linux-kernel - Re: [PATCH 2/3] PWM: vt8500: Update vt8500 PWM driver support

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Date:	Mon, 22 Oct 2012 20:09:07 +1300
From:	Tony Prisk <linux@...sktech.co.nz>
To:	Thierry Reding <thierry.reding@...onic-design.de>
Cc:	devicetree-discuss@...ts.ozlabs.org, arm@...nel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] PWM: vt8500: Update vt8500 PWM driver support

On Mon, 2012-10-22 at 19:51 +1300, Tony Prisk wrote:
> > 
> > >  	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> > >  	if (chip == NULL) {
> > >  		dev_err(&pdev->dev, "failed to allocate memory\n");
> > > @@ -123,26 +144,32 @@ static int __devinit pwm_probe(struct platform_device *pdev)
> > >  	chip->chip.ops = &vt8500_pwm_ops;
> > >  	chip->chip.base = -1;
> > >  	chip->chip.npwm = VT8500_NR_PWMS;
> > > +	chip->clk = of_clk_get(np, 0);
> > 
> > I thought this was supposed to work transparently across OF and !OF
> > configurations by using just clk_get() or devm_clk_get()? I guess that
> > if the driver depends on OF, then this would be moot, but we should
> > probably stick to the standard usage anyway.
> > 
> > Furthermore, of_clk_get() doesn't seem to be managed, so you'd need to
> > add explicit clk_put() in the error cleanup paths. One more argument in
> > favour of using devm_clk_get() instead.
> 
> Hmm good point. I stuck with of_ functions because its an OF only driver
> and it seemed 'backward' to mix old code with new. It does pose the
> question of 'why have of_clk_get() if existing functions work better'.

Was about to fix this but noticed why it wasn't like this to start
with :)

struct clk *devm_clk_get(struct device *dev, const char *id);
struct clk *of_clk_get(struct device_node *np, int index);

devm_clk_get requires me to 'get' the clock by name. arch-vt8500 (and I
believe a lot of other arch's) don't enforce names for clocks defined in
devicetree, therefore there is no way for me to know what name the clk
has unless I include in the binding that the clock must be named 'xxx'.

of_clk_get retrieves it by the dt-node + index, so it doesn't care as
long as its the 1st clock listed.


Welcome your feedback.

Regards
Tony P

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