Re: [RFC PATCH 2/2] PCI: rockchip-host: drop wait on PERST# toggle

Dragan Simic
2025-11-10T00:01:50Z

Hello Geraldo,

On Wednesday, November 05, 2025 04:55 CET, Geraldo Nascimento <geraldogabriel@gmail.com> wrote:
> I did some more testing, intrigued by why would a delay of more than
> 5 ms after the enablement of the power rails trigger failure in
> initial link-training.
>
> Something in my intuition kept telling me this was PERST# related,
> and so I followed that rabbit-hole.
>
> It seems the following change will allow the SSD to work with the
> Rockchip-IP PCIe core without any other changes. So it is purely
> a DT change and we are able to keep the mandatory 100ms delay
> after driving PERST# low, as well as the always-on/boot-on
> properties of the 3v3 power regulator.
>
> This time everything is within the PCIe spec AFAICT, PERST# indeed
> is an Open Drain signal, and indeed it does requires pull-up resistor
> to maintain the drive after driving it high.
>
> I'm still testing the overall stability of this, let's hope for the
> best!
>
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399pro-vmarc-som.dtsi b/arch/arm64/boot/dts/rockchip/rk3399pro-vmarc-som.dtsi
> index aa70776e898a..1c5afc0413bc 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399pro-vmarc-som.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399pro-vmarc-som.dtsi
> @@ -383,13 +383,14 @@ &pcie_phy {
> };
>
> &pcie0 {
> - ep-gpios = <&gpio0 RK_PB4 GPIO_ACTIVE_HIGH>;
> + ep-gpios = <&gpio0 RK_PB4 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
> num-lanes = <4>;
> - pinctrl-0 = <&pcie_clkreqnb_cpm>;
> + pinctrl-0 = <&pcie_clkreqnb_cpm>, <&pcie_perst>;
> pinctrl-names = "default";
> vpcie0v9-supply = <&vcca_0v9>; /* VCC_0V9_S0 */
> vpcie1v8-supply = <&vcca_1v8>; /* VCC_1V8_S0 */
> vpcie3v3-supply = <&vcc3v3_pcie>;
> + max-link-speed = <2>;

FWIW, we shouldn't be enabling PCIe Gen2 here, because it's been
already disabled for the RK3399 due to unknown errata in the commit
712fa1777207 ("arm64: dts: rockchip: add max-link-speed for rk3399",
2016-12-16). It's perfectly reasonable to assume the same for the
RK3399Pro, which is basically RK3399 packaged together with RK1808,
AFAIK with no on-package interconnects.

> status = "okay";
> };
>
> @@ -408,6 +409,10 @@ pcie {
> pcie_pwr: pcie-pwr {
> rockchip,pins = <4 RK_PD4 RK_FUNC_GPIO &pcfg_pull_up>;
> };
> + pcie_perst: pcie-perst {
> + rockchip,pins = <0 RK_PB4 RK_FUNC_GPIO &pcfg_pull_up>;
> + };
> +
> };
>
> pmic {