> From: Peter Chen
...
> > > >> +#ifdef CONFIG_SOC_IMX28
> > > >> +static inline void imx28_ehci_writel(const unsigned int val,
> > > >> + volatile __u32 __iomem *addr)
> > > >> +{
> > > >> + __asm__ ("swp %0, %0, [%1]" : : "r"(val), "r"(addr));
> > > >> +}
> > > >> +#else
> > > >> +static inline void imx28_ehci_writel(const unsigned int val,
> > > >> + volatile __u32 __iomem *addr)
> > > >> +{
> > > >> +}
> > > >> +#endif
If you replace the above with:
#define imx28_ehci_writel(v, a) writel(v, a)
> > > >> static inline void ehci_writel(const struct ehci_hcd *ehci,
> > > >> const unsigned int val, __u32 __iomem *regs)
> > > >> {
> > > >> @@ -736,7 +749,10 @@ static inline void ehci_writel(const struct
> > > >> ehci_hcd *ehci,
> > > >> writel_be(val, regs) :
> > > >> writel(val, regs);
> > > >> #else
> > > >> - writel(val, regs);
> > > >> + if (IS_ENABLED(CONFIG_SOC_IMX28) && ehci->imx28_write_fix)
> > > >> + imx28_ehci_writel(val, regs);
> > > >> + else
> > > >> + writel(val, regs);
> > > >> #endif
> > > >
> > > > This IS_ENABLED() isn't needed at all, so please remove it.
> > >
> > > It's an optimisation for the hot path, if kernel isn't build for a mx28
> > > the newly added if() is completely optimized out. The same argument
> > > applies to the next patch.
> >
> > If the kernel isn't built for mx28 then the if statment goes away
> > without the IS_ENABLED() call as well, due to the empty inline
> > function, right?
> >
>
> With IS_ENABLED(), the non-imx28 platform don't need to judge the
> condition of ehci->imx28_write_fix, if you don't think we need
> to care one or two instructions for every other platforms, I can
> delete it.
I think the compiler might optimise out the conditional (because the
then and else clauses are identical.
Also the earlier #if - for big-endian - can be removed.
The compiler already collapses it down.
David
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