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Add "better" MIPS24k and MIPS74k barriers.

* the mips74k cores only need EHB (which is 'sll $0, $0, 3')
  here; NOPs don't actually work.

* add EHB as the last NOP for the default barriers/hazards;
  that is "better" behaviour and should work on a wider
  variety of processors.

This allows the existing (icky) TLB code to work, allowing
the AR9344 SoC (mips74k) to actually get through kernel startup.


* AR9344 SoC - (mips74k)
* AR9331 SoC - (mips24k)


* test on mips4k CPUs, just to be sure.

* document that sll $0, $0, 3 is actually "EHB" and that it
  falls back to being a NOP for pre-mips32r1.

* mips24k has an errata that we currently don't correctly explicitly
  state - ie, that after DERET/ERET, the only valid instruction is
  a NOP.

Reviewed by:	imp@
Approved by:	re@ (gjb)
  • Loading branch information...
commit 2d83a106ef6be8c710efe1d9b7af3cd23e360ce6 1 parent ce0fc24
adrian authored
Showing with 13 additions and 3 deletions.
  1. +5 −2 sys/mips/include/asm.h
  2. +8 −1 sys/mips/include/cpuregs.h
7 sys/mips/include/asm.h
@@ -725,9 +725,12 @@ _C_LABEL(x):
#elif defined(CPU_RMI)
+#elif defined(CPU_MIPS74KC)
+#define HAZARD_DELAY sll $0,$0,3
+#define ITLBNOPFIX sll $0,$0,3
-#define ITLBNOPFIX nop;nop;nop;nop;nop;nop;nop;nop;nop;nop;
-#define HAZARD_DELAY nop;nop;nop;nop;nop;
+#define ITLBNOPFIX nop;nop;nop;nop;nop;nop;nop;nop;nop;sll $0,$0,3;
+#define HAZARD_DELAY nop;nop;nop;nop;sll $0,$0,3;
#endif /* !_MACHINE_ASM_H_ */
9 sys/mips/include/cpuregs.h
@@ -149,6 +149,11 @@
#define MIPS_CCA_CC 0x05 /* Cacheable Coherent. */
+#if defined(CPU_MIPS74KC)
+#define MIPS_CCA_UNCACHED 0x02
+#define MIPS_CCA_CACHED 0x00
@@ -204,12 +209,14 @@
#define COP0_SYNC .word 0xc0 /* ehb */
#elif defined(CPU_SB1)
#define COP0_SYNC ssnop; ssnop; ssnop; ssnop; ssnop; ssnop; ssnop; ssnop; ssnop
+#elif defined(CPU_MIPS74KC)
+#define COP0_SYNC .word 0xc0 /* ehb */
* Pick a reasonable default based on the "typical" spacing described in the
* "CP0 Hazards" chapter of MIPS Architecture Book Vol III.
-#define COP0_SYNC ssnop; ssnop; ssnop; ssnop; ssnop
+#define COP0_SYNC ssnop; ssnop; ssnop; ssnop; .word 0xc0;
#define COP0_HAZARD_FPUENABLE nop; nop; nop; nop;
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