Re: [PATCH] arm64: dts: rockchip: Delete the SoC variant dtsi for RK3399Pro

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Hello all,

Just checking, are there any comments on this patch?  Is there something
more I can do to have it accepted?


On 2024-06-02 08:25, Dragan Simic wrote:
The commit 587b4ee24fc7 ("arm64: dts: rockchip: add core dtsi file for
RK3399Pro SoCs") describes the RK3399Pro's PCI Express interface as the way built-in NPU communicates with the rest of the SoC. All available evidence shows this not to be accurate, as described in detail below. Moreover, the
rk3399pro.dtsi isn't used anywhere, so let's delete it.

The publicly available schematics of the Radxa Rock Pi N10 carrier board [1] and the Vamrs VMARC RK3399Pro SoM, [2] which put together form the currently single supported RK3399Pro-based board, clearly show that the PCI Express x4 interface of this SoC is fully functional and actually not used by the SoC to communicate with the built-in NPU. In more detail, the VMARC SoM exports the SoC's PCI Express interface at its board-to-board connector, and the Rock
Pi N10 routes it to an M.2 M-key slot with four PCI Express lanes.

Both the Rockchip RK3399Pro datasheet, version 1.1, [3] and the Rockchip RK3399Pro technical reference manual (TRM), first part of the version 1.0, [4] don't describe that the SoC's PCI Express interface is reserved for the NPU. Instead, the RK3399Pro TRM describes that the NPU uses AHB and AXI interfaces as the host interface (HIF). The RK3399Pro datasheet clearly describes that the PCI Express x4 interface is available for general-purpose use, just like it's the case with the standard Rockchip RK3399 SoC, [5] albeit with a bit
shorter feature list provided in the RK3399Pro datasheet.

Even the publicly available reference RK3399Pro schematic from Rockchip [6] shows the availability of a standard PCI Express slot with four lanes, which would be pretty much impossible if the PCI Express interface was reserved
for the communication with the built-in NPU.

Based on the RK3399Pro datasheet [3] and the board schematics, [2][6] the built-in NPU actually exports NPU_PCIE as a separate PCI Express x2 interface that's partially pinmuxed with the NPU's separate USB 3.0 interface, which is described further in the next paragraph. However, the NPU's separate PCI Express x2 interface is left undocumented in the publicly available RK3399Pro documentation, in which it's clearly described as reserved for internal use and not intended for the communication with the NPU. Finally, the evidently independent nature of the separate NPU_PCIE x2 interface makes ignoring it safe when it comes to determining the nature and the availability of the
RK3399Pro's main PCI Express x4 interface.

The actual application-level communication with the built-in NPU, including powering it up and down and uploading the NPU firmware, is performed through the separate USB 2.0 and USB 3.0 interfaces exported by the NPU, [7] which the VMARC SoM [2] and the reference board design from Rockchip [6] route to the SoC's standard USB 2.0 and USB 3.0 interfaces, to make the NPU accessible
to software running on the SoC's ARM cores.

[1] https://dl.radxa.com/rockpin10/docs/hw/rockpi_n10_sch_v1.1_20190909.pdf [2] https://dl.radxa.com/rockpin10/docs/hw/VMARC_RK3399Pro_sch_V1.1_20190619.pdf
[3] https://www.rockchip.fr/RK3399Pro%20datasheet%20V1.1.pdf
[4] https://www.rockchip.fr/Rockchip%20RK3399Pro%20TRM%20V1.0%20Part1.pdf
[5] https://www.rockchip.fr/RK3399%20datasheet%20V1.8.pdf
[6] https://opensource.rock-chips.com/images/e/e4/RK_EVB_RK3399PRO_LP3S178P332SD8_V11_20181113_RZF.pdf
[7] https://wiki.radxa.com/RockpiN10/dev/NPU-booting

Signed-off-by: Dragan Simic <dsimic@xxxxxxxxxxx>
---
 arch/arm64/boot/dts/rockchip/rk3399pro.dtsi | 22 ---------------------
 1 file changed, 22 deletions(-)
 delete mode 100644 arch/arm64/boot/dts/rockchip/rk3399pro.dtsi

diff --git a/arch/arm64/boot/dts/rockchip/rk3399pro.dtsi
b/arch/arm64/boot/dts/rockchip/rk3399pro.dtsi
deleted file mode 100644
index bb5ebf6608b9..000000000000
--- a/arch/arm64/boot/dts/rockchip/rk3399pro.dtsi
+++ /dev/null
@@ -1,22 +0,0 @@
-// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
-// Copyright (c) 2019 Fuzhou Rockchip Electronics Co., Ltd.
-
-#include "rk3399.dtsi"
-
-/ {
-	compatible = "rockchip,rk3399pro";
-};
-
-/* Default to enabled since AP talk to NPU part over pcie */
-&pcie_phy {
-	status = "okay";
-};
-
-/* Default to enabled since AP talk to NPU part over pcie */
-&pcie0 {
-	ep-gpios = <&gpio0 RK_PB4 GPIO_ACTIVE_HIGH>;
-	num-lanes = <4>;
-	pinctrl-names = "default";
-	pinctrl-0 = <&pcie_clkreqn_cpm>;
-	status = "okay";
-};

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