linux-kernel - Re: [PATCH] i2c: qup: Fix order of runtime pm initialization

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Date:	Tue, 30 Sep 2014 13:03:30 -0700
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	Andy Gross <agross@...eaurora.org>
CC:	Wolfram Sang <wsa@...-dreams.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"Ivan T. Ivanov" <iivanov@...sol.com>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] i2c: qup: Fix order of runtime pm initialization

On Tue 30 Sep 12:59 PDT 2014, Andy Gross wrote:

> On Mon, Sep 29, 2014 at 06:53:24PM -0700, Bjorn Andersson wrote:
> > On Mon 29 Sep 15:00 PDT 2014, Andy Gross wrote:
> > 
> > > The runtime pm calls need to be done before populating the children via the
> > > i2c_add_adapter call.  If this is not done, a child can run into issues trying
> > > to do i2c read/writes due to the pm_runtime_sync failing.
> > > 
> > 
> > May I ask in what case this would fail?  I thought we tested this as we found
> > the faulty error check after calling pm_runtime_get_sync().
> 
> This is a different kind of failure.   If during probe, the children do some I2C
> activity, they will encounter issues with the runtime_sync due to the pm_runtime
> not being initialized.  However, once the qup probe completes, everything works
> fine.
> 
> The original runtime_sync issue revolved around the runtime_sync return value
> being misinterpreted due to the incorrect check.
> 

Yeah, I just wondered why my testing didn't trigger this. But I suspect that
the answer is simply that the client I ran with did not do i2c accesses from
probe.

Regards,
Bjorn
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