[PATCH v2] arm64: mm: convert __dma_* routines to use start, size

On 27/07/16 02:55, kwangwoo.lee at sk.com wrote:
[...]

quoted

quoted

 /*
- *	__dma_clean_range(start, end)
+ *	__dma_clean_area(start, size)
  *	- start   - virtual start address of region
- *	- end     - virtual end address of region
+ *	- size    - size in question
  */
-__dma_clean_range:
-	dcache_line_size x2, x3
-	sub	x3, x2, #1
-	bic	x0, x0, x3
-1:
+__dma_clean_area:
 alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE
-	dc	cvac, x0
+	dcache_by_line_op cvac, sy, x0, x1, x2, x3
 alternative_else
-	dc	civac, x0
+	dcache_by_line_op civac, sy, x0, x1, x2, x3

dcache_by_line_op is a relatively large macro - is there any way we can
still apply the alternative to just the one instruction which needs it,
as opposed to having to patch the entire mostly-identical routine?

I agree with your opinion. Then, how do you think about using CONFIG_* options
like below? I think that alternative_* macros seems to keep the space for
unused instruction. Is it necessary? Please, share your thought about the
space. Thanks!

+__dma_clean_area:
+#if    defined(CONFIG_ARM64_ERRATUM_826319) || \
+       defined(CONFIG_ARM64_ERRATUM_827319) || \
+       defined(CONFIG_ARM64_ERRATUM_824069) || \
+       defined(CONFIG_ARM64_ERRATUM_819472)
+       dcache_by_line_op civac, sy, x0, x1, x2, x3
+#else
+       dcache_by_line_op cvac, sy, x0, x1, x2, x3
+#endif

That's not ideal, because we still only really want to use the
workaround if we detect a CPU which needs it, rather than baking it in
at compile time. I was thinking more along the lines of pushing the
alternative down into dcache_by_line_op, something like the idea below
(compile-tested only, may not actually be viable).

Robin.

-----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