ARMv7: Add support for the ThumbEE state saving/restoring

This patch adds the detection and handling of the ThumbEE extension on
ARMv7 CPUs.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 81 insertions, 0 deletions

diff --git a/arch/arm/kernel/thumbee.c b/arch/arm/kernel/thumbee.c
new file mode 100644
index 0000000..df3f6b7
--- /dev/null
+++ b/arch/arm/kernel/thumbee.c
@@ -0,0 +1,81 @@
+/*
+ * arch/arm/kernel/thumbee.c
+ *
+ * Copyright (C) 2008 ARM Limited
+ *
+ * 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.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include <asm/thread_notify.h>
+
+/*
+ * Access to the ThumbEE Handler Base register
+ */
+static inline unsigned long teehbr_read()
+{
+	unsigned long v;
+	asm("mrc	p14, 6, %0, c1, c0, 0\n" : "=r" (v));
+	return v;
+}
+
+static inline void teehbr_write(unsigned long v)
+{
+	asm("mcr	p14, 6, %0, c1, c0, 0\n" : : "r" (v));
+}
+
+static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void *t)
+{
+	struct thread_info *thread = t;
+
+	switch (cmd) {
+	case THREAD_NOTIFY_FLUSH:
+		thread->thumbee_state = 0;
+		break;
+	case THREAD_NOTIFY_SWITCH:
+		current_thread_info()->thumbee_state = teehbr_read();
+		teehbr_write(thread->thumbee_state);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block thumbee_notifier_block = {
+	.notifier_call	= thumbee_notifier,
+};
+
+static int __init thumbee_init(void)
+{
+	unsigned long pfr0;
+	unsigned int cpu_arch = cpu_architecture();
+
+	if (cpu_arch < CPU_ARCH_ARMv7)
+		return 0;
+
+	/* processor feature register 0 */
+	asm("mrc	p15, 0, %0, c0, c1, 0\n" : "=r" (pfr0));
+	if ((pfr0 & 0x0000f000) != 0x00001000)
+		return 0;
+
+	printk(KERN_INFO "ThumbEE CPU extension supported.\n");
+	elf_hwcap |= HWCAP_THUMBEE;
+	thread_register_notifier(&thumbee_notifier_block);
+
+	return 0;
+}
+
+late_initcall(thumbee_init);