riscv: Setup exception vector for nommu platform

Exception vector is missing on nommu platform and that is an issue.
This patch is tested in Sipeed Maix Bit Dev Board.

Fixes: 00f8bde9e489 ("RISC-V: Setup exception vector early")
Suggested-by: Anup Patel <anup@brainfault.org>
Suggested-by: Atish Patra <atishp@atishpatra.org>
Signed-off-by: Qiu Wenbo <qiuwenbo@phytium.com.cn>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index d0c5c316e9bb12090fbbd9a8f39dcfc8b6d81b6a..0a4e81b8dc7957dc86dc0ee218493bf6a014cdf2 100644 (file)
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -77,16 +77,10 @@ relocate:
        csrw CSR_SATP, a0
 .align 2
 1:
-       /* Set trap vector to exception handler */
-       la a0, handle_exception
+       /* Set trap vector to spin forever to help debug */
+       la a0, .Lsecondary_park
        csrw CSR_TVEC, a0
 
-       /*
-        * Set sup0 scratch register to 0, indicating to exception vector that
-        * we are presently executing in kernel.
-        */
-       csrw CSR_SCRATCH, zero
-
        /* Reload the global pointer */
 .option push
 .option norelax
@@ -144,9 +138,23 @@ secondary_start_common:
        la a0, swapper_pg_dir
        call relocate
 #endif
+       call setup_trap_vector
        tail smp_callin
 #endif /* CONFIG_SMP */
 
+.align 2
+setup_trap_vector:
+       /* Set trap vector to exception handler */
+       la a0, handle_exception
+       csrw CSR_TVEC, a0
+
+       /*
+        * Set sup0 scratch register to 0, indicating to exception vector that
+        * we are presently executing in kernel.
+        */
+       csrw CSR_SCRATCH, zero
+       ret
+
 .Lsecondary_park:
        /* We lack SMP support or have too many harts, so park this hart */
        wfi
@@ -240,6 +248,7 @@ clear_bss_done:
        call relocate
 #endif /* CONFIG_MMU */
 
+       call setup_trap_vector
        /* Restore C environment */
        la tp, init_task
        sw zero, TASK_TI_CPU(tp)