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Re: [PATCH 3/4] MIPS: deal with larger physical offset

To: Florian Fainelli <florian@openwrt.org>
Subject: Re: [PATCH 3/4] MIPS: deal with larger physical offset
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 04 Jan 2010 09:54:48 -0800
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <201001032117.26581.florian@openwrt.org>
References: <201001032117.26581.florian@openwrt.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.21 (X11/20090320)
Florian Fainelli wrote:
AR7 has a larger physical offset than other MIPS based
systems and therefore needs to setup handlers differently.
This version uses uasm instead of the hand crafted assembly
previously sent. This modification is also required for
running the kernel in mapped address space.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Eugene Konev <ejka@imfi.kspu.ru>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
---
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 308e434..dbf52ab 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -51,6 +51,8 @@
 #include <asm/stacktrace.h>
 #include <asm/irq.h>
+#include "../mm/uasm.h"
+


The first time this came up, it was suggested that uasm.h move to asm/uasm.h so that we don't have this ugliness. I think it is still a good idea.

 extern void check_wait(void);
 extern asmlinkage void r4k_wait(void);
 extern asmlinkage void rollback_handle_int(void);
@@ -1283,9 +1285,18 @@ void *set_except_vector(int n, void *addr)
exception_handlers[n] = handler;
        if (n == 0 && cpu_has_divec) {
-               *(u32 *)(ebase + 0x200) = 0x08000000 |
-                                         (0x03ffffff & (handler >> 2));
-               local_flush_icache_range(ebase + 0x200, ebase + 0x204);
+               unsigned long jump_mask = ~((1 << 28) - 1);
+               u32 *buf = (u32 *)(ebase + 0x200);
+               unsigned int k0 = 26;
+               if((handler & jump_mask) == ((ebase + 0x200) & jump_mask)) {
+                       uasm_i_j(&buf, handler & jump_mask);
+                       uasm_i_nop(&buf);
+               } else {
+                       UASM_i_LA(&buf, k0, handler);
+                       uasm_i_jr(&buf, k0);
+                       uasm_i_nop(&buf);
+               }
+               local_flush_icache_range(ebase + 0x200, (unsigned long)buf);


I would expect that this causes section mismatch build warnings.

You may have to make this function __init or __cpu_init (and change trap_init() to __cpu_init too).

You should also fix the comment, as after the patch it is no longer accurate.

        }
        return (void *)old_handler;
 }




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