2018-01-18 13:49:25

by Alexey Brodkin

Subject: [PATCH] ARC: Allow disabling of prefetch operations for debugging purposes

Signed-off-by: Alexey Brodkin <[email protected]>
---
arch/arc/Kconfig | 5 +++++
arch/arc/include/asm/processor.h | 11 +++++++++++
arch/arc/lib/memcpy-archs.S | 16 ++++++++++++++++
arch/arc/lib/memset-archs.S | 6 ++++++
4 files changed, 38 insertions(+)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 9d5fd00d9e91..aa5262e8e43f 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -532,6 +532,11 @@ config ARC_DBG_TLB_PARANOIA
bool "Paranoia Checks in Low Level TLB Handlers"
default n

+config ARC_DISABLE_PREFETCH
+ bool "Disable use of prefetch instructions"
+ default n
+ help
+ Suppresses usage of prefetchw and prealloc instructions.
endif

config ARC_UBOOT_SUPPORT
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index 8ee41e988169..01011c0515d4 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -106,6 +106,17 @@ extern unsigned int get_wchan(struct task_struct *p);
*/
#define current_text_addr() ({ __label__ _l; _l: &&_l; })

+#ifdef CONFIG_ARC_DISABLE_PREFETCH
+#define ARCH_HAS_PREFETCH
+#define prefetch(x)
+
+#define ARCH_HAS_PREFETCHW
+#define prefetchw(x)
+
+#define ARCH_HAS_SPINLOCK_PREFETCH
+#define spin_lock_prefetch(x)
+#endif /* CONFIG_ARC_DISABLE_PREFETCH */
+
#endif /* !__ASSEMBLY__ */

/*
diff --git a/arch/arc/lib/memcpy-archs.S b/arch/arc/lib/memcpy-archs.S
index d61044dd8b58..0a29d024be01 100644
--- a/arch/arc/lib/memcpy-archs.S
+++ b/arch/arc/lib/memcpy-archs.S
@@ -41,8 +41,10 @@
#endif

ENTRY_CFI(memcpy)
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetch [r1] ; Prefetch the read location
prefetchw [r0] ; Prefetch the write location
+#endif
mov.f 0, r2
;;; if size is zero
jz.d [blink]
@@ -72,8 +74,10 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy32_64bytes
;; LOOP START
LOADX (r6, r1)
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
PREFETCH_READ (r1)
PREFETCH_WRITE (r3)
+#endif
LOADX (r8, r1)
LOADX (r10, r1)
LOADX (r4, r1)
@@ -117,9 +121,13 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_1
;; LOOP START
ld.ab r6, [r1, 4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetch [r1, 28] ;Prefetch the next read location
+#endif
ld.ab r8, [r1,4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetchw [r3, 32] ;Prefetch the next write location
+#endif

SHIFT_1 (r7, r6, 24)
or r7, r7, r5
@@ -162,9 +170,13 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_2
;; LOOP START
ld.ab r6, [r1, 4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetch [r1, 28] ;Prefetch the next read location
+#endif
ld.ab r8, [r1,4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetchw [r3, 32] ;Prefetch the next write location
+#endif

SHIFT_1 (r7, r6, 16)
or r7, r7, r5
@@ -204,9 +216,13 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_3
;; LOOP START
ld.ab r6, [r1, 4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetch [r1, 28] ;Prefetch the next read location
+#endif
ld.ab r8, [r1,4]
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetchw [r3, 32] ;Prefetch the next write location
+#endif

SHIFT_1 (r7, r6, 8)
or r7, r7, r5
diff --git a/arch/arc/lib/memset-archs.S b/arch/arc/lib/memset-archs.S
index 62ad4bcb841a..343f292d92a0 100644
--- a/arch/arc/lib/memset-archs.S
+++ b/arch/arc/lib/memset-archs.S
@@ -11,7 +11,9 @@
#undef PREALLOC_NOT_AVAIL

ENTRY_CFI(memset)
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetchw [r0] ; Prefetch the write location
+#endif
mov.f 0, r2
;;; if size is zero
jz.d [blink]
@@ -48,11 +50,13 @@ ENTRY_CFI(memset)

lpnz @.Lset64bytes
;; LOOP START
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
#ifdef PREALLOC_NOT_AVAIL
prefetchw [r3, 64] ;Prefetch the next write location
#else
prealloc [r3, 64]
#endif
+#endif /* CONFIG_ARC_DISABLE_PREFETCH */
#ifdef CONFIG_ARC_HAS_LL64
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
@@ -85,7 +89,9 @@ ENTRY_CFI(memset)
lsr.f lp_count, r2, 5 ;Last remaining max 124 bytes
lpnz .Lset32bytes
;; LOOP START
+#ifndef CONFIG_ARC_DISABLE_PREFETCH
prefetchw [r3, 32] ;Prefetch the next write location
+#endif
#ifdef CONFIG_ARC_HAS_LL64
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
--
2.11.0

2018-01-18 18:49:43

by Vineet Gupta

Subject: Re: [PATCH] ARC: Allow disabling of prefetch operations for debugging purposes

