Date: Mon, 24 Jun 2024 19:55:31 +0200
From: Dragan Simic <dsimic@...jaro.org>
To: linux-rockchip@...ts.infradead.org
Cc: heiko@...ech.de, linux-arm-kernel@...ts.infradead.org,
 devicetree@...r.kernel.org, robh+dt@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux-kernel@...r.kernel.org, alchark@...il.com
Subject: Re: [PATCH] arm64: dts: rockchip: Delete the SoC variant dtsi for
 RK3399Pro

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@...jaro.org>
> ---
>  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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