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authorThomas Martitz <kugel@rockbox.org>2011-02-18 22:46:01 +0000
committerThomas Martitz <kugel@rockbox.org>2011-02-18 22:46:01 +0000
commit6d85de341928aef8178465c60122f3cbe76f5dd6 (patch)
treeff86c384a574ac20d3418c1b904ed4d0de1f6980 /firmware/target/hosted/thread-arm.c
parent3926c30705cc7235122e2f2e35ab506b53238cdf (diff)
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Implement cooperative threads on hosted platforms using C code.
This replaces SDL threads with real cooperative threads, which are less cpu intensive and allow priority scheduling. The backend for context switching is dependant on the host (sigaltstack/longjmp on Unix, Fibers on Windows). configure has options to force or disallow SDL threads. git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29327 a1c6a512-1295-4272-9138-f99709370657
Diffstat (limited to 'firmware/target/hosted/thread-arm.c')
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1 files changed, 98 insertions, 0 deletions
diff --git a/firmware/target/hosted/thread-arm.c b/firmware/target/hosted/thread-arm.c
new file mode 100644
index 0000000000..d2fa7d1e5d
--- /dev/null
+++ b/firmware/target/hosted/thread-arm.c
@@ -0,0 +1,98 @@
+/***************************************************************************
+ * __________ __ ___.
+ * Open \______ \ ____ ____ | | _\_ |__ _______ ___
+ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
+ * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
+ * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
+ * \/ \/ \/ \/ \/
+ * $Id$
+ *
+ * Copyright (C) 2005 by Thom Johansen
+ * Copyright (C) 2010 by Thomas Martitz (Android-suitable core_sleep())
+ *
+ * Generic ARM threading support
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include <system.h>
+/*---------------------------------------------------------------------------
+ * Start the thread running and terminate it if it returns
+ *---------------------------------------------------------------------------
+ */
+static void __attribute__((naked,used)) start_thread(void)
+{
+ /* r0 = context */
+ asm volatile (
+ "ldr sp, [r0, #32] \n" /* Load initial sp */
+ "ldr r4, [r0, #40] \n" /* start in r4 since it's non-volatile */
+ "mov r1, #0 \n" /* Mark thread as running */
+ "str r1, [r0, #40] \n"
+ "mov lr, pc \n" /* Call thread function */
+ "bx r4 \n"
+ ); /* No clobber list - new thread doesn't care */
+ thread_exit();
+}
+
+/* For startup, place context pointer in r4 slot, start_thread pointer in r5
+ * slot, and thread function pointer in context.start. See load_context for
+ * what happens when thread is initially going to run. */
+#define THREAD_STARTUP_INIT(core, thread, function) \
+ ({ (thread)->context.r[0] = (uint32_t)&(thread)->context, \
+ (thread)->context.r[1] = (uint32_t)start_thread, \
+ (thread)->context.start = (uint32_t)function; })
+
+
+/*---------------------------------------------------------------------------
+ * Store non-volatile context.
+ *---------------------------------------------------------------------------
+ */
+static inline void store_context(void* addr)
+{
+ asm volatile(
+ "stmia %0, { r4-r11, sp, lr } \n"
+ : : "r" (addr)
+ );
+}
+
+/*---------------------------------------------------------------------------
+ * Load non-volatile context.
+ *---------------------------------------------------------------------------
+ */
+static inline void load_context(const void* addr)
+{
+ asm volatile(
+ "ldr r0, [%0, #40] \n" /* Load start pointer */
+ "cmp r0, #0 \n" /* Check for NULL */
+
+ /* If not already running, jump to start */
+ "ldmneia %0, { r0, pc } \n"
+ "ldmia %0, { r4-r11, sp, lr } \n" /* Load regs r4 to r14 from context */
+ : : "r" (addr) : "r0" /* only! */
+ );
+}
+
+/*
+ * this core sleep suspends the OS thread rockbox runs under, which greatly
+ * reduces cpu usage (~100% to <10%)
+ *
+ * it returns when when the tick timer is called, other interrupt-like
+ * events occur
+ *
+ * wait_for_interrupt is implemented in kernel-<platform>.c
+ **/
+
+static inline void core_sleep(void)
+{
+ enable_irq();
+ wait_for_interrupt();
+}
+
+