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arch/arm/src/armv7-m/iar/up_testset.S

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+/****************************************************************************
+ * arch/arm/src/armv7-m/gnu/up_testset.S
+ *
+ *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <arch/spinlock.h>
+
+	MODULE up_testset
+	SECTION .text:CODE:NOROOT(2)
+
+/****************************************************************************
+ * Public Symbols
+ ****************************************************************************/
+
+	PUBLIC up_testset
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: up_testset
+ *
+ * Description:
+ *   Perform and atomic test and set operation on the provided spinlock.
+ *
+ *   This function must be provided via the architecture-specific logoic.
+ *
+ * Input Parameters:
+ *   lock - The address of spinlock object.
+ *
+ * Returned Value:
+ *   The spinlock is always locked upon return.  The value of previous value
+ *   of the spinlock variable is returned, either SP_LOCKED if the spinlock
+ *   as previously locked (meaning that the test-and-set operation failed to
+ *   obtain the lock) or SP_UNLOCKED if the spinlock was previously unlocked
+ *   (meaning that we successfully obtained the lock)
+ *
+ ****************************************************************************/
+
+	THUMB
+
+up_testset:
+
+	mov		r1, #SP_LOCKED
+
+	/* Test if the spinlock is locked or not */
+
+L1:
+	ldrexb	r2, [r0]			/* Test if spinlock is locked or not */
+	cmp		r2, r1				/* Already locked? */
+	beq		L2					/* If already locked, return SP_LOCKED */
+
+	/* Not locked ... attempt to lock it */
+
+	strexb	r2, r1, [r0]		/* Attempt to set the locked state */
+	cmp		r2, r1				/* r2 will be 1 is strexb failed */
+	beq		1b					/* Failed to lock... try again */
+
+	/* Lock acquired -- return SP_UNLOCKED */
+
+	dmb							/* Required before accessing protected resource */
+	mov		r0, #SP_UNLOCKED
+	bx		lr
+
+	/* Lock not acquired -- return SP_LOCKED */
+
+L2:
+	mov		r0, #SP_LOCKED
+	bx		lr
+
+	END