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authorSteven J. Hill <Steven.Hill@imgtec.com>2013-03-25 12:15:55 -0500
committerRalf Baechle <ralf@linux-mips.org>2013-05-09 17:55:18 +0200
commit2a0b24f56c2492b932f1aed617ae80fb23500d21 (patch)
treec9aec2872f912c65b83a92a66fe94f6006427d73 /arch/mips/mti-sead3
parent102cedc32a6e3cd537374a3678d407591d5a6fab (diff)
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>
Diffstat (limited to 'arch/mips/mti-sead3')
-rw-r--r--arch/mips/mti-sead3/sead3-init.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/arch/mips/mti-sead3/sead3-init.c b/arch/mips/mti-sead3/sead3-init.c
index 562dccf56ee8..bfbd17b120a2 100644
--- a/arch/mips/mti-sead3/sead3-init.c
+++ b/arch/mips/mti-sead3/sead3-init.c
@@ -65,7 +65,41 @@ static void __init mips_nmi_setup(void)
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 @@ static void __init mips_ejtag_setup(void)
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);
}