linux-kernel - Re: [PATCH 5/8] ARM: zynq: add COMMON

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Message-ID: <20121102133850.GO5190@beefymiracle.amer.corp.natinst.com>
Date:	Fri, 2 Nov 2012 07:38:50 -0600
From:	Josh Cartwright <josh.cartwright@...com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Mike Turquette <mturquette@...com>,
	John Stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Linn <John.Linn@...inx.com>,
	Michal Simek <michal.simek@...inx.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-serial@...r.kernel.org,
	Michal Simek <monstr@...str.eu>
Subject: Re: [PATCH 5/8] ARM: zynq: add COMMON_CLK support

Thanks for the review.

On Fri, Nov 02, 2012 at 10:33:44AM +0100, Lars-Peter Clausen wrote:
> On 10/31/2012 07:58 PM, Josh Cartwright wrote:
> > [...]
> > +#define PERIPH_CLK_CTRL_SRC(x)	(periph_clk_parent_map[((x)&3)>>4])
> > +#define PERIPH_CLK_CTRL_DIV(x)	(((x)&0x3F00)>>8)
> 
> A few more spaces wouldn't hurt ;)

Okay, sure.

> > [...]
> > +static void __init zynq_periph_clk_setup(struct device_node *np)
> > +{
> > +	struct zynq_periph_clk *periph;
> > +	const char *parent_names[3];
> > +	struct clk_init_data init;
> > +	struct clk *clk;
> > +	int err;
> > +	u32 reg;
> > +	int i;
> > +
> > +	err = of_property_read_u32(np, "reg", &reg);
> > +	WARN_ON(err);
>
> Shouldn't the function abort if a error happens somewhere? Continuing here
> will lead to undefined behavior. Same is probably true for the other WARN_ONs.

The way I see it is: the kernel is will be left in a bad state in the
case of any failure, regardless of if we bail out or continue.  AFAICT,
there is no clean way to recover from a failure this early.

Given that, it seems simpler (albeit marginally so) just to continue; so
that's what I chose to do.  I'm not opposed to bailing out, just not
convinced it does anything for us.

> > +
> > +	periph = kzalloc(sizeof(*periph), GFP_KERNEL);
> > +	WARN_ON(!periph);
> > +
> > +	periph->clk_ctrl = slcr_base + reg;
> > +	spin_lock_init(&periph->clkact_lock);
> > +
> > +	init.name = np->name;
> > +	init.ops = &zynq_periph_clk_ops;
> > +	for (i = 0; i < ARRAY_SIZE(parent_names); i++)
> > +		parent_names[i] = of_clk_get_parent_name(np, i);
> > +	init.parent_names = parent_names;
> > +	init.num_parents = ARRAY_SIZE(parent_names);
> > +
> > +	periph->hw.init = &init;
> > +
> > +	clk = clk_register(NULL, &periph->hw);
> > +	WARN_ON(IS_ERR(clk));
> > +
> > +	err = of_clk_add_provider(np, of_clk_src_simple_get, clk);
> > +	WARN_ON(err);
> > +
> > +	for (i = 0; i < 2; i++) {
> 
> Not all of the peripheral clock generators have two output clocks. I think
> it makes sense to use the number entries in clock-output-names here.

Yes, I agree.  I'll also update the bindings documentation.

Thanks again,
  Josh
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