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authorHaavard Skinnemoen <hskinnemoen@atmel.com>2006-09-25 23:32:13 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-26 08:48:54 -0700
commit5f97f7f9400de47ae837170bb274e90ad3934386 (patch)
tree514451e6dc6b46253293a00035d375e77b1c65ed /arch/avr32/kernel/semaphore.c
parent53e62d3aaa60590d4a69b4e07c29f448b5151047 (diff)
[PATCH] avr32 architecture
This adds support for the Atmel AVR32 architecture as well as the AT32AP7000 CPU and the AT32STK1000 development board. AVR32 is a new high-performance 32-bit RISC microprocessor core, designed for cost-sensitive embedded applications, with particular emphasis on low power consumption and high code density. The AVR32 architecture is not binary compatible with earlier 8-bit AVR architectures. The AVR32 architecture, including the instruction set, is described by the AVR32 Architecture Manual, available from http://www.atmel.com/dyn/resources/prod_documents/doc32000.pdf The Atmel AT32AP7000 is the first CPU implementing the AVR32 architecture. It features a 7-stage pipeline, 16KB instruction and data caches and a full Memory Management Unit. It also comes with a large set of integrated peripherals, many of which are shared with the AT91 ARM-based controllers from Atmel. Full data sheet is available from http://www.atmel.com/dyn/resources/prod_documents/doc32003.pdf while the CPU core implementation including caches and MMU is documented by the AVR32 AP Technical Reference, available from http://www.atmel.com/dyn/resources/prod_documents/doc32001.pdf Information about the AT32STK1000 development board can be found at http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3918 including a BSP CD image with an earlier version of this patch, development tools (binaries and source/patches) and a root filesystem image suitable for booting from SD card. Alternatively, there's a preliminary "getting started" guide available at http://avr32linux.org/twiki/bin/view/Main/GettingStarted which provides links to the sources and patches you will need in order to set up a cross-compiling environment for avr32-linux. This patch, as well as the other patches included with the BSP and the toolchain patches, is actively supported by Atmel Corporation. [dmccr@us.ibm.com: Fix more pxx_page macro locations] [bunk@stusta.de: fix `make defconfig'] Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Dave McCracken <dmccr@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/avr32/kernel/semaphore.c')
-rw-r--r--arch/avr32/kernel/semaphore.c148
1 files changed, 148 insertions, 0 deletions
diff --git a/arch/avr32/kernel/semaphore.c b/arch/avr32/kernel/semaphore.c
new file mode 100644
index 00000000000..1e2705a0501
--- /dev/null
+++ b/arch/avr32/kernel/semaphore.c
@@ -0,0 +1,148 @@
+/*
+ * AVR32 sempahore implementation.
+ *
+ * Copyright (C) 2004-2006 Atmel Corporation
+ *
+ * Based on linux/arch/i386/kernel/semaphore.c
+ * Copyright (C) 1999 Linus Torvalds
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/sched.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+
+#include <asm/semaphore.h>
+#include <asm/atomic.h>
+
+/*
+ * Semaphores are implemented using a two-way counter:
+ * The "count" variable is decremented for each process
+ * that tries to acquire the semaphore, while the "sleeping"
+ * variable is a count of such acquires.
+ *
+ * Notably, the inline "up()" and "down()" functions can
+ * efficiently test if they need to do any extra work (up
+ * needs to do something only if count was negative before
+ * the increment operation.
+ *
+ * "sleeping" and the contention routine ordering is protected
+ * by the spinlock in the semaphore's waitqueue head.
+ *
+ * Note that these functions are only called when there is
+ * contention on the lock, and as such all this is the
+ * "non-critical" part of the whole semaphore business. The
+ * critical part is the inline stuff in <asm/semaphore.h>
+ * where we want to avoid any extra jumps and calls.
+ */
+
+/*
+ * Logic:
+ * - only on a boundary condition do we need to care. When we go
+ * from a negative count to a non-negative, we wake people up.
+ * - when we go from a non-negative count to a negative do we
+ * (a) synchronize with the "sleeper" count and (b) make sure
+ * that we're on the wakeup list before we synchronize so that
+ * we cannot lose wakeup events.
+ */
+
+void __up(struct semaphore *sem)
+{
+ wake_up(&sem->wait);
+}
+EXPORT_SYMBOL(__up);
+
+void __sched __down(struct semaphore *sem)
+{
+ struct task_struct *tsk = current;
+ DECLARE_WAITQUEUE(wait, tsk);
+ unsigned long flags;
+
+ tsk->state = TASK_UNINTERRUPTIBLE;
+ spin_lock_irqsave(&sem->wait.lock, flags);
+ add_wait_queue_exclusive_locked(&sem->wait, &wait);
+
+ sem->sleepers++;
+ for (;;) {
+ int sleepers = sem->sleepers;
+
+ /*
+ * Add "everybody else" into it. They aren't
+ * playing, because we own the spinlock in
+ * the wait_queue_head.
+ */
+ if (atomic_add_return(sleepers - 1, &sem->count) >= 0) {
+ sem->sleepers = 0;
+ break;
+ }
+ sem->sleepers = 1; /* us - see -1 above */
+ spin_unlock_irqrestore(&sem->wait.lock, flags);
+
+ schedule();
+
+ spin_lock_irqsave(&sem->wait.lock, flags);
+ tsk->state = TASK_UNINTERRUPTIBLE;
+ }
+ remove_wait_queue_locked(&sem->wait, &wait);
+ wake_up_locked(&sem->wait);
+ spin_unlock_irqrestore(&sem->wait.lock, flags);
+ tsk->state = TASK_RUNNING;
+}
+EXPORT_SYMBOL(__down);
+
+int __sched __down_interruptible(struct semaphore *sem)
+{
+ int retval = 0;
+ struct task_struct *tsk = current;
+ DECLARE_WAITQUEUE(wait, tsk);
+ unsigned long flags;
+
+ tsk->state = TASK_INTERRUPTIBLE;
+ spin_lock_irqsave(&sem->wait.lock, flags);
+ add_wait_queue_exclusive_locked(&sem->wait, &wait);
+
+ sem->sleepers++;
+ for (;;) {
+ int sleepers = sem->sleepers;
+
+ /*
+ * With signals pending, this turns into the trylock
+ * failure case - we won't be sleeping, and we can't
+ * get the lock as it has contention. Just correct the
+ * count and exit.
+ */
+ if (signal_pending(current)) {
+ retval = -EINTR;
+ sem->sleepers = 0;
+ atomic_add(sleepers, &sem->count);
+ break;
+ }
+
+ /*
+ * Add "everybody else" into it. They aren't
+ * playing, because we own the spinlock in
+ * the wait_queue_head.
+ */
+ if (atomic_add_return(sleepers - 1, &sem->count) >= 0) {
+ sem->sleepers = 0;
+ break;
+ }
+ sem->sleepers = 1; /* us - see -1 above */
+ spin_unlock_irqrestore(&sem->wait.lock, flags);
+
+ schedule();
+
+ spin_lock_irqsave(&sem->wait.lock, flags);
+ tsk->state = TASK_INTERRUPTIBLE;
+ }
+ remove_wait_queue_locked(&sem->wait, &wait);
+ wake_up_locked(&sem->wait);
+ spin_unlock_irqrestore(&sem->wait.lock, flags);
+
+ tsk->state = TASK_RUNNING;
+ return retval;
+}
+EXPORT_SYMBOL(__down_interruptible);