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[PATCH v2 20/25] powerpc32: Remove clear_pages() and define clear_page() inline

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  [PATCH v2 20/25] powerpc32: Remove clear_pages() and define  clear_page() inline Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-22 19:00 +0200
    Re: [PATCH v2 20/25] powerpc32: Remove clear_pages() and define  clear_page() inline Joakim Tjernlund <joakim.tjernlund@transmode.se> - 2015-09-22 20:00 +0200
    Re: [PATCH v2 20/25] powerpc32: Remove clear_pages() and define  clear_page() inline Scott Wood <scottwood@freescale.com> - 2015-09-29 02:30 +0200

#1230483 — [PATCH v2 20/25] powerpc32: Remove clear_pages() and define clear_page() inline

clear_pages() is never used, and PPC32 is the only architecture
(still) having this function. Neither PPC64 nor any other
architecture has it.

This patch removes clear_page() and move clear_page() function
inline (same as PPC64) as it only is a few isns

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
No change in v2

 arch/powerpc/include/asm/page_32.h | 17 ++++++++++++++---
 arch/powerpc/kernel/misc_32.S      | 16 ----------------
 arch/powerpc/kernel/ppc_ksyms_32.c |  1 -
 3 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/include/asm/page_32.h b/arch/powerpc/include/asm/page_32.h
index 68d73b2..6a8e179 100644
--- a/arch/powerpc/include/asm/page_32.h
+++ b/arch/powerpc/include/asm/page_32.h
@@ -1,6 +1,8 @@
 #ifndef _ASM_POWERPC_PAGE_32_H
 #define _ASM_POWERPC_PAGE_32_H
 
+#include <asm/cache.h>
+
 #if defined(CONFIG_PHYSICAL_ALIGN) && (CONFIG_PHYSICAL_START != 0)
 #if (CONFIG_PHYSICAL_START % CONFIG_PHYSICAL_ALIGN) != 0
 #error "CONFIG_PHYSICAL_START must be a multiple of CONFIG_PHYSICAL_ALIGN"
@@ -36,9 +38,18 @@ typedef unsigned long long pte_basic_t;
 typedef unsigned long pte_basic_t;
 #endif
 
-struct page;
-extern void clear_pages(void *page, int order);
-static inline void clear_page(void *page) { clear_pages(page, 0); }
+/*
+ * Clear page using the dcbz instruction, which doesn't cause any
+ * memory traffic (except to write out any cache lines which get
+ * displaced).  This only works on cacheable memory.
+ */
+static inline void clear_page(void *addr)
+{
+	unsigned int i;
+
+	for (i = 0; i < PAGE_SIZE / L1_CACHE_BYTES; i++, addr += L1_CACHE_BYTES)
+		dcbz(addr);
+}
 extern void copy_page(void *to, void *from);
 
 #include <asm-generic/getorder.h>
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index 72fd7a7..ce3ca08 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -517,22 +517,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
 #endif /* CONFIG_BOOKE */
 
 /*
- * Clear pages using the dcbz instruction, which doesn't cause any
- * memory traffic (except to write out any cache lines which get
- * displaced).  This only works on cacheable memory.
- *
- * void clear_pages(void *page, int order) ;
- */
-_GLOBAL(clear_pages)
-	li	r0,PAGE_SIZE/L1_CACHE_BYTES
-	slw	r0,r0,r4
-	mtctr	r0
-1:	dcbz	0,r3
-	addi	r3,r3,L1_CACHE_BYTES
-	bdnz	1b
-	blr
-
-/*
  * Copy a whole page.  We use the dcbz instruction on the destination
  * to reduce memory traffic (it eliminates the unnecessary reads of
  * the destination into cache).  This requires that the destination
diff --git a/arch/powerpc/kernel/ppc_ksyms_32.c b/arch/powerpc/kernel/ppc_ksyms_32.c
index 30ddd8a..2bfaafe 100644
--- a/arch/powerpc/kernel/ppc_ksyms_32.c
+++ b/arch/powerpc/kernel/ppc_ksyms_32.c
@@ -10,7 +10,6 @@
 #include <asm/pgtable.h>
 #include <asm/dcr.h>
 
-EXPORT_SYMBOL(clear_pages);
 EXPORT_SYMBOL(ISA_DMA_THRESHOLD);
 EXPORT_SYMBOL(DMA_MODE_READ);
 EXPORT_SYMBOL(DMA_MODE_WRITE);
-- 
2.1.0

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#1230572

Hi Christophe

Really nice patchset!

On Tue, 2015-09-22 at 18:51 +0200, Christophe Leroy wrote:
> clear_pages() is never used, and PPC32 is the only architecture
> (still) having this function. Neither PPC64 nor any other
> architecture has it.
> 
> This patch removes clear_page() and move clear_page() function
> inline (same as PPC64) as it only is a few isns
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> No change in v2
> 
>  arch/powerpc/include/asm/page_32.h | 17 ++++++++++++++---
>  arch/powerpc/kernel/misc_32.S      | 16 ----------------
>  arch/powerpc/kernel/ppc_ksyms_32.c |  1 -
>  3 files changed, 14 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/page_32.h b/arch/powerpc/include/asm/page_32.h
> index 68d73b2..6a8e179 100644
> --- a/arch/powerpc/include/asm/page_32.h
> +++ b/arch/powerpc/include/asm/page_32.h
> @@ -1,6 +1,8 @@
>  #ifndef _ASM_POWERPC_PAGE_32_H
>  #define _ASM_POWERPC_PAGE_32_H
>  
> +#include <asm/cache.h>
> +
>  #if defined(CONFIG_PHYSICAL_ALIGN) && (CONFIG_PHYSICAL_START != 0)
>  #if (CONFIG_PHYSICAL_START % CONFIG_PHYSICAL_ALIGN) != 0
>  #error "CONFIG_PHYSICAL_START must be a multiple of CONFIG_PHYSICAL_ALIGN"
> @@ -36,9 +38,18 @@ typedef unsigned long long pte_basic_t;
>  typedef unsigned long pte_basic_t;
>  #endif
>  
> -struct page;
> -extern void clear_pages(void *page, int order);
> -static inline void clear_page(void *page) { clear_pages(page, 0); }
> +/*
> + * Clear page using the dcbz instruction, which doesn't cause any
> + * memory traffic (except to write out any cache lines which get
> + * displaced).  This only works on cacheable memory.
> + */
> +static inline void clear_page(void *addr)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < PAGE_SIZE / L1_CACHE_BYTES; i++, addr += L1_CACHE_BYTES)
> +		dcbz(addr);
> +}

Does gcc manage to transform this into efficient asm?
Otherwise you could help gcc by using do { .. } while(--i); instead.
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#1234593

On Tue, Sep 22, 2015 at 06:51:09PM +0200, Christophe Leroy wrote:
> clear_pages() is never used, and PPC32 is the only architecture
> (still) having this function. Neither PPC64 nor any other
> architecture has it.

It is used, by clear_page().

> This patch removes clear_page() and move clear_page() function
> inline (same as PPC64) as it only is a few isns

It removes clear_pages(), not clear_page().

-Scott
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