linux-kernel - [PATCH v2 34/36] MIPS: genex: Add Loongson3 LL/SC workaround to ejtag_debug

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Date:   Tue, 1 Oct 2019 21:53:42 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
CC:     Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Paul Burton <pburton@...ecomp.com>
Subject: [PATCH v2 34/36] MIPS: genex: Add Loongson3 LL/SC workaround to
 ejtag_debug_handler

In ejtag_debug_handler we use LL & SC instructions to acquire & release
an open-coded spinlock. For Loongson3 systems affected by LL/SC errata
this requires that we insert a sync instruction prior to the LL in order
to ensure correct behavior of the LL/SC loop.

Signed-off-by: Paul Burton <paul.burton@...s.com>
---

Changes in v2: None

 arch/mips/kernel/genex.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index efde27c99414..ac4f2b835165 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -18,6 +18,7 @@
 #include <asm/fpregdef.h>
 #include <asm/mipsregs.h>
 #include <asm/stackframe.h>
+#include <asm/sync.h>
 #include <asm/war.h>
 #include <asm/thread_info.h>
 
@@ -353,6 +354,7 @@ NESTED(ejtag_debug_handler, PT_SIZE, sp)
 
 #ifdef CONFIG_SMP
 1:	PTR_LA	k0, ejtag_debug_buffer_spinlock
+	__SYNC(full, loongson3_war)
 	ll	k0, 0(k0)
 	bnez	k0, 1b
 	PTR_LA	k0, ejtag_debug_buffer_spinlock
-- 
2.23.0