[U-Boot] [PATCH] MIPS: Hang if run on a secondary CPU

[Paul Burton]

Some systems are configured such that multiple CPUs begin running from
their reset vector following a system reset. If this occurs then U-Boot
will be run on multiple CPUs simultaneously, which causes all sorts of
issues as the multiple instances of U-Boot clobber each other.

Prevent this from happening by simply hanging with an infinite loop if
we run on a CPU whose ID, as determined by GlobalNumber or EBase.CPUNum
as appropriate, is non-zero.

Signed-off-by: Paul Burton <paul.burton at imgtec.com>
---

 arch/mips/cpu/start.S            | 25 +++++++++++++++++++++++++
 arch/mips/include/asm/mipsregs.h |  7 +++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/mips/cpu/start.S b/arch/mips/cpu/start.S
index fc6dd66..dd37ac3 100644
--- a/arch/mips/cpu/start.S
+++ b/arch/mips/cpu/start.S
@@ -112,6 +112,31 @@ ENTRY(_start)
 
 	.align 4
 reset:
+#if __mips_isa_rev >= 6
+	.set	push
+	.set	reorder
+	mfc0	t0, CP0_CONFIG, 1
+	bgez	t0, 1f
+	mfc0	t0, CP0_CONFIG, 2
+	bgez	t0, 1f
+	mfc0	t0, CP0_CONFIG, 3
+	bgez	t0, 1f
+	mfc0	t0, CP0_CONFIG, 4
+	bgez	t0, 1f
+	mfc0	t0, CP0_CONFIG, 5
+	and	t0, t0, MIPS_CONF5_VP
+	beqz	t0, 1f
+
+	mfc0	t0, CP0_GLOBALNUMBER
+	b	2f
+	.set	pop
+#endif
+
+1:	mfc0	t0, CP0_EBASE
+	and	t0, t0, EBASE_CPUNUM
+
+	/* Hang if this isn't the first CPU in the system */
+2:	bnez	t0, .
 
 	/* Clear watch registers */
 	MTC0	zero, CP0_WATCHLO
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 3185dc7..9a4c4c5 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -39,6 +39,7 @@
 #define CP0_ENTRYLO0 $2
 #define CP0_ENTRYLO1 $3
 #define CP0_CONF $3
+#define CP0_GLOBALNUMBER $3, 1
 #define CP0_CONTEXT $4
 #define CP0_PAGEMASK $5
 #define CP0_WIRED $6
@@ -361,6 +362,11 @@
 #define CAUSEF_BD		(_ULCAST_(1)   << 31)
 
 /*
+ * Bits in the coprocessor 0 EBase register.
+ */
+#define EBASE_CPUNUM		0x3ff
+
+/*
  * Bits in the coprocessor 0 config register.
  */
 /* Generic bits.  */
@@ -548,6 +554,7 @@
 #define MIPS_CONF5_MRP		(_ULCAST_(1) << 3)
 #define MIPS_CONF5_LLB		(_ULCAST_(1) << 4)
 #define MIPS_CONF5_MVH		(_ULCAST_(1) << 5)
+#define MIPS_CONF5_VP		(_ULCAST_(1) << 7)
 #define MIPS_CONF5_FRE		(_ULCAST_(1) << 8)
 #define MIPS_CONF5_UFE		(_ULCAST_(1) << 9)
 #define MIPS_CONF5_MSAEN	(_ULCAST_(1) << 27)
-- 
2.10.0