linux-kernel - Re: [PATCH 1/5] clk: berlin: add common pll driver

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Message-ID: <20151001223220.GQ19319@codeaurora.org>
Date:	Thu, 1 Oct 2015 15:32:20 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Jisheng Zhang <jszhang@...vell.com>
Cc:	sebastian.hesselbarth@...il.com, catalin.marinas@....com,
	will.deacon@....com, mark.rutland@....com, robh+dt@...nel.org,
	pawel.moll@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] clk: berlin: add common pll driver

On 09/22, Jisheng Zhang wrote:
> diff --git a/drivers/clk/berlin/pll.c b/drivers/clk/berlin/pll.c
> new file mode 100644
> index 0000000..9aad0b6
> --- /dev/null
> +++ b/drivers/clk/berlin/pll.c
> @@ -0,0 +1,119 @@
> +
> +#define to_berlin_pll(hw)       container_of(hw, struct berlin_pll, hw)
> +
> +static u8 vcodiv_berlin[] = {1, 2, 4, 8, 16, 32, 64, 128};

This is an array of 1 << index position...

> +
> +static unsigned long berlin_pll_recalc_rate(struct clk_hw *hw,
> +					    unsigned long parent_rate)
> +{
> +	u32 val, fbdiv, rfdiv, vcodivsel, bypass;
> +	struct berlin_pll *pll = to_berlin_pll(hw);
> +
> +	bypass = readl_relaxed(pll->bypass);
> +	if (bypass & (1 << pll->bypass_shift))
> +		return parent_rate;
> +
> +	val = readl_relaxed(pll->ctrl + PLL_CTRL0);
> +	fbdiv = (val >> 12) & 0x1FF;
> +	rfdiv = (val >> 3) & 0x1FF;
> +	val = readl_relaxed(pll->ctrl + PLL_CTRL1);
> +	vcodivsel = (val >> 9) & 0x7;
> +	return parent_rate * fbdiv * 4 / rfdiv /
> +		vcodiv_berlin[vcodivsel];

so we can replace this with 1 << vcodivsel?

> +}
> +
> +static u8 berlin_pll_get_parent(struct clk_hw *hw)
> +{
> +	struct berlin_pll *pll = to_berlin_pll(hw);
> +	u32 bypass = readl_relaxed(pll->bypass);
> +
> +	if (bypass & (1 << pll->bypass_shift))
> +		return 1;
> +	else
> +		return 0;

Simplify this to 

	if (bypass & (1 << pll->bypass_shift))
		return 1;
	return 0;

or

	return !!(bypass & (1 << pll->bypass_shift)) 

> +}
> +
> +static const struct clk_ops berlin_pll_ops = {
> +	.recalc_rate	= berlin_pll_recalc_rate,
> +	.get_parent	= berlin_pll_get_parent,
> +};
> +
> +void __init berlin_pll_setup(struct device_node *np)

static?

> +{
> +	struct clk_init_data init;
> +	struct berlin_pll *pll;
> +	const char *parent_names[PLL_SOURCE_MAX];
> +	struct clk *clk;
> +	int ret, num_parents;
> +
> +	num_parents = of_clk_get_parent_count(np);
> +	if (num_parents <= 0 || num_parents > PLL_SOURCE_MAX)
> +		return;
> +
> +	of_clk_parent_fill(np, parent_names, num_parents);
> +
> +	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
> +	if (WARN_ON(!pll))

We already print a big warning on allocation failures, so drop
the WARN_ON please.

> +		return;
> +
> +	pll->ctrl = of_iomap(np, 0);
> +	pll->bypass = of_iomap(np, 1);
> +	ret = of_property_read_u8(np, "bypass-shift", &pll->bypass_shift);
> +	if (WARN_ON(!pll->ctrl || !pll->bypass || ret))
> +		return;
> +
> +	init.name = np->name;
> +	init.ops = &berlin_pll_ops;
> +	init.parent_names = parent_names;
> +	init.num_parents = num_parents;

init.flags is not initialized. Please initialize the init struct
on the stack to 0 to avoid future problems.

> +
> +	pll->hw.init = &init;
> +
> +	clk = clk_register(NULL, &pll->hw);
> +	if (WARN_ON(IS_ERR(clk)))
> +		return;
> +
> +	ret = of_clk_add_provider(np, of_clk_src_simple_get, clk);
> +	if (WARN_ON(ret))
> +		return;

This return is useless.

> +}

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