linux-kernel - Re: [PATCH v3] usb: chipidea: Grab the (legacy) USB PHY by phandle first

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Date:   Thu, 21 Feb 2019 11:48:37 +0100
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Peter Chen <peter.chen@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3] usb: chipidea: Grab the (legacy) USB PHY by phandle
 first

Hi,

On Thu, 2019-02-21 at 09:30 +0000, Peter Chen wrote:
>  
> > > Current code w/o your patch, it is possible both ci->phy and
> > > ci->usb_phy are valid if the USB PHY is not at the device tree, but generic PHY is
> > at the device tree.
> > > If you don't want to fix this issue with this patch, it is ok too. We could fix it later.
> > 
> > I'm not sure I understand the issue. With my patch, if there is a generic PHY
> > described in device-tree, then devm_usb_get_phy_by_phandle for legacy PHY will
> > fail and the code will fallback to devm_usb_get_phy, which is the same behavior as
> > before.
> > 
> 
> You are right, but this behavior is incorrect since each controller has only one physical
> USB PHY.
> 
> > Is it a problem that we can end up with both a generic and legacy PHY?
> > I thought this was expected behavior at probe, and the rest of the code will just use
> > the generic one in priority.
> > 
> > Do you want to make it so that only one (generic or legacy) PHY remains after
> > probe?
> > 
>  
> Yes, I just want only one valid, either ci->phy or ci->usb_phy, it makes sense.

Sounds good to me. I'll send out v4 with this patch and an extra one to
refactor the PHY selection path and only attempt to get a single PHY.

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com