MIPS: microMIPS: Add support for exception handling.
All exceptions must be taken in microMIPS mode, never in classic
MIPS mode or the kernel falls apart. A few NOP instructions are
used to maintain the correct alignment of microMIPS versions of
the exception vectors.
Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
diff --git a/arch/mips/mti-sead3/sead3-init.c b/arch/mips/mti-sead3/sead3-init.c
index 562dccf..bfbd17b 100644
--- a/arch/mips/mti-sead3/sead3-init.c
+++ b/arch/mips/mti-sead3/sead3-init.c
@@ -65,7 +65,41 @@
base = cpu_has_veic ?
(void *)(CAC_BASE + 0xa80) :
(void *)(CAC_BASE + 0x380);
+#ifdef CONFIG_CPU_MICROMIPS
+ /*
+ * Decrement the exception vector address by one for microMIPS.
+ */
+ memcpy(base, (&except_vec_nmi - 1), 0x80);
+
+ /*
+ * This is a hack. We do not know if the boot loader was built with
+ * microMIPS instructions or not. If it was not, the NMI exception
+ * code at 0x80000a80 will be taken in MIPS32 mode. The hand coded
+ * assembly below forces us into microMIPS mode if we are a pure
+ * microMIPS kernel. The assembly instructions are:
+ *
+ * 3C1A8000 lui k0,0x8000
+ * 375A0381 ori k0,k0,0x381
+ * 03400008 jr k0
+ * 00000000 nop
+ *
+ * The mode switch occurs by jumping to the unaligned exception
+ * vector address at 0x80000381 which would have been 0x80000380
+ * in MIPS32 mode. The jump to the unaligned address transitions
+ * us into microMIPS mode.
+ */
+ if (!cpu_has_veic) {
+ void *base2 = (void *)(CAC_BASE + 0xa80);
+ *((unsigned int *)base2) = 0x3c1a8000;
+ *((unsigned int *)base2 + 1) = 0x375a0381;
+ *((unsigned int *)base2 + 2) = 0x03400008;
+ *((unsigned int *)base2 + 3) = 0x00000000;
+ flush_icache_range((unsigned long)base2,
+ (unsigned long)base2 + 0x10);
+ }
+#else
memcpy(base, &except_vec_nmi, 0x80);
+#endif
flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
}
@@ -76,7 +110,21 @@
base = cpu_has_veic ?
(void *)(CAC_BASE + 0xa00) :
(void *)(CAC_BASE + 0x300);
+#ifdef CONFIG_CPU_MICROMIPS
+ /* Deja vu... */
+ memcpy(base, (&except_vec_ejtag_debug - 1), 0x80);
+ if (!cpu_has_veic) {
+ void *base2 = (void *)(CAC_BASE + 0xa00);
+ *((unsigned int *)base2) = 0x3c1a8000;
+ *((unsigned int *)base2 + 1) = 0x375a0301;
+ *((unsigned int *)base2 + 2) = 0x03400008;
+ *((unsigned int *)base2 + 3) = 0x00000000;
+ flush_icache_range((unsigned long)base2,
+ (unsigned long)base2 + 0x10);
+ }
+#else
memcpy(base, &except_vec_ejtag_debug, 0x80);
+#endif
flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
}