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: <533c54e5-d024-4fd0-b92d-0f320f25999f@solid-run.com>
Date: Wed, 30 Oct 2024 12:18:15 +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

Am 28.10.24 um 19:44 schrieb Vignesh Raghavendra:
>
> On 28/10/24 22:49, Josua Mayer wrote:
>> 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.
>>
>
> Yeah, you would need a separate board dts for this profile. Please
> propose a patch
Is there any chance of reassigning <false> and making an argument
that this should be fixed?

I find it frustrating that overlays can't override boolean properties,
and for consistency reasons I would otherwise change both
pcie and usb3 overlays to standalone dts.