Re: [PATCH v3 03/12] usb: ehci-hcd: notify phy when connect change

On Tue, 5 Jun 2012, Marek Vasut wrote:

quoted

quoted

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Do the tests in the opposite order and add "unlikely":
			if (unlikely(ehci->transceiver &&
			
					(pstatus & PORT_CSC)) {

That way it will fail more quickly on systems where it doesn't apply or
for unaffected ports.

Does this unlikely() have any effect on ARM/MIPS/PPC, where this chipidea
IP is used ? Or is there some x86 device sporting this IP too?

I don't know what unlikely() does on architectures other than x86.

It should be optimized out to nothing on anything else but x86. On x86 it is a 
hint for the branch predictor. Or that's what I believe it is.

That's right.  Then it should have no effect on ARM/MIPS/PPC.

quoted

And
I haven't heard of any x86 systems that would need to use this code.

On the other hand, port-status changes don't occur very frequently.  A
little time penalty one way or the other won't make much difference.

I'm not opposed, just curious :)

No big deal either way.  But the order of the tests should be switched, 
because on most systems, ehci->transceiver will be NULL.

Alan Stern

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