linux-kernel - Re: [PATCH] soc: qcom: pmic

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Date:   Thu, 14 Dec 2023 16:04:49 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Rob Clark <robdclark@...il.com>, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: qcom: pmic_glink: Fix boot when QRTR=m

On Thu, 14 Dec 2023 at 16:01, Johan Hovold <johan@...nel.org> wrote:
>
> On Thu, Dec 14, 2023 at 01:04:43PM +0200, Dmitry Baryshkov wrote:
> > On Thu, 14 Dec 2023 at 09:16, Johan Hovold <johan@...nel.org> wrote:
> > >
> > > On Wed, Dec 13, 2023 at 01:06:43PM -0800, Rob Clark wrote:
> > > > From: Rob Clark <robdclark@...omium.org>
> > > >
> > > > We need to bail out before adding/removing devices, if we are going
> > > > to -EPROBE_DEFER.  Otherwise boot will get stuck forever at
> > > > deferred_probe_initcall().
> > >
> > > Can please you expand on why this is a problem here in the commit
> > > message?
> > >
> > > The aux devices appear to be tore down correctly in the probe error
> > > paths so how exactly does that lead to deferred_probe_initcall() being
> > > stuck? This sounds like we may have a problem elsewhere which this patch
> > > is papering over.
> >
> > This is a known problem. Successful probes during the probe deferral
> > loop causes the whole loop to be reiterated. Creating child devices
> > usually results in  a successful probe. Aso I thought that just
> > creating new device also causes a reprobe, but I can not find any
> > evidence now.
>
> This still needs to be described in the commit message.
>
> Only a successful probe should trigger a reprobe, and when the child
> devices are registered the parent is not yet on the deferred probe list.
> So something is not right or missing here.

Child devices can be successfully probed, then the parent gets
-EPROBE_DEFER, removes children and then it goes on and on.

-- 
With best wishes
Dmitry