On 02/09/2021 08:11 PM, Thomas Bogendoerfer wrote:
On Tue, Feb 09, 2021 at 01:05:25PM +0800, Tiezhu Yang wrote:
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@xxxxxxxxxxx>
---
v2: add MIPS_DEBUG_DBP definition
arch/mips/include/asm/mipsregs.h | 4 ++++
arch/mips/kernel/genex.S | 4 ++--
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index a0e8ae5..9c8099a 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -1085,6 +1085,10 @@
#define CVMVMCONF_RMMUSIZEM1_S 0
#define CVMVMCONF_RMMUSIZEM1 (_U64CAST_(0xff) << CVMVMCONF_RMMUSIZEM1_S)
+/* Debug register field definitions */
+#define MIPS_DEBUG_DBP_SHIFT 1
+#define MIPS_DEBUG_DBP (_ULCAST_(1) << MIPS_DEBUG_DBP_SHIFT)
+
/*
* Coprocessor 1 (FPU) register names
*/
diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
index bcce32a..743d759 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, MIPS_DEBUG_DBP # Check for SDBBP.
+ beqz k0, ejtag_return
IMHO both implementations are doing the same thing.
When I read the original code, it looks a little confusing
at first glance, the initial aim of this patch is to make the code
more readable and easier to understand.
Thomas.
