[PATCH v2 2/2] arm64: dts: rockchip: Add rk3576 evb2 board

[Chaoyi Chen]

On 1/8/2026 4:11 PM, Alexey Charkov wrote:
> On Thu, Jan 8, 2026 at 12:02 PM Chaoyi Chen <kernel at airkyi.com> wrote:
>>
>> On 1/8/2026 3:42 PM, Chaoyi Chen wrote:
>>> Hello Alexey, Andrew,
>>>
>>> On 1/8/2026 2:53 PM, Alexey Charkov wrote:
>>>> On Wed, Jan 7, 2026 at 10:18 PM Andrew Lunn <andrew at lunn.ch> wrote:
>>>>>
>>>>>> +&gmac0 {
>>>>>> +     clock_in_out = "output";
>>>>>> +     phy-mode = "rgmii-rxid";
>>>>>
>>>>> rgmii-rxid is odd. Does the PCB really have an extra long TX clock
>>>>> line, but a short RX clock line?
>>>>>
>>>>> Try changing this to rgmii-id, and drop the tx_delay property.
>>>>
>>>> Actually it would be great if Rockchip could clarify the delay
>>>> duration introduced by a single delay element in GMAC-IOMUX delay
>>>> lines, which are controlled in the GMAC driver by the {tx,rx}_delay
>>>> properties. Maybe we could then switch to using
>>>> {tx,rx}_internal_delay_ps for fine-tuning the delays on the GMAC side
>>>> as envisaged in DT bindings [1], and use phy-mode = "rgmii-id"
>>>> throughout. Chaoyi, any chance you could ask around in your hardware
>>>> team?
>>>>
>>>> Currently though removing the delays at GMAC side altogether causes
>>>> unstable link operation - see [2] for example.
>>>>
>>>> [1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/net/ethernet-controller.yaml#L342-L347
>>>> [2] https://gitlab.collabora.com/hardware-enablement/rockchip-3588/linux/-/commit/372f3e9ae62cc62cdf2543391ea57be6bb548a0c
>>>
>>> Sorry, this problem has been discussed many times before. It's because
>>> the gmac on the Rockchip platform currently relies on setting the
>>> corresponding delay via phy-mode [3].
>>>
>>> [3] https://lore.kernel.org/all/mqoyjn7mnq6tmt6n6oev4wa3herjaxlupml2fmcampwiajvj4a@r5zs4d3jdm5p/
>>>
>>> The delay introduced by the delay line is not absolute. In reality,
>>> it depends on factors such as the chip's design and process technology.
>>>
>>> And for RK3576, you can assume that:
>>>
>>>       time(ns) = 0.0579 * delay_line_count + 0.105
>>>
>>> For example, tx_delay = <0x20> means:
>>>
>>>       time = 0.0579 * 0x20 + 0.105 ns = 1.9578 ns
>>>
>>> And I believe {tx,rx}_internal_delay_ps is indeed a good idea.
>>> I'll try to add them in v3. Thanks.
>>>
>>
>> I've also see some dt that use {tx,rx}_internal_delay_ps inside the PHY,
>> and compared to doing it in the MAC, which one is the better choice?
> 
> Your PHY defaults to 1950ps in rgmii-id [1], so adding anything on top
> of that on GMAC side would land you with a longer total TX delay than
> you currently get according to the coefficients you've just posted
> (1784.1ps). I would say go for "tx-internal-delay-ps = <1800>" on the
> PHY side for the closest match.
> 
> [1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/net/motorcomm%2Cyt8xxx.yaml#L36

Ah, I thought it was something like this:

&gmac0 {
	phy-mode = "rgmii";
	tx-internal-delay-ps = <1784>;
};

But what you actually said was this:

&mdio1 {
	rgmii_phy: ethernet-phy at 1 {
		compatible = "ethernet-phy-ieee802.3-c22";
		reg = <0x1>;
		tx-internal-delay-ps = <1784>;
	};
};

These two `tx-internal-delay-ps` things shouldn't be the same, right?

-- 
Best, 
Chaoyi