linux-kernel - Re: [v2] musb: omap2430: do not assume balanced enable()/disable()

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Date:   Fri, 9 Sep 2016 13:51:04 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Andreas Kemnade <andreas@...nade.info>, Bin Liu <b-liu@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v2] musb: omap2430: do not assume balanced enable()/disable()

* Laurent Pinchart <laurent.pinchart@...asonboard.com> [160909 13:21]:
> On Friday 09 Sep 2016 13:08:03 Tony Lindgren wrote:
> > This patch has a side effect of fixing the issue by breaking PM
> > runtime, not a good fix as discussed.
> 
> How exactly is it worse breaking runtime PM than breaking USB gadget 
> completely ? :-)

Yeah sorry to break it, I obviously did not test it on all platforms :(
I'm mostly using omap3 with the 2430 glue layer and am335x for the
dsps glue layer and did not know that omap4 is broken. I guess I've
recently just used the EHCI ports on panda.

> The issue here is that the .disable() platform operation is called by musb 
> with the PHY already powered off, leading to the PHY power reference count 
> becoming negative. The next call to the .enable() operation restores the 
> reference count to 0 without enabling the PHY.

Well for the phy-twl4030-usb.c, AFAIK the right fix is to fix the PHY
driver as done in "[PATCH v2] phy-twl4030-usb: initialize charging-related
stuff via pm_runtime". I suspect something similar is happening here
also with the omap4 legacy phy.

> Feel free to send me a better fix and I will test it.

Yeah will do, hang on.

Tony