Hexagon: Add startup code
Signed-off-by: Richard Kuo <rkuo@codeaurora.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/hexagon/kernel/head.S b/arch/hexagon/kernel/head.S
new file mode 100644
index 0000000..8e6b819
--- /dev/null
+++ b/arch/hexagon/kernel/head.S
@@ -0,0 +1,162 @@
+/*
+ * Early kernel startup code for Hexagon
+ *
+ * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include <linux/linkage.h>
+#include <linux/init.h>
+#include <asm/asm-offsets.h>
+#include <asm/mem-layout.h>
+#include <asm/vm_mmu.h>
+#include <asm/page.h>
+
+ __INIT
+ENTRY(stext)
+ /*
+ * VMM will already have set up true vector page, MMU, etc.
+ * To set up initial kernel identity map, we have to pass
+ * the VMM a pointer to some canonical page tables. In
+ * this implementation, we're assuming that we've got
+ * them precompiled. Generate value in R24, as we'll need
+ * it again shortly.
+ */
+ r24.L = #LO(swapper_pg_dir)
+ r24.H = #HI(swapper_pg_dir)
+
+ /*
+ * Symbol is kernel segment address, but we need
+ * the logical/physical address.
+ */
+ r24 = asl(r24, #2)
+ r24 = lsr(r24, #2)
+
+ r0 = r24
+
+ /*
+ * Initialize a 16MB PTE to make the virtual and physical
+ * addresses where the kernel was loaded be identical.
+ */
+#define PTE_BITS ( __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X \
+ | __HEXAGON_C_WB_L2 << 6 \
+ | __HVM_PDE_S_4MB)
+
+ r1 = pc
+ r2.H = #0xffc0
+ r2.L = #0x0000
+ r1 = and(r1,r2) /* round PC to 4MB boundary */
+ r2 = lsr(r1, #22) /* 4MB page number */
+ r2 = asl(r2, #2) /* times sizeof(PTE) (4bytes) */
+ r0 = add(r0,r2) /* r0 = address of correct PTE */
+ r2 = #PTE_BITS
+ r1 = add(r1,r2) /* r1 = 4MB PTE for the first entry */
+ r2.h = #0x0040
+ r2.l = #0x0000 /* 4MB */
+ memw(r0 ++ #4) = r1
+ r1 = add(r1, r2)
+ memw(r0 ++ #4) = r1
+
+ r0 = r24
+
+ /*
+ * The subroutine wrapper around the virtual instruction touches
+ * no memory, so we should be able to use it even here.
+ */
+ call __vmnewmap;
+
+ /* Jump into virtual address range. */
+
+ r31.h = #hi(__head_s_vaddr_target)
+ r31.l = #lo(__head_s_vaddr_target)
+ jumpr r31
+
+ /* Insert trippy space effects. */
+
+__head_s_vaddr_target:
+ /*
+ * Tear down VA=PA translation now that we are running
+ * in the desgnated kernel segments.
+ */
+ r0 = #__HVM_PDE_S_INVALID
+ r1 = r24
+ loop0(1f,#0x100)
+1:
+ {
+ memw(R1 ++ #4) = R0
+ }:endloop0
+
+ r0 = r24
+ call __vmnewmap
+
+ /* Go ahead and install the trap0 return so angel calls work */
+ r0.h = #hi(_K_provisional_vec)
+ r0.l = #lo(_K_provisional_vec)
+ call __vmsetvec
+
+ /*
+ * OK, at this point we should start to be much more careful,
+ * we're going to enter C code and start touching memory
+ * in all sorts of places.
+ * This means:
+ * SGP needs to be OK
+ * Need to lock shared resources
+ * A bunch of other things that will cause
+ * all kinds of painful bugs
+ */
+
+ /*
+ * Stack pointer should be pointed at the init task's
+ * thread stack, which should have been declared in arch/init_task.c.
+ * So uhhhhh...
+ * It's accessible via the init_thread_union, which is a union
+ * of a thread_info struct and a stack; of course, the top
+ * of the stack is not for you. The end of the stack
+ * is simply init_thread_union + THREAD_SIZE.
+ */
+
+ {r29.H = #HI(init_thread_union); r0.H = #HI(_THREAD_SIZE); }
+ {r29.L = #LO(init_thread_union); r0.L = #LO(_THREAD_SIZE); }
+
+ /* initialize the register used to point to current_thread_info */
+ /* Fixme: THREADINFO_REG can't be R2 because of that memset thing. */
+ {r29 = add(r29,r0); THREADINFO_REG = r29; }
+
+ /* Hack: zero bss; */
+ { r0.L = #LO(__bss_start); r1 = #0; r2.l = #LO(__bss_stop); }
+ { r0.H = #HI(__bss_start); r2.h = #HI(__bss_stop); }
+
+ r2 = sub(r2,r0);
+ call memset;
+
+ /* Time to make the doughnuts. */
+ call start_kernel
+
+ /*
+ * Should not reach here.
+ */
+1:
+ jump 1b
+
+.p2align PAGE_SHIFT
+ENTRY(external_cmdline_buffer)
+ .fill _PAGE_SIZE,1,0
+
+.data
+.p2align PAGE_SHIFT
+ENTRY(empty_zero_page)
+ .fill _PAGE_SIZE,1,0