linux-kernel - [PATCH 3.16 282/306] parisc: Remove unnecessary TLB purges from flush_dcache_page_asm and flush_icache_page

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Message-ID: <lsq.1487198501.35859410@decadent.org.uk>
Date:   Wed, 15 Feb 2017 22:41:41 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "John David Anglin" <dave.anglin@...l.net>,
        "Helge Deller" <deller@....de>
Subject: [PATCH 3.16 282/306] parisc: Remove unnecessary TLB purges from
 flush_dcache_page_asm and flush_icache_page_asm

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: John David Anglin <dave.anglin@...l.net>

commit febe42964fe182281859b3d43d844bb25ca49367 upstream.

We have four routines in pacache.S that use temporary alias pages:
copy_user_page_asm(), clear_user_page_asm(), flush_dcache_page_asm() and
flush_icache_page_asm().  copy_user_page_asm() and clear_user_page_asm()
don't purge the TLB entry used for the operation.
flush_dcache_page_asm() and flush_icache_page_asm do purge the entry.

Presumably, this was thought to optimize TLB use.  However, the
operation is quite heavy weight on PA 1.X processors as we need to take
the TLB lock and a TLB broadcast is sent to all processors.

This patch removes the purges from flush_dcache_page_asm() and
flush_icache_page_asm.

Signed-off-by: John David Anglin  <dave.anglin@...l.net>
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/parisc/kernel/pacache.S | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

--- a/arch/parisc/kernel/pacache.S
+++ b/arch/parisc/kernel/pacache.S
@@ -886,19 +886,10 @@ ENTRY(flush_dcache_page_asm)
 	fdc,m		r31(%r28)
 	fdc,m		r31(%r28)
 	fdc,m		r31(%r28)
-	cmpb,COND(<<)		%r28, %r25,1b
+	cmpb,COND(<<)	%r28, %r25,1b
 	fdc,m		r31(%r28)

 	sync
-
-#ifdef CONFIG_PA20
-	pdtlb,l		%r0(%r25)
-#else
-	tlb_lock	%r20,%r21,%r22
-	pdtlb		%r0(%r25)
-	tlb_unlock	%r20,%r21,%r22
-#endif
-
 	bv		%r0(%r2)
 	nop
 	.exit
@@ -973,17 +964,6 @@ ENTRY(flush_icache_page_asm)
 	fic,m		%r31(%sr4,%r28)

 	sync
-
-#ifdef CONFIG_PA20
-	pdtlb,l		%r0(%r28)
-	pitlb,l         %r0(%sr4,%r25)
-#else
-	tlb_lock        %r20,%r21,%r22
-	pdtlb		%r0(%r28)
-	pitlb           %r0(%sr4,%r25)
-	tlb_unlock      %r20,%r21,%r22
-#endif
-
 	bv		%r0(%r2)
 	nop
 	.exit