linux-kernel - Re: [PATCH stable-5.15 3/3] usb: dwc3: disable USB core PHY management

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Date:   Fri, 21 Oct 2022 08:54:24 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Stefan Agner <stefan@...er.ch>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan+linaro@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        stable <stable@...nel.org>, regressions@...ts.linux.dev,
        m.szyprowski@...sung.com, krzk@...nel.org
Subject: Re: [PATCH stable-5.15 3/3] usb: dwc3: disable USB core PHY
 management

On Fri, Oct 21, 2022 at 12:06:12AM +0200, Stefan Agner wrote:
> On 2022-10-19 10:59, Johan Hovold wrote:
> > On Tue, Oct 18, 2022 at 05:27:24PM +0200, Stefan Agner wrote:
> >> On 2022-09-06 14:07, Johan Hovold wrote:
> >> > From: Johan Hovold <johan+linaro@...nel.org>
> >> >
> >> > commit 6000b8d900cd5f52fbcd0776d0cc396e88c8c2ea upstream.
> >> >
> >> > The dwc3 driver manages its PHYs itself so the USB core PHY management
> >> > needs to be disabled.
> >> >
> >> > Use the struct xhci_plat_priv hack added by commits 46034a999c07 ("usb:
> >> > host: xhci-plat: add platform data support") and f768e718911e ("usb:
> >> > host: xhci-plat: add priv quirk for skip PHY initialization") to
> >> > propagate the setting for now.

> >> For some reason, this commit seems to break detection of the USB to
> >> S-ATA controller on ODROID-HC1 devices (Exynos 5422).

> > I think this may be related to the calibration calls added to dwc3 and
> > later removed again by commits:
> > 
> > 	d8c80bb3b55b ("phy: exynos5-usbdrd: Calibrate LOS levels for exynos5420/5800")
> > 	a0a465569b45 ("usb: dwc3: remove generic PHY calibrate() calls")
> > 
> > The removal explicitly mentions that the expectation is that USB core
> > will do the PHY calibration.
> > 
> > There could be other changes in the sequencing of events that this
> > platform has been implicitly relying on, but as a start, could try
> > adding the missing calibration calls (patch below) and see if that makes a
> > difference?
> 
> The patch below did not apply to 5.15.74 directly, but I think I was
> able to get the corrected patch applied (see below)

Looks good to me.

> That said, I do not have direct access to that hardware, but I created a
> build and asked the user test it.

Thanks, let me know how it goes.

Johan