From 3c031c5ab96818783c4381a6ace397c76fe3f34a Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Mon, 22 Apr 2002 12:07:34 +0000
Subject: simple collaborate multitasking scheduler donated to us by Ulf
 Ralberg

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@170 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/thread.c | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 firmware/thread.c

(limited to 'firmware/thread.c')

diff --git a/firmware/thread.c b/firmware/thread.c
new file mode 100644
index 0000000000..1db23e0fa4
--- /dev/null
+++ b/firmware/thread.c
@@ -0,0 +1,159 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2002 by Ulf Ralberg
+ *
+ * All files in this archive are subject to the GNU General Public License.
+ * See the file COPYING in the source tree root for full license agreement.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "thread.h"
+
+typedef union
+{
+  struct regs_t
+  {
+    void*	lr;
+    u_int32_t	cr;
+    void*	sp;
+  } regs;
+  u_int32_t	mem[32];
+} ctx_t;
+
+typedef struct
+{
+  int		created;
+  int		current;
+  ctx_t		ctx[MAXTHREADS] __attribute__ ((aligned (32)));
+} thread_t;
+
+static thread_t threads = {1, 0};
+
+/*--------------------------------------------------------------------------- 
+ * Store non-volatile context.
+ *---------------------------------------------------------------------------
+ */
+static inline void
+stctx(void*	addr)
+{
+  u_int32_t	tmp;
+
+  __asm__ __volatile__ ("mflr %0" : "=r" (tmp));
+  __asm__ __volatile__ ("stw  %0,0(%1)" :: "r" (tmp), "b" (addr) : "memory");
+  __asm__ __volatile__ ("mfcr %0" : "=r" (tmp));
+  __asm__ __volatile__ ("stw  %0,4(%1)" :: "r" (tmp), "b" (addr) : "memory");
+  __asm__ __volatile__ ("stw 1, 8(%0)\n\t"
+			"stw 2, 12(%0)\n\t"
+			"stw 13,16(%0)\n\t"
+			"stw 14,20(%0)\n\t"
+			"stw 15,24(%0)\n\t"
+			"stw 16,28(%0)\n\t"
+			"stw 17,32(%0)\n\t"
+			"stw 18,36(%0)\n\t"
+			"stw 19,40(%0)\n\t"
+			"stw 20,44(%0)\n\t"
+			"stw 21,48(%0)\n\t"
+			"stw 22,52(%0)\n\t"
+			"stw 23,56(%0)\n\t"
+			"stw 24,60(%0)\n\t"
+			"stw 25,64(%0)\n\t"
+			"stw 26,68(%0)\n\t"
+			"stw 27,72(%0)\n\t"
+			"stw 28,76(%0)\n\t"
+			"stw 29,80(%0)\n\t"
+			"stw 30,84(%0)\n\t"
+			"stw 31,88(%0)\n\t"
+			:: "b" (addr) : "memory");
+}
+
+/*--------------------------------------------------------------------------- 
+ * Load non-volatile context.
+ *---------------------------------------------------------------------------
+ */
+static inline void
+ldctx(void*	addr)
+{
+  u_int32_t	tmp;
+
+  __asm__ __volatile__ ("lwz  %0,0(%1)" : "=r" (tmp): "b" (addr) : "memory");
+  __asm__ __volatile__ ("mtlr %0" : "=r" (tmp));
+  __asm__ __volatile__ ("lwz  %0,4(%1)" : "=r" (tmp): "b" (addr) : "memory");
+  __asm__ __volatile__ ("mtcr %0" : "=r" (tmp));
+  __asm__ __volatile__ ("lwz 1, 8(%0)\n\t"
+			"lwz 2, 12(%0)\n\t"
+			"lwz 13,16(%0)\n\t"
+			"lwz 14,20(%0)\n\t"
+			"lwz 15,24(%0)\n\t"
+			"lwz 16,28(%0)\n\t"
+			"lwz 17,32(%0)\n\t"
+			"lwz 18,36(%0)\n\t"
+			"lwz 19,40(%0)\n\t"
+			"lwz 20,44(%0)\n\t"
+			"lwz 21,48(%0)\n\t"
+			"lwz 22,52(%0)\n\t"
+			"lwz 23,56(%0)\n\t"
+			"lwz 24,60(%0)\n\t"
+			"lwz 25,64(%0)\n\t"
+			"lwz 26,68(%0)\n\t"
+			"lwz 27,72(%0)\n\t"
+			"lwz 28,76(%0)\n\t"
+			"lwz 29,80(%0)\n\t"
+			"lwz 30,84(%0)\n\t"
+			"lwz 31,88(%0)\n\t"
+			:: "b" (addr) : "memory");
+}
+
+/*--------------------------------------------------------------------------- 
+ * Switch thread in round robin fashion.
+ *---------------------------------------------------------------------------
+ */
+void
+switch_thread(void)
+{
+  int		ct;
+  int		nt;
+  thread_t*	t = &threads;
+
+  nt = ct = t->current;
+  if (++nt >= t->created)
+    nt = 0;
+  t->current = nt;
+  stctx(&t->ctx[ct]);
+  ldctx(&t->ctx[nt]);
+}
+
+/*--------------------------------------------------------------------------- 
+ * Create thread. Stack is aligned at 32 byte boundary to fit cache line.
+ * > 220 bytes allocated on top for exception handlers as per EABI spec.
+ * Return 0 if context area could be allocated, else -1.
+ *---------------------------------------------------------------------------
+ */
+int
+create_thread(void*	fp,
+	      void*	sp,
+	      int	stk_size)
+{
+  thread_t*		t = &threads;
+
+  if (t->created >= MAXTHREADS)
+    return -1;
+  else
+    {
+      ctx_t* ctxp = &t->ctx[t->created++];
+      stctx(ctxp);
+      ctxp->regs.sp = (void*)(((u_int32_t)sp + stk_size - 256) & ~31);
+      ctxp->regs.lr = fp;
+    }
+  return 0;
+}
+
+/* eof */
-- 
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