[RFC] MIPS: R5900: The ERET instruction has issues with delay slot and CACHE

[Fredrik Noring <noring@nocrew.org>]

Signed-off-by: Fredrik Noring <noring@nocrew.org>
---
This change has been ported from v2.6 patches. I have not found any note
describing this in the TX79 manual.

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index e23765312e25..b67f31d04716 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1378,6 +1378,16 @@ static void build_r4000_tlb_refill_handler(void)
 		uasm_l_leave(&l, p);
 		uasm_i_eret(&p); /* return from trap */
 	}
+
+#ifdef CONFIG_CPU_R5900
+	/* There should be nothing which can be interpreted as cache instruction. */
+	uasm_i_nop(&p);
+	uasm_i_nop(&p);
+	uasm_i_nop(&p);
+	uasm_i_nop(&p);
+	uasm_i_nop(&p);
+#endif
+
 #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
 	uasm_l_tlb_huge_update(&l, p);
 	if (htlb_info.need_reload_pte)
@@ -2132,6 +2142,14 @@ build_r4000_tlbchange_handler_tail(u32 **p, struct uasm_label **l,
 	uasm_l_leave(l, *p);
 	build_restore_work_registers(p);
 	uasm_i_eret(p); /* return from trap */
+#ifdef CONFIG_CPU_R5900
+	/* There should be nothing which can be interpreted as cache instruction. */
+	uasm_i_nop(p);
+	uasm_i_nop(p);
+	uasm_i_nop(p);
+	uasm_i_nop(p);
+	uasm_i_nop(p);
+#endif
 
 #ifdef CONFIG_64BIT
 	build_get_pgd_vmalloc64(p, l, r, tmp, ptr, not_refill);