> -----Original Message-----
> From: Robin Murphy [mailto:robin.mur...@arm.com]
> Sent: Wednesday, July 27, 2016 6:56 PM
> To: 이광우(LEE KWANGWOO) MS SW; Russell King - ARM Linux; Catalin Marinas; Will
> Deacon; Mark Rutland;
> linux-arm-ker...@lists.infradead.org
> Cc: 김현철(KIM HYUNCHUL) MS SW; linux-kernel@vger.kernel.org; 정우석(CHUNG WOO SUK)
> MS SW
> Subject: Re: [PATCH v2] arm64: mm: convert __dma_* routines to use start, size
>
> On 27/07/16 02:55, kwangwoo....@sk.com wrote:
> [...]
> >>> /*
> >>> - * __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).
OK. Using the capability of CPU features seems to be preferred.
> 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
I agree that it looks not viable because it makes the macro bigger and
conditional specifically with CVAC op.
Then.. if the number of the usage of alternative_* macros for erratum is
few (just one in this case for cache clean), I think only small change like
below seems to be optimal and there is no need to create a variant macro of
dcache_cache_by_line_op. How do you think about it?
/*
- * __dma_clean_range(start, end)
+ * __clean_dcache_area_poc(kaddr, size)
+ *
+ * Ensure that any D-cache lines for the interval [kaddr, kaddr+size)
+ * are cleaned to the PoC.
+ *
+ * - kaddr - kernel address
+ * - size - size in question
+ */
+ENTRY(__clean_dcache_area_poc)
+ /* FALLTHROUGH */
+
+/*
+ * __dma_clean_area(start, size)
* - start - virtual start address of region
- * - end - virtual end address of region
+ * - size - size in question
*/
-__dma_clean_range:
+__dma_clean_area:
+ add x1, x1, x0
dcache_line_size x2, x3
sub x3, x2, #1
bic x0, x0, x3
@@ -158,24 +172,21 @@ alternative_endif
b.lo 1b
dsb sy
ret
-ENDPROC(__dma_clean_range)
+ENDPIPROC(__clean_dcache_area_poc)
+ENDPROC(__dma_clean_area)
Regards,
Kwangwoo Lee
