were a bit more permissive than 
for drivers. Maybe because most of the DT patches I posted were actual 
fixes :)

Up to you!

Cheers,
Quentin