linux-kernel - Re: [PATCH 4/4] net/smsc911x: Provide common clock functionality

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Date:	Fri, 21 Dec 2012 09:13:06 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Steve Glendinning <steve.glendinning@...well.net>,
	Robert Marklund <robert.marklund@...ricsson.com>,
	linus.walleij@...ricsson.com, arnd@...db.de,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/4] net/smsc911x: Provide common clock functionality

On Thu, 20 Dec 2012, Russell King - ARM Linux wrote:

> On Thu, Dec 20, 2012 at 08:35:14PM +0000, Lee Jones wrote:
> > On Thu, 20 Dec 2012, Russell King - ARM Linux wrote:
> > 
> > > On Thu, Dec 20, 2012 at 08:12:08PM +0100, Linus Walleij wrote:
> > > > On Wed, Dec 19, 2012 at 6:19 PM, Lee Jones <lee.jones@...aro.org> wrote:
> > > > 
> > > > > Some platforms provide clocks which require enabling before the
> > > > > SMSC911x chip will power on. This patch uses the new common clk
> > > > > framework to do just that. If no clock is provided, it will just
> > > > > be ignored and the driver will continue to assume that no clock
> > > > > is required for the chip to run successfully.
> > > > >
> > > > > Cc: Steve Glendinning <steve.glendinning@...well.net>
> > > > > Cc: netdev@...r.kernel.org
> > > > > Signed-off-by: Lee Jones <lee.jones@...aro.org>
> > > > 
> > > > Seems to me like it'll do the trick.
> > > > Acked-by: Linus Walleij <linus.walleij@...aro.org>
> > > 
> > > This looks fairly dangerous.  What about those platforms which use this
> > > driver, but don't provide a clock for it?
> > > 
> > > It looks like this will result in those platforms losing their ethernet
> > > support.  There's at least a bunch of the ARM evaluation boards which
> > > make use of this driver...
> > 
> > Right, but nothing should regress. If no clock is provided the driver
> > moves on during the request and will refuse to prepare, enable and
> > disable there after. 
> > 
> > Unless I've made a mistake somewhere? If so, I'd be happy to fixup.
> 
> No, but... don't use NULL for that.  Use IS_ERR(pdata->clk) instead.

I'm a bit confused. I do use IS_ERR, then if there was a problem
pdata->clk is set to NULL, then we test for NULL thereafter:

> /* Request clock */
> pdata->clk = clk_get(&pdev->dev, NULL);
> if (IS_ERR(pdata->clk)) {
>         netdev_warn(ndev, "couldn't get clock %d\n", PTR_ERR(pdata->clk));
>         pdata->clk = NULL;
> }

Are you saying remove "pdata->clk = NULL;" and test for IS_ERR
every time?

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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