On 01/18/2018 05:48 AM, Alexey Brodkin wrote:
> Signed-off-by: Alexey Brodkin <[email protected]>
> ---
> arch/arc/Kconfig | 5 +++++
> arch/arc/include/asm/processor.h | 11 +++++++++++
> arch/arc/lib/memcpy-archs.S | 16 ++++++++++++++++
> arch/arc/lib/memset-archs.S | 6 ++++++
> 4 files changed, 38 insertions(+)
>
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 9d5fd00d9e91..aa5262e8e43f 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -532,6 +532,11 @@ config ARC_DBG_TLB_PARANOIA
> bool "Paranoia Checks in Low Level TLB Handlers"
> default n
>
> +config ARC_DISABLE_PREFETCH
> + bool "Disable use of prefetch instructions"
> + default n
> + help
> + Suppresses usage of prefetchw and prealloc instructions.
> endif
>
> config ARC_UBOOT_SUPPORT
> diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
> index 8ee41e988169..01011c0515d4 100644
> --- a/arch/arc/include/asm/processor.h
> +++ b/arch/arc/include/asm/processor.h
> @@ -106,6 +106,17 @@ extern unsigned int get_wchan(struct task_struct *p);
> */
> #define current_text_addr() ({ __label__ _l; _l: &&_l; })
>
> +#ifdef CONFIG_ARC_DISABLE_PREFETCH
> +#define ARCH_HAS_PREFETCH
> +#define prefetch(x)
> +
> +#define ARCH_HAS_PREFETCHW
> +#define prefetchw(x)
> +
> +#define ARCH_HAS_SPINLOCK_PREFETCH
> +#define spin_lock_prefetch(x)
> +#endif /* CONFIG_ARC_DISABLE_PREFETCH */
> +
> #endif /* !__ASSEMBLY__ */
>
> /*
> diff --git a/arch/arc/lib/memcpy-archs.S b/arch/arc/lib/memcpy-archs.S
> index d61044dd8b58..0a29d024be01 100644
> --- a/arch/arc/lib/memcpy-archs.S
> +++ b/arch/arc/lib/memcpy-archs.S
> @@ -41,8 +41,10 @@
> #endif
>
> ENTRY_CFI(memcpy)
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetch [r1] ; Prefetch the read location
> prefetchw [r0] ; Prefetch the write location
> +#endif

This code is already unreadable and this change is not helping. Can we make some
macros "C" / gas style and have the switch inside the macro rather than littering
this all over the place please !

> mov.f 0, r2
> ;;; if size is zero
> jz.d [blink]
> @@ -72,8 +74,10 @@ ENTRY_CFI(memcpy)
> lpnz @.Lcopy32_64bytes
> ;; LOOP START
> LOADX (r6, r1)
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> PREFETCH_READ (r1)
> PREFETCH_WRITE (r3)
> +#endif
> LOADX (r8, r1)
> LOADX (r10, r1)
> LOADX (r4, r1)
> @@ -117,9 +121,13 @@ ENTRY_CFI(memcpy)
> lpnz @.Lcopy8bytes_1
> ;; LOOP START
> ld.ab r6, [r1, 4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetch [r1, 28] ;Prefetch the next read location
> +#endif
> ld.ab r8, [r1,4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetchw [r3, 32] ;Prefetch the next write location
> +#endif
>
> SHIFT_1 (r7, r6, 24)
> or r7, r7, r5
> @@ -162,9 +170,13 @@ ENTRY_CFI(memcpy)
> lpnz @.Lcopy8bytes_2
> ;; LOOP START
> ld.ab r6, [r1, 4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetch [r1, 28] ;Prefetch the next read location
> +#endif
> ld.ab r8, [r1,4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetchw [r3, 32] ;Prefetch the next write location
> +#endif
>
> SHIFT_1 (r7, r6, 16)
> or r7, r7, r5
> @@ -204,9 +216,13 @@ ENTRY_CFI(memcpy)
> lpnz @.Lcopy8bytes_3
> ;; LOOP START
> ld.ab r6, [r1, 4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetch [r1, 28] ;Prefetch the next read location
> +#endif
> ld.ab r8, [r1,4]
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetchw [r3, 32] ;Prefetch the next write location
> +#endif
>
> SHIFT_1 (r7, r6, 8)
> or r7, r7, r5
> diff --git a/arch/arc/lib/memset-archs.S b/arch/arc/lib/memset-archs.S
> index 62ad4bcb841a..343f292d92a0 100644
> --- a/arch/arc/lib/memset-archs.S
> +++ b/arch/arc/lib/memset-archs.S
> @@ -11,7 +11,9 @@
> #undef PREALLOC_NOT_AVAIL
>
> ENTRY_CFI(memset)
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetchw [r0] ; Prefetch the write location
> +#endif
> mov.f 0, r2
> ;;; if size is zero
> jz.d [blink]
> @@ -48,11 +50,13 @@ ENTRY_CFI(memset)
>
> lpnz @.Lset64bytes
> ;; LOOP START
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> #ifdef PREALLOC_NOT_AVAIL
> prefetchw [r3, 64] ;Prefetch the next write location
> #else
> prealloc [r3, 64]
> #endif
> +#endif /* CONFIG_ARC_DISABLE_PREFETCH */
> #ifdef CONFIG_ARC_HAS_LL64
> std.ab r4, [r3, 8]
> std.ab r4, [r3, 8]
> @@ -85,7 +89,9 @@ ENTRY_CFI(memset)
> lsr.f lp_count, r2, 5 ;Last remaining max 124 bytes
> lpnz .Lset32bytes
> ;; LOOP START
> +#ifndef CONFIG_ARC_DISABLE_PREFETCH
> prefetchw [r3, 32] ;Prefetch the next write location
> +#endif
> #ifdef CONFIG_ARC_HAS_LL64
> std.ab r4, [r3, 8]
> std.ab r4, [r3, 8]