linux-kernel - Re: [PATCH] usb: dwc3: keystone: switch to use runtime pm

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Message-ID: <20140131221553.GF2502@saruman.home>
Date:	Fri, 31 Jan 2014 16:15:53 -0600
From:	Felipe Balbi <balbi@...com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
CC:	<balbi@...com>, Grygorii Strashko <grygorii.strashko@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<ivan.khoronzhuk@...com>, <linux-usb@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: keystone: switch to use runtime pm

Hi,

On Fri, Jan 31, 2014 at 02:20:48PM -0500, Santosh Shilimkar wrote:

[ snip ]

> > note that because of pm_runtime_set_active() that first
> > pm_runtime_get_sync() in probe() will simply increase the reference
> > counter without calling my ->runtime_resume() callback, which is exactly
> > what we want, as that would completely avoid situations of bad context
> > being restored because of that initial pm_runtime_get_sync().
> > 
> Thanks for making your point bit clear. 

no problem.

> > Then, we can even make pm_runtime completely async easily, because
> > clk_prepare() was called only on probe() (or before it, for that
> > matter).
> > 
> > Bottomline is, if you can guarantee me that clk_get(), clk_prepare(),
> > clk_enable() and pm_runtime_set_active() will be called properly before
> > my probe, i'll be more than happy to comply with your request above as
> > that will greatly simplify my driver.
> > 
> Which is the case at least I see on Keystone. And hence the patch from

I was going over pm_domain.c and drivers/base/power/clock_ops.c and none
of them enable pm_runtime or make sure pm_runtime_set_active() is
called.

> Grygorii works. I also noticed your proposal for wider platform to
> enforce above behavior which seems to be a good idea.

it'll take months to stabilize though ;-)

> > Just make, also, that if this clock is shared between dwc3-keystone
> > wrapper and dwc3 core, you clk_get() on both driver's probe.
> > 
> I understand. In summary, whichever patch you pick(yours) or Grygorii's,
> its completely safe to remove the clock handling from Keystone USB driver.

alright, since I can't really test, I'll take this as a true statement.
If there are any regressions I can blame you, hehehe.

cheers

-- 
balbi

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