Fixed MTP to work with TWRP

arch/arm/kernel/pj4-cp0.c

@@ -0,0 +1,133 @@
+/*
+ * linux/arch/arm/kernel/pj4-cp0.c
+ *
+ * PJ4 iWMMXt coprocessor context switching and handling
+ *
+ * Copyright (c) 2010 Marvell International Inc.
+ *
+ * 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/types.h>
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <asm/thread_notify.h>
+#include <asm/cputype.h>
+
+static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
+{
+	struct thread_info *thread = t;
+
+	switch (cmd) {
+	case THREAD_NOTIFY_FLUSH:
+		/*
+		 * flush_thread() zeroes thread->fpstate, so no need
+		 * to do anything here.
+		 *
+		 * FALLTHROUGH: Ensure we don't try to overwrite our newly
+		 * initialised state information on the first fault.
+		 */
+
+	case THREAD_NOTIFY_EXIT:
+		iwmmxt_task_release(thread);
+		break;
+
+	case THREAD_NOTIFY_SWITCH:
+		iwmmxt_task_switch(thread);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block __maybe_unused iwmmxt_notifier_block = {
+	.notifier_call	= iwmmxt_do,
+};
+
+
+static u32 __init pj4_cp_access_read(void)
+{
+	u32 value;
+
+	__asm__ __volatile__ (
+		"mrc	p15, 0, %0, c1, c0, 2\n\t"
+		: "=r" (value));
+	return value;
+}
+
+static void __init pj4_cp_access_write(u32 value)
+{
+	u32 temp;
+
+	__asm__ __volatile__ (
+		"mcr	p15, 0, %1, c1, c0, 2\n\t"
+		"mrc	p15, 0, %0, c1, c0, 2\n\t"
+		"mov	%0, %0\n\t"
+		"sub	pc, pc, #4\n\t"
+		: "=r" (temp) : "r" (value));
+}
+
+static int __init pj4_get_iwmmxt_version(void)
+{
+	u32 cp_access, wcid;
+
+	cp_access = pj4_cp_access_read();
+	pj4_cp_access_write(cp_access | 0xf);
+
+	/* check if coprocessor 0 and 1 are available */
+	if ((pj4_cp_access_read() & 0xf) != 0xf) {
+		pj4_cp_access_write(cp_access);
+		return -ENODEV;
+	}
+
+	/* read iWMMXt coprocessor id register p1, c0 */
+	__asm__ __volatile__ ("mrc    p1, 0, %0, c0, c0, 0\n" : "=r" (wcid));
+
+	pj4_cp_access_write(cp_access);
+
+	/* iWMMXt v1 */
+	if ((wcid & 0xffffff00) == 0x56051000)
+		return 1;
+	/* iWMMXt v2 */
+	if ((wcid & 0xffffff00) == 0x56052000)
+		return 2;
+
+	return -EINVAL;
+}
+
+/*
+ * Disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
+ * switch code handle iWMMXt context switching.
+ */
+static int __init pj4_cp0_init(void)
+{
+	u32 __maybe_unused cp_access;
+	int vers;
+
+	if (!cpu_is_pj4())
+		return 0;
+
+	vers = pj4_get_iwmmxt_version();
+	if (vers < 0)
+		return 0;
+
+#ifndef CONFIG_IWMMXT
+	pr_info("PJ4 iWMMXt coprocessor detected, but kernel support is missing.\n");
+#else
+	cp_access = pj4_cp_access_read() & ~0xf;
+	pj4_cp_access_write(cp_access);
+
+	pr_info("PJ4 iWMMXt v%d coprocessor enabled.\n", vers);
+	elf_hwcap |= HWCAP_IWMMXT;
+	thread_register_notifier(&iwmmxt_notifier_block);
+#endif
+
+	return 0;
+}
+
+late_initcall(pj4_cp0_init);