linux-kernel - [PATCH] MIPS: Make check condition for SDBBP consistent with EJTAG spec

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Message-Id: <1612790085-14436-1-git-send-email-yangtiezhu@loongson.cn>
Date:   Mon,  8 Feb 2021 21:14:45 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: [PATCH] MIPS: Make check condition for SDBBP consistent with EJTAG spec

According to MIPS EJTAG Specification [1], a Debug Breakpoint
exception occurs when an SDBBP instruction is executed, the
CP0_DEBUG bit DBp indicates that a Debug Breakpoint exception
occurred, just check bit DBp for SDBBP is more accurate.

[1] http://www.t-es-t.hu/download/mips/md00047f.pdf

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 arch/mips/kernel/genex.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index bcce32a..6336826 100644
--- a/arch/mips/kernel/genex.S
+++ b/arch/mips/kernel/genex.S
@@ -349,8 +349,8 @@ NESTED(ejtag_debug_handler, PT_SIZE, sp)
 	MTC0	k0, CP0_DESAVE
 	mfc0	k0, CP0_DEBUG
 
-	sll	k0, k0, 30	# Check for SDBBP.
-	bgez	k0, ejtag_return
+	andi	k0, k0, 0x2	# Check for SDBBP.
+	beqz	k0, ejtag_return
 
 #ifdef CONFIG_SMP
 1:	PTR_LA	k0, ejtag_debug_buffer_spinlock
-- 
2.1.0