linux-kernel - Re: [PATCH v7 4/4] arm64: dts: ti: hummingboard-t: add overlays for m.2 pci-e and usb-3

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Message-ID: <299b6b75-beef-46aa-9203-b96009226677@solid-run.com>
Date: Mon, 28 Oct 2024 17:19:53 +0000
From: Josua Mayer <josua@...id-run.com>
To: Vignesh Raghavendra <vigneshr@...com>, Geert Uytterhoeven
	<geert@...ux-m68k.org>
CC: Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>, Rob Herring
	<robh+dt@...nel.org>, Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
	Yazan Shhady <yazan.shhady@...id-run.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 4/4] arm64: dts: ti: hummingboard-t: add overlays for
 m.2 pci-e and usb-3

Hi Geert, Vignesh,

Am 28.10.24 um 16:31 schrieb Vignesh Raghavendra:
>
> On 25/10/24 19:27, Geert Uytterhoeven wrote:
>> Hi Josua,
>>
>> On Mon, Feb 19, 2024 at 4:05 PM Josua Mayer <josua@...id-run.com> wrote:
>>> HummingBoard-T features two M.2 connectors labeled "M1" and "M2".
>>> The single SerDes lane of the SoC can be routed to either M1 pci-e
>>> signals, or M2 usb-3 signals by a gpio-controlled mux.
>>>
>>> Add overlays for each configuration.
>>>
>>> Signed-off-by: Josua Mayer <josua@...id-run.com>
>> Thanks for your patch, which is now commit bbef42084cc170cb ("arm64:
>> dts: ti: hummingboard-t: add overlays for m.2 pci-e and usb-3") in v6.9.
>>
>>> --- /dev/null
>>> +++ b/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dtso
>>> @@ -0,0 +1,44 @@
>>> +// SPDX-License-Identifier: GPL-2.0+
>>> +/*
>>> + * Copyright (C) 2023 Josua Mayer <josua@...id-run.com>
>>> + *
>>> + * Overlay for SolidRun AM642 HummingBoard-T to enable USB-3.1.
>>> + */
>>> +
>>> +/dts-v1/;
>>> +/plugin/;
>>> +
>>> +#include <dt-bindings/phy/phy.h>
>>> +
>>> +#include "k3-serdes.h"
>>> +
>>> +&serdes0 {
>>> +       #address-cells = <1>;
>>> +       #size-cells = <0>;
>>> +
>>> +       serdes0_link: phy@0 {
>>> +               reg = <0>;
>>> +               cdns,num-lanes = <1>;
>>> +               cdns,phy-type = <PHY_TYPE_USB3>;
>>> +               #phy-cells = <0>;
>>> +               resets = <&serdes_wiz0 1>;
>>> +       };
>>> +};
>>> +
>>> +&serdes_ln_ctrl {
>>> +       idle-states = <AM64_SERDES0_LANE0_USB>;
>>> +};
>>> +
>>> +&serdes_mux {
>>> +       idle-state = <0>;
>>> +};
>>> +
>>> +&usbss0 {
>>> +       /delete-property/ ti,usb2-only;
>> /delete-property/ (and /delete-node/) to delete something in the base DTS
>> does not work.

My understanding is that flags are equivalent to boolean, i.e:

ti,usb2-only = <true>;
ti,usb2-only;

are equivalent.

If so, can we assign <false> within the overlay?

> Geert,
>
> Thanks for the catching
Excellent spotting indeed.
I noticed this in passing about a week ago when I requested
Debian enable the necessary drivers in their distro kernel
(without understanding the root cause).
>
> Joshua,
>
> This overlay is pretty useless in light of above issue.  I intend to
> just drop this file unless you convince me otherwise?
>
I would really prefer to fix it, or somehow replace with equivalent functionality.

My original proposal was having the board a dtsi, and the pci and usb3
variants as standalone dts.