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@imgtec.com
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Changes in v2: - Rebase atop u-boot-mips/next - Execute a wait instruction in the loop - Fill delay slots with NOPs
arch/mips/cpu/start.S | 31 ++++++++++++++++++++++++++++++- arch/mips/include/asm/mipsregs.h | 7 +++++++ 2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/arch/mips/cpu/start.S b/arch/mips/cpu/start.S index 8f85ede..171fbfd 100644 --- a/arch/mips/cpu/start.S +++ b/arch/mips/cpu/start.S @@ -108,9 +108,38 @@ 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 */ + beqz t0, 1f + nop +2: wait + b 2b + nop
/* Clear watch registers */ - MTC0 zero, CP0_WATCHLO +1: MTC0 zero, CP0_WATCHLO mtc0 zero, CP0_WATCHHI
/* WP(Watch Pending), SW0/1 should be cleared */ diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h index b4c2dff..9ab5063 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. */ @@ -553,6 +559,7 @@ #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_L2C (_ULCAST_(1) << 10)