linux-kernel - Re: [PATCH 5/5] mmc: cavium: Fix probing race with regulator

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Date:   Tue, 16 May 2017 15:38:38 +0200
From:   Jan Glauber <jan.glauber@...iumnetworks.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        David Daney <david.daney@...ium.com>,
        Frank Rowand <frowand.list@...il.com>,
        "Steven J . Hill" <Steven.Hill@...ium.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] mmc: cavium: Fix probing race with regulator

On Tue, May 16, 2017 at 08:07:50AM -0500, Rob Herring wrote:
> On Tue, May 16, 2017 at 4:36 AM, Jan Glauber <jglauber@...ium.com> wrote:
> > If the regulator probing is not yet finished this driver
> > might catch a -EPROBE_DEFER. Returning after this condition
> > did not remove the created platform device. On a repeated
> > call to the probe function the of_platform_device_create
> > fails.
> >
> > Calling of_platform_device_destroy after EPROBE_DEFER resolves
> > this bug.
> >
> > Signed-off-by: Jan Glauber <jglauber@...ium.com>
> > ---
> >  drivers/mmc/host/cavium-thunderx.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/cavium-thunderx.c b/drivers/mmc/host/cavium-thunderx.c
> > index fe3d772..257535e 100644
> > --- a/drivers/mmc/host/cavium-thunderx.c
> > +++ b/drivers/mmc/host/cavium-thunderx.c
> > @@ -137,8 +137,10 @@ static int thunder_mmc_probe(struct pci_dev *pdev,
> >                                 continue;
> >
> >                         ret = cvm_mmc_of_slot_probe(&host->slot_pdev[i]->dev, host);
> > -                       if (ret)
> > +                       if (ret) {
> > +                               of_platform_device_destroy(&host->slot_pdev[i]->dev, NULL);
> 
> What if this fails after the 1st iteration of the loop. It's only
> cleaning up the current device.

The platform device is just a dummy device created directly before
cvm_mmc_of_slot_probe(). So there is no need to cleanup anything else.

As far as I've seen it the platform code 'tags' the nodes it already
used, but I need the same node to be parsed again on -EPROBE_DEFER.

> Use devm_of_platform_populate or
> of_platform_populate/of_platform_depopulate instead.

I'm not sure one of these will work here.

--Jan

> Rob