-----Original Message-----
From: Robin Murphy [mailto:robin.murphy at arm.com]
Sent: Monday, August 01, 2016 10:53 PM
To: ???(LEE KWANGWOO) MS SW; Russell King - ARM Linux; Catalin Marinas; Will Deacon; Mark Rutland;
linux-arm-kernel at lists.infradead.org
Cc: ???(KIM HYUNCHUL) MS SW; linux-kernel at vger.kernel.org; ???(CHUNG WOO SUK) MS SW
Subject: Re: [PATCH v2] arm64: mm: convert __dma_* routines to use start, size

On 01/08/16 14:36, Robin Murphy wrote:

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On 01/08/16 00:45, kwangwoo.lee at sk.com wrote:
[...]

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-----8<-----

diff --git a/arch/arm64/include/asm/assembler.h

b/arch/arm64/include/asm/assembler.h
index 10b017c4bdd8..1c005c90387e 100644

--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h

@@ -261,7 +261,16 @@ lr	.req	x30		// link register
 	add	\size, \kaddr, \size
 	sub	\tmp2, \tmp1, #1
 	bic	\kaddr, \kaddr, \tmp2
-9998:	dc	\op, \kaddr
+9998:
+	.ifeqs "\op", "cvac"
+alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE
+	dc	cvac, \kaddr
+alternative_else
+	dc	civac, \kaddr
+alternative_endif
+	.else
+	dc	\op, \kaddr
+	.endif
 	add	\kaddr, \kaddr, \tmp1
 	cmp	\kaddr, \size
 	b.lo	9998b

I agree that it looks not viable because it makes the macro bigger and
conditional specifically with CVAC op.

Actually, having had a poke around in the resulting disassembly, it
looks like this does work correctly. I can't think of a viable reason
for the whole dcache_by_line_op to ever be wrapped in yet another
alternative (which almost certainly would go horribly wrong), and it
would mean that any other future users are automatically covered for
free. It's just horrible to look at at the source level.

Then, Are you going to send a patch for this? Or should I include this change?

I'll do a bit more testing just to make sure, then spin a separate patch
(and try to remember to keep you on CC..)

...and said patch turns out to conflict with 823066d9edcd, since I
hadn't realised it's already been fixed! So you can go ahead with the
dcache_by_line_op cleanup as well, just rebase onto arm64/for-next/core
(or linux/master, since it's been pulled already).

Thank you very much for the information! I'll rebase with it. 

Robin.

Best Regards,
Kwangwoo Lee