Merge Qualcom Hexagon architecture

This is the fifth version of the patchset (with one tiny whitespace fix)
to the Linux kernel to support the Qualcomm Hexagon architecture.

Between now and the next pull requests, Richard Kuo should have his key
signed, etc., and should be back on kernel.org.  In the meantime, this
got merged as a emailed patch-series.

* Hexagon: (36 commits)
  Add extra arch overrides to asm-generic/checksum.h
  Hexagon: Add self to MAINTAINERS
  Hexagon: Add basic stacktrace functionality for Hexagon architecture.
  Hexagon: Add configuration and makefiles for the Hexagon architecture.
  Hexagon: Comet platform support
  Hexagon: kgdb support files
  Hexagon: Add page-fault support.
  Hexagon: Add page table header files & etc.
  Hexagon: Add ioremap support
  Hexagon: Provide DMA implementation
  Hexagon: Implement basic TLB management routines for Hexagon.
  Hexagon: Implement basic cache-flush support
  Hexagon: Provide basic implementation and/or stubs for I/O routines.
  Hexagon: Add user access functions
  Hexagon: Add locking types and functions
  Hexagon: Add SMP support
  Hexagon: Provide basic debugging and system trap support.
  Hexagon: Add ptrace support
  Hexagon: Add time and timer functions
  Hexagon: Add interrupts
  ...

1 files changed, 95 insertions, 0 deletions

diff --git a/arch/hexagon/kernel/vm_switch.S b/arch/hexagon/kernel/vm_switch.S
new file mode 100644
index 0000000..0decf2f
--- /dev/null
+++ b/arch/hexagon/kernel/vm_switch.S
@@ -0,0 +1,95 @@
+/*
+ * Context switch support 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 <asm/asm-offsets.h>
+
+.text
+
+/*
+ * The register used as a fast-path thread information pointer
+ * is determined as a kernel configuration option.  If it happens
+ * to be a callee-save register, we're going to be saving and
+ * restoring it twice here.
+ *
+ * This code anticipates a revised ABI where R20-23 are added
+ * to the set of callee-save registers, but this should be
+ * backward compatible to legacy tools.
+ */
+
+
+/*
+ *	void switch_to(struct task_struct *prev,
+ *		struct task_struct *next, struct task_struct *last);
+ */
+	.p2align 2
+	.globl __switch_to
+	.type	__switch_to, @function
+
+/*
+ * When we exit the wormhole, we need to store the previous task
+ * in the new R0's pointer.  Technically it should be R2, but they should
+ * be the same; seems like a legacy thing.  In short, don't butcher
+ * R0, let it go back out unmolested.
+ */
+
+__switch_to:
+	/*
+	 * Push callee-saves onto "prev" stack.
+	 * Here, we're sneaky because the LR and FP
+	 * storage of the thread_stack structure
+	 * is automagically allocated by allocframe,
+	 * so we pass struct size less 8.
+	 */
+	allocframe(#(_SWITCH_STACK_SIZE - 8));
+	memd(R29+#(_SWITCH_R2726))=R27:26;
+	memd(R29+#(_SWITCH_R2524))=R25:24;
+	memd(R29+#(_SWITCH_R2322))=R23:22;
+	memd(R29+#(_SWITCH_R2120))=R21:20;
+	memd(R29+#(_SWITCH_R1918))=R19:18;
+	memd(R29+#(_SWITCH_R1716))=R17:16;
+	/* Stash thread_info pointer in task_struct */
+	memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG;
+	memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29;
+	/* Switch to "next" stack and restore callee saves from there */
+	R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP));
+	{
+	    R27:26 = memd(R29+#(_SWITCH_R2726));
+	    R25:24 = memd(R29+#(_SWITCH_R2524));
+	}
+	{
+	    R23:22 = memd(R29+#(_SWITCH_R2322));
+	    R21:20 = memd(R29+#(_SWITCH_R2120));
+	}
+	{
+	    R19:18 = memd(R29+#(_SWITCH_R1918));
+	    R17:16 = memd(R29+#(_SWITCH_R1716));
+	}
+	{
+	    /* THREADINFO_REG is currently one of the callee-saved regs
+	     * above, and so be sure to re-load it last.
+	     */
+	    THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO);
+	    R31:30 = memd(R29+#_SWITCH_FP);
+	}
+	{
+	    R29 = add(R29,#_SWITCH_STACK_SIZE);
+	    jumpr R31;
+	}
+	.size	__switch_to, .-__switch_to