linux-kernel - Re: [PATCH v3 4/5] clk: basic gateable and fixed-rate clks

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Date:	Tue, 22 Nov 2011 13:11:00 +0000
From:	Arnd Bergmann <arnd.bergmann@...aro.org>
To:	Mike Turquette <mturquette@...com>
Cc:	linux@....linux.org.uk, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	jeremy.kerr@...onical.com, broonie@...nsource.wolfsonmicro.com,
	tglx@...utronix.de, linus.walleij@...ricsson.com,
	amit.kucheria@...aro.org, dsaxena@...aro.org, patches@...aro.org,
	linaro-dev@...ts.linaro.org, aul@...an.com,
	grant.likely@...retlab.ca, sboyd@...cinc.com,
	shawn.guo@...escale.com, skannan@...cinc.com,
	magnus.damm@...il.com, eric.miao@...aro.org,
	richard.zhao@...aro.org, Mike Turquette <mturquette@...aro.org>
Subject: Re: [PATCH v3 4/5] clk: basic gateable and fixed-rate clks

On Tuesday 22 November 2011, Mike Turquette wrote:
> +static void clk_hw_gate_set_bit(struct clk *clk)
> +{
> +       struct clk_hw_gate *gate = to_clk_hw_gate(clk);
> +       u32 reg;
> +
> +       reg = __raw_readl(gate->reg);
> +       reg |= BIT(gate->bit_idx);
> +       __raw_writel(reg, gate->reg);
> +}

You cannot rely on __raw_readl() to do the right thing, especially
in architecture independent code. The safe (but slightly inefficient)
solution would be readl/writel. For ARM-only code, it would be best
to use readl_relaxed()/writel_relaxed(), but most architectures do
not implement that. We can probably add a set of helpers in asm-generic/
to define them to the default functions, like "#define readl_relaxed(x)
readl(x)", which I think is a good idea anyway.

	Arnd
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