Re: [PATCH] board: rockchip: Add FriendlyElec NanoPi Zero2

[Quentin Schulz <quentin.schulz@cherry.de>]

Hi Jonas,

On 1/15/26 2:35 PM, Jonas Karlman wrote:
> Hi Quentin,
> 
> On 1/15/2026 1:24 PM, Quentin Schulz wrote:
>> Hi Jonas,
>>
>> On 1/10/26 9:53 PM, Jonas Karlman wrote:
>>> The NanoPi Zero2 is a small single board computer developed by
>>> FriendlyElec, based on the Rockchip RK3528A SoC.
>>>
>>> Add support for the FriendlyElec NanoPi Zero2 board.
>>>
>>> Features tested on a FriendlyElec NanoPi Zero2 2407:
>>> - SD-card boot
>>> - eMMC boot
>>> - Ethernet
>>> - USB host
>>>
>>> Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
>>> ---
>>>    arch/arm/dts/rk3528-nanopi-zero2-u-boot.dtsi | 11 ++++
>>>    arch/arm/mach-rockchip/rk3528/MAINTAINERS    |  6 ++
>>>    configs/nanopi-zero2-rk3528_defconfig        | 64 ++++++++++++++++++++
>>>    doc/board/rockchip/rockchip.rst              |  1 +
>>>    4 files changed, 82 insertions(+)
>>>    create mode 100644 arch/arm/dts/rk3528-nanopi-zero2-u-boot.dtsi
>>>    create mode 100644 configs/nanopi-zero2-rk3528_defconfig
>>>
>>> diff --git a/arch/arm/dts/rk3528-nanopi-zero2-u-boot.dtsi b/arch/arm/dts/rk3528-nanopi-zero2-u-boot.dtsi
>>> new file mode 100644
>>> index 000000000000..3e2fbd81da17
>>> --- /dev/null
>>> +++ b/arch/arm/dts/rk3528-nanopi-zero2-u-boot.dtsi
>>> @@ -0,0 +1,11 @@
>>> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>>> +
>>> +#include "rk3528-u-boot.dtsi"
>>> +
>>> +&vdd_arm {
>>> +	regulator-init-microvolt = <953000>;
>>> +};
>>> +
>>> +&vdd_logic {
>>> +	regulator-init-microvolt = <900000>;
>>> +};
>>
>> Why? We need an explanation here to know if and when we can get rid of
>> those additions. Why aren't those in the Linux kernel tree?
> 
> All prior regulator-init-microvolt props was purged from Linux DTs some
> time ago [1], instead of adding a dt-binding for this prop :/
> 
> After that change we now need to keep track of any initial microvolt
> that should be set by U-Boot in -u-boot.dtsi files.
> 
> If I remember correctly these regulators may have been initialized with
> too low or high voltage out of reset, and this ensure stable operation.
> 

That seems odd to me. Why could it reach U-Boot (where the regulator 
driver would then enable the regulator at voltage init-microvolt) if the 
regulator was initialized too low/high out of reset? Especially for 
vdd_arm, the CPU supply.

I'm not sure we'll be able to convince the DT binding people to add this 
property though, it all seems like a problem related to devfreq not 
being handled in U-Boot that could be resolved by configuring the 
clock-tree + regulator-tree properly appropriately I guess (which is 
easier said than done :) ).

We already have plenty of boards with that property (including some I 
maintain... news to me :) ), one more won't hurt us, so

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

Thanks,
Quentin