From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 arch/arm/kernel/xscale-cp0.c | 177 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)
 create mode 100644 arch/arm/kernel/xscale-cp0.c

(limited to 'arch/arm/kernel/xscale-cp0.c')

diff --git a/arch/arm/kernel/xscale-cp0.c b/arch/arm/kernel/xscale-cp0.c
new file mode 100644
index 000000000..bdbb8853a
--- /dev/null
+++ b/arch/arm/kernel/xscale-cp0.c
@@ -0,0 +1,177 @@
+/*
+ * linux/arch/arm/kernel/xscale-cp0.c
+ *
+ * XScale DSP and iWMMXt coprocessor context switching and handling
+ *
+ * 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>
+
+static inline void dsp_save_state(u32 *state)
+{
+	__asm__ __volatile__ (
+		"mrrc	p0, 0, %0, %1, c0\n"
+		: "=r" (state[0]), "=r" (state[1]));
+}
+
+static inline void dsp_load_state(u32 *state)
+{
+	__asm__ __volatile__ (
+		"mcrr	p0, 0, %0, %1, c0\n"
+		: : "r" (state[0]), "r" (state[1]));
+}
+
+static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t)
+{
+	struct thread_info *thread = t;
+
+	switch (cmd) {
+	case THREAD_NOTIFY_FLUSH:
+		thread->cpu_context.extra[0] = 0;
+		thread->cpu_context.extra[1] = 0;
+		break;
+
+	case THREAD_NOTIFY_SWITCH:
+		dsp_save_state(current_thread_info()->cpu_context.extra);
+		dsp_load_state(thread->cpu_context.extra);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block dsp_notifier_block = {
+	.notifier_call	= dsp_do,
+};
+
+
+#ifdef CONFIG_IWMMXT
+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 iwmmxt_notifier_block = {
+	.notifier_call	= iwmmxt_do,
+};
+#endif
+
+
+static u32 __init xscale_cp_access_read(void)
+{
+	u32 value;
+
+	__asm__ __volatile__ (
+		"mrc	p15, 0, %0, c15, c1, 0\n\t"
+		: "=r" (value));
+
+	return value;
+}
+
+static void __init xscale_cp_access_write(u32 value)
+{
+	u32 temp;
+
+	__asm__ __volatile__ (
+		"mcr	p15, 0, %1, c15, c1, 0\n\t"
+		"mrc	p15, 0, %0, c15, c1, 0\n\t"
+		"mov	%0, %0\n\t"
+		"sub	pc, pc, #4\n\t"
+		: "=r" (temp) : "r" (value));
+}
+
+/*
+ * Detect whether we have a MAC coprocessor (40 bit register) or an
+ * iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000
+ * into a coprocessor register and reading it back, and checking
+ * whether the upper word survived intact.
+ */
+static int __init cpu_has_iwmmxt(void)
+{
+	u32 lo;
+	u32 hi;
+
+	/*
+	 * This sequence is interpreted by the DSP coprocessor as:
+	 *	mar	acc0, %2, %3
+	 *	mra	%0, %1, acc0
+	 *
+	 * And by the iWMMXt coprocessor as:
+	 *	tmcrr	wR0, %2, %3
+	 *	tmrrc	%0, %1, wR0
+	 */
+	__asm__ __volatile__ (
+		"mcrr	p0, 0, %2, %3, c0\n"
+		"mrrc	p0, 0, %0, %1, c0\n"
+		: "=r" (lo), "=r" (hi)
+		: "r" (0), "r" (0x100));
+
+	return !!hi;
+}
+
+
+/*
+ * If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we
+ * disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
+ * switch code handle iWMMXt context switching.  If on the other
+ * hand the CPU has a DSP coprocessor, we keep access to CP0 enabled
+ * all the time, and save/restore acc0 on context switch in non-lazy
+ * fashion.
+ */
+static int __init xscale_cp0_init(void)
+{
+	u32 cp_access;
+
+	cp_access = xscale_cp_access_read() & ~3;
+	xscale_cp_access_write(cp_access | 1);
+
+	if (cpu_has_iwmmxt()) {
+#ifndef CONFIG_IWMMXT
+		pr_warn("CAUTION: XScale iWMMXt coprocessor detected, but kernel support is missing.\n");
+#else
+		pr_info("XScale iWMMXt coprocessor detected.\n");
+		elf_hwcap |= HWCAP_IWMMXT;
+		thread_register_notifier(&iwmmxt_notifier_block);
+#endif
+	} else {
+		pr_info("XScale DSP coprocessor detected.\n");
+		thread_register_notifier(&dsp_notifier_block);
+		cp_access |= 1;
+	}
+
+	xscale_cp_access_write(cp_access);
+
+	return 0;
+}
+
+late_initcