linux-kernel - [PATCH 2/2] nds32: Fill all TLB entries with kernel image mapping

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Message-Id: <480e740a44661c04316044ed23982c730986c840.1539781832.git.zongbox@gmail.com>
Date:   Wed, 17 Oct 2018 21:15:52 +0800
From:   Zong Li <zongbox@...il.com>
To:     green.hu@...il.com, deanbo422@...il.com,
        linux-kernel@...r.kernel.org
Cc:     greentime@...estech.com, Zong Li <zongbox@...il.com>,
        Zong Li <zong@...estech.com>
Subject: [PATCH 2/2] nds32: Fill all TLB entries with kernel image mapping

We use earlycon replace with early_printk and doesn't use
early_io_map() to create UART mapping. It is not necessary
to reserve the one way in TLB for now.

It didn't make sense if use direct-mapped and reserve one
way at the same time. It allow the direct-mapped now.

Signed-off-by: Zong Li <zong@...estech.com>
---
 arch/nds32/kernel/head.S | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/nds32/kernel/head.S b/arch/nds32/kernel/head.S
index 1ce653d..2c8aac6 100644
--- a/arch/nds32/kernel/head.S
+++ b/arch/nds32/kernel/head.S
@@ -123,14 +123,7 @@ _image_size_check:
         andi    $r0, $r0, MMU_CFG_mskTBS
         srli    $r6, $r6, MMU_CFG_offTBW
         srli    $r0, $r0, MMU_CFG_offTBS
-        /*
-         * we just map the kernel to the maximum way - 1 of tlb
-         * reserver one way for UART VA mapping
-         * it will cause page fault if UART mapping cover the kernel mapping
-         *
-         * direct mapping is not supported now.
-         */
-        beqz    $r6, __error                 ! MMU_CFG.TBW = 0 is direct mappin
+	addi    $r6, $r6, #0x1               ! MMU_CFG.TBW value -> meaning
         addi    $r0, $r0, #0x2               ! MMU_CFG.TBS value -> meaning
         sll     $r0, $r6, $r0                ! entries = k-way * n-set
         mul     $r6, $r0, $r5                ! max size = entries * page size
-- 
2.7.4