linux-kernel - Re: [PATCH 0/3] USB: musb: dsps: phy fix and DT-topology support

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Message-ID: <20180418185613.GH14921@uda0271908>
Date:   Wed, 18 Apr 2018 13:56:13 -0500
From:   Bin Liu <b-liu@...com>
To:     Johan Hovold <johan@...nel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Arnd Bergmann <arnd@...db.de>,
        Kishon Vijay Abraham I <kishon@...com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] USB: musb: dsps: phy fix and DT-topology support

On Wed, Apr 18, 2018 at 08:46:40PM +0200, Johan Hovold wrote:
> On Wed, Apr 18, 2018 at 11:20:15AM -0500, Bin Liu wrote:
> > Johan,
> > 
> > On Fri, Apr 13, 2018 at 05:15:02PM +0200, Johan Hovold wrote:
> > > I've been carrying a patch out-of-tree since my work on improving the
> > > USB device-tree support which is needed to be able to describe USB
> > > topologies for musb based controllers.
> > > 
> > > This patch, which associates the platform controller device with the
> > > glue device device-tree node, did not play well with the recent changes
> > > which added generic phy support to USB core however.
> > > 
> > > Like the recent dwc2 regression fixed by Arnd after the device-tree
> > > #phy-cell changes, the generic phy code in USB core can now also fail
> > > indefinitly with -EPROBE_DEFER when the controller uses a legacy USB
> > > phy.
> > > 
> > > The second patch addresses this for musb, which handles its own (legacy
> > > and generic) phys, but something more may possibly now be needed for
> > > other platforms with legacy phys.
> > > 
> > > In the process of debugging this, I stumbled over another issue which
> > > caused the dsps legacy phy init two be called twice on every probe and
> > > which is fixed by the first patch.
> > > 
> > > Johan
> > > 
> > > 
> > > Johan Hovold (3):
> > >   USB: musb: dsps: drop duplicate phy initialisation
> > >   USB: musb: host: prevent core phy initialisation
> > 
> > Are the two bugs only affecting you with your out-of-tree patch? It
> > seems don't have any functional impact for me. I need to make a decision
> > if these two patches need to go to the stable trees...
> 
> The first bug is independent of the third patch (the "out-of-tree"
> patch), but as Uwe also noted it seems to be mostly benign since it took
> two years for it to be discovered. For that reason, and to minimise the
> risk of any stable regressions, I did not mark it for stable.
> 
> The second fix is really only needed with the third of_node patch since
> I don't think any of the glue drivers propagates the device-tree node in
> this way currently. Hence it could also wait for 3.18, and it is in any
> case not stable material as the generic-phy support in USB core is new
> in 3.17.

Great, thanks for confirming. I will not send them for stable trees.

> 
> Note that other host controllers may have a device-tree node with
> associated legacy-phys however and that this could now lead to similar
> problems starting with 3.17.

regards,
-Bin.