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

Andreas Kemnade andreas at kemnade.info
Tue Aug 9 07:35:59 CEST 2016

On Fri, 5 Aug 2016 23:21:35 -0700
Tony Lindgren <tony at atomide.com> wrote:

> * Andreas Kemnade <andreas at kemnade.info> [160805 08:35]:
> > I repeat the subject line of the patch:
> > [PATCH v2] musb: omap2430: do not assume balanced enable()/disable()
> > It is *not* fix charging.
> > 
> > So you mean that the phy should magically know at which refcounter
> > it should power on and off if power on/off is not called in the
> > balanced way?
> No, I mean we need to figure out why things can be called in
> unbalanced way. With your patch I end up with unbalanced calls
> leaving the phy on after all the modules have been removed :)
Well, causing trouble when modules are removed was not the intention.
I was just happy to have things working a bit again.
The phy is powered on/off via

Calls to musb_platform_enable() occur at only 1 place.
musb_platform_disable() is called at 4 places.

about balancing:
There is musb_start() and musb_stop(). They are called from
These call musb_platform_enable() and musb_platform_disable().
Looks ok.

There is musb_suspend() and musb_resume():

musb_suspend() calls musb_platform_disable()
musb_resume() calls musb_plaform_enable() via musb_start()
looks balanced but why don't we use musb_stop() in musb_suspend()?

Now the odd things:
musb_platform_disable() in musb_remove() called upon module removal
musb_platform_disable() in musb_init_controller() called from

This looks clearly unbalanced.

> > Maybe the phy-twl4030 uses the phy layer wrong. 
> > Now the relevant part of power on/off in phy-twl4030 is done via
> > struct phy_ops.power_off/power_on (*not* via pm_runtime). Maybe
> > that is wrong and more parts should be moved to the pm_runtime
> > stuff (which is also present). 
> We should use phy power_off/power_on for the USB related parts.
> The parts needed by other components, like VBUS detection, should
> be handled by PM runtime. We should get phy-twl4030-usb and the
> charger driver working also when no musb modules are loaded.
> > Then the phy subsystem has its own power refcounter in struct
> > phy.power_count. It it handled via phy_power_off()/phy_power_on().
> > And that is called from musb/omap2430.c 
> > But that is another story. 
> Yes that's what the USB driver is expected to do. But obviously
> there are issues remaining also in the phy-twl4030-usb.c driver.
> And it seems that we should have some OTG parts always enabled
> when VBUS is detected when twl4030-charger is configured?
Seems so. I am writing a patch for it.

> > > If there are MUSB specific PM runtime issues then let's fix
> > > those separately.
> > > 
> > And that exactly tries my patch to do. For that task it does not
> > even use the PM runtime system. Again please read the subject line
> > of the patch. Maybe it unveils some other pm issues in musb
> > which should first be fixed in a complete patch series.
> Certainly that needs to be fixed, but let's do it in a way where
> things work for other test cases also. Care to describe how to
> to reproduce the issue you're seeing? It seems that you are
> seeing devices not being enmerated leading to the charger not
> working? Is this with built in MUSB and phy modules?
Both as modules. I added some debug output to the driver/phy/phy-core.c
and have seen the phy->power_count sticking at -1 or 0. 
g_ether is also loaded.
Gadget stops for me (device not showing up at the other side) at 4.7rc4.
But I remember Nikolaus having the situation on the same type of device
that it was important on which side you replug the usb cable
(probably causing some timing differences) with 4.7rc1.

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