linux-kernel - Re: [PATCH v3 3/9] arm64: dts: amlogic: Used onboard usb hub reset on odroid c2

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Message-ID: <ZM7jtD2rniWAexVZ@Dell-Inspiron-15>
Date:   Sat, 5 Aug 2023 20:05:08 -0400
From:   Ben Wolsieffer <benwolsieffer@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Anand Moon <linux.amoon@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org,
        Matthias Kaehlcke <mka@...omium.org>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        Johan Hovold <johan@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/9] arm64: dts: amlogic: Used onboard usb hub reset
 on odroid c2

On Sat, Aug 05, 2023 at 11:30:21PM +0200, Krzysztof Kozlowski wrote:
> On 02/08/2023 23:06, Ben Wolsieffer wrote:
> > 
> > Hello,
> > 
> > This patch breaks USB support on the ODROID-C2. As soon as the
> > onboard_usb_hub module is loaded, all USB devices disconnect.
> > Blacklisting onboard_usb_hub makes USB work as expected.
> > 
> > I tried to reproduce the problem by manually toggling the reset line,
> > but the problem seems to be specific to this driver. When reset is
> > asserted manually, the devices disconnect, but they all enumerate again
> > as soon as reset is released.
> > 
> > Also, I have been unable to make USB work again (until the next reboot)
> > even after unloading onboard_usb_hub.
> 
> Wasn't this patch made exactly to fix USB support, not break it? I might
> be missing something but maybe this was not tested at all?
> 
> Best regards,
> Krzysztof
>

I have been using USB on the ODROID-C2 for several years without issues.
It looks to me that this patch was designed to make reset control for
the hub more elegant, rather than fix a specific issue. The same change
was applied to several devices, so it seems plausible that it was not
tested on all of them.

Thanks, Ben