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From:   Qiu Wenbo <qiuwenbo@phytium.com.cn>
To:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        linux-riscv@lists.infradead.org
Cc:     Qiu Wenbo <qiuwenbo@phytium.com.cn>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Atish Patra <atish.patra@wdc.com>,
        Anup Patel <anup@brainfault.org>,
        Guo Ren <guoren@linux.alibaba.com>,
        Zong Li <zong.li@sifive.com>,
        Greentime Hu <greentime.hu@sifive.com>,
        Vincent Chen <vincent.chen@sifive.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH] riscv: Setup exception vector for K210 properly
Date:   Tue, 11 Aug 2020 14:36:56 +0800
Message-Id: <20200811063659.284088-1-qiuwenbo@phytium.com.cn>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Exception vector is missing on nommu platform and it is a big issue.
This patch is tested in Sipeed MAIX Bit Dev Board.

Fixes: 79b1feba5455 ("RISC-V: Setup exception vector early")
Signed-off-by: Qiu Wenbo <qiuwenbo@phytium.com.cn>
---
 arch/riscv/kernel/smpboot.c |  1 +
 arch/riscv/kernel/traps.c   | 11 ++++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 356825a57551..23cde0ceb39d 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -154,6 +154,7 @@ asmlinkage __visible void smp_callin(void)
 	mmgrab(mm);
 	current->active_mm = mm;
 
+	trap_init();
 	notify_cpu_starting(curr_cpuid);
 	update_siblings_masks(curr_cpuid);
 	set_cpu_online(curr_cpuid, 1);
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index ad14f4466d92..a390239818ae 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -174,7 +174,16 @@ int is_valid_bugaddr(unsigned long pc)
 }
 #endif /* CONFIG_GENERIC_BUG */
 
-/* stvec & scratch is already set from head.S */
+/* stvec & scratch is already set from head.S when mmu is enabled */
 void trap_init(void)
 {
+#ifndef CONFIG_MMU
+	/*
+	 * Set sup0 scratch register to 0, indicating to exception vector
+	 * that we are presently executing in the kernel
+	 */
+	csr_write(CSR_SCRATCH, 0);
+	/* Set the exception vector address */
+	csr_write(CSR_TVEC, &handle_exception);
+#endif
 }
-- 
2.28.0