linux-kernel - Re: [PATCH v6 15/28] ARM: tegra: Add usb-role-switch property to USB OTG ports

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Message-ID: <8c0defff-3348-6f97-6bd4-ddfc6117e707@gmail.com>
Date:   Wed, 15 Dec 2021 18:45:32 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        David Heidelberg <david@...t.cz>,
        Svyatoslav Ryhel <clamor95@...il.com>,
        Anton Bambura <jenneron@...tonmail.com>,
        Antoni Aloy Torrens <aaloytorrens@...il.com>,
        Nikola Milosavljevic <mnidza@...look.com>,
        Ion Agorria <ion@...rria.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Ihor Didenko <tailormoon@...bler.ru>,
        Andreas Westman Dorcsak <hedmoo@...oo.com>,
        Maxim Schwalm <maxim.schwalm@...il.com>,
        Raffaele Tranquillini <raffaele.tranquillini@...il.com>,
        Jasper Korten <jja2000@...il.com>,
        Thomas Graichen <thomas.graichen@...il.com>,
        Stefan Eichenberger <stefan.eichenberger@...adex.com>,
        Stefan Agner <stefan@...er.ch>,
        Peter Geis <pgwipeout@...il.com>, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 15/28] ARM: tegra: Add usb-role-switch property to USB
 OTG ports

15.12.2021 18:16, Thierry Reding пишет:
> On Wed, Dec 15, 2021 at 06:04:54PM +0300, Dmitry Osipenko wrote:
>> 15.12.2021 16:14, Thierry Reding пишет:
>>> On Sun, Dec 12, 2021 at 12:13:59AM +0300, Dmitry Osipenko wrote:
>>>> From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
>>>>
>>>> If an USB port is an OTG port, then we should add the usb-role-switch
>>>> property. Otherwise XUSB setup fails and therefore padctl is unable to
>>>> set up the ports. This leads to broken USB and PCIe ports. Add the
>>>> usb-role-switch properties to Tegra124 device-trees to fix the problem.
>>>>
>>>> The error message shown without this patch is e.g:
>>>> usb2-0: usb-role-switch not found for otg mode
>>>>
>>>> [digetx@...il.com: improved commit message]
>>>> Tested-by: Thomas Graichen <thomas.graichen@...il.com> # T124 Nyan Big
>>>> Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>> ---
>>>>  arch/arm/boot/dts/tegra124-apalis-v1.2.dtsi | 1 +
>>>>  arch/arm/boot/dts/tegra124-apalis.dtsi      | 1 +
>>>>  arch/arm/boot/dts/tegra124-nyan.dtsi        | 1 +
>>>>  arch/arm/boot/dts/tegra124-venice2.dts      | 2 +-
>>>>  4 files changed, 4 insertions(+), 1 deletion(-)
>>>
>>> The device tree bindings for the XUSB pad controller say that when this
>>> property is set, then the "connector" subnode should also exist.
>>>
>>> Any chance we can add that? I was planning on making that a dependency
>>> in the json-schema conversion of the binding, in which case it would be
>>> more of a "must" than a "should".
>>
>> I guess it will be harmless if you'll add the connector subnodes. Will
>> you be able to create a separate patch that will add the subnodes on top
>> of this patch?
>>
>> Thomas Graichen says that one USB port on Nyan Big doesn't work without
>> this patch. This is why this patch is needed essentially.
> 
> Okay, I can add "dummy" connector nodes for now. I don't see how we can
> properly set this up because as far as I can tell there's USB ID GPIO on
> Tegra124 (seems like it's a fixed function pin) and the VBUS GPIO is
> already used to enable the VBUS supply. The gpio-usb-b-connector binding
> required at least one of the ID and VBUS GPIOs to be specified.

The ID and VBUS hardware configurations are very board-specific. There
are multiple ways of how it could implemented on Tegra.

> On the other hand, at least Venice2 has a USB type A connector for this,
> so I'm not even sure how that would work. I vaguely recall that the
> Tegra20 Seaboard also had a USB type A and that it was possible to use
> it in device mode, but I don't how that would. Nor would it be correct
> to use the gpio-usb-b-connector compatible for that since, well, it's
> not USB type B.

I'm not sure whether it makes much sense to use OTG for USB type A
connectors, normally they should be fixed to host mode.

> I suspect that Apalis has a micro-B port, much like the Jetson TK1. My
> understanding is that OTG doesn't work on Jetson TK1 (which is why it's
> configured in "host" mode), so it'd be interesting to see if this can be
> made to work on Apalis.

Looks like the default Apalis carrier board has three type A connectors.

https://www.toradex.com/products/carrier-board/ixora-carrier-board