linux-kernel - Re: [PATCH 2/2] fpga-manager: Add Socfpga Arria10 support

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Message-ID: <20160712222029.GW1041@n2100.armlinux.org.uk>
Date:	Tue, 12 Jul 2016 23:20:29 +0100
From:	Russell King - ARM Linux <linux@...linux.org.uk>
To:	Moritz Fischer <moritz.fischer@...us.com>
Cc:	Alan Tull <atull@...nsource.altera.com>,
	Mark Rutland <mark.rutland@....com>,
	Devicetree List <devicetree@...r.kernel.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Alan Tull <delicious.quinoa@...il.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] fpga-manager: Add Socfpga Arria10 support

On Tue, Jul 12, 2016 at 02:31:05PM -0700, Moritz Fischer wrote:
> On Tue, Jul 12, 2016 at 12:07 PM, Alan Tull <atull@...nsource.altera.com> wrote:
> > +       priv->clk = devm_clk_get(dev, NULL);
> > +       if (IS_ERR(priv->clk)) {
> > +               dev_err(dev, "no clock specified\n");
> > +               return PTR_ERR(priv->clk);
> > +       }
> > +
> > +       ret = clk_prepare_enable(priv->clk);
> > +       if (ret) {
> > +               dev_err(dev, "could not enable clock\n");
> > +               clk_put(priv->clk);
> 
> Seen that you used devm_clk_get() is this one necessary?

That's actually a bug.  Never clk_put() a devm_clk_get()'d clock.
devm_clk_put() is what you want if provided.  However, I think
this clk_put() call is useless here.

> > +static int socfpga_a10_fpga_remove(struct platform_device *pdev)
> > +{
> > +       struct fpga_manager *mgr = platform_get_drvdata(pdev);
> > +       struct a10_fpga_priv *priv = mgr->priv;
> > +
> > +       fpga_mgr_unregister(&pdev->dev);
> > +       clk_disable_unprepare(priv->clk);
> > +       clk_put(priv->clk);
> 
> Same here, if needed at all shouldn't it be devm_clk_put() ?

And also useless here, as the whole point of the devm_* stuff is to
clean up the resources that were claimed on probe failure or when
the device is unbound from its driver.

-- 
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