linux-kernel - Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

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Message-ID: <20120925110703.GN31374@n2100.arm.linux.org.uk>
Date:	Tue, 25 Sep 2012 12:07:03 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Felipe Balbi <balbi@...com>
Cc:	"Poddar, Sourav" <sourav.poddar@...com>,
	gregkh@...uxfoundation.org, khilman@...com, paul@...an.com,
	tony@...mide.com, linux-kernel@...r.kernel.org,
	santosh.shilimkar@...com, linux-serial@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	alan@...ux.intel.com
Subject: Re: [RFT/PATCH] serial: omap: prevent resume if device is not
	suspended.

On Tue, Sep 25, 2012 at 01:37:03PM +0300, Felipe Balbi wrote:
> On Tue, Sep 25, 2012 at 11:29:58AM +0100, Russell King - ARM Linux wrote:
> > Because you are accusing me of potentially breaking your beagleboard
> > for merely suggesting further investigation and a better commit message.
> 
> Where did I accuse you of anyting ? I just mentioned we experienced a
> regression with beagleboard XM when using pm_runtime_set_active().

I quote:
:> But should we cause a regression to beagleboard XM because of that ?
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I say again: I was _only_ suggesting further investigation, yet you
were mouthing off about causing a regression to beagleboard "because
of that", effectively saying that no, we should not do any further
investigation and this is the only fix.

> To add extra info, here you go:

Finally, something constructive.

> We pinged Paul and asked if he had seen that before, he had no
> pointers... Because Documentation/power/runtime_pm.txt was using a
> mystruct->is_suspended flag, we just decided to follow the same
> "design" since no-one was able to suggest why pm_runtime_set_active()
> was breaking beagleXM nor how it was supposed to actually work.
> 
> Reading the code: pm_runtime_set_active() would tell pm_runtime core
> the device is actually active by setting runtime_status to RPM_ACTIVE,
> thus the following pm_runtime_get_sync() wouldn't actually call
> runtime_resume() callback, but it would increment usage_counter.
> 
> I can't see why this would fail on beagleXM, but it does and we'd like
> to hear in which situations this could fail...

Well, I've just spent five minutes analysing the code paths - which I
hadn't looked at before - and I've pointed out what's probably causing
the problem for Beagle.  I think you owe me an appology over your
aggressive attitude towards my suggestions that there needed to be
some further investigation.
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