On Tue, 2011-11-22 at 13:11 +0000, Arnd Bergmann wrote:
> 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.
>
readl/writel won't work for big endian CPU when the registers are on a
bus that does the endian swabbing in hardware.
--Mark
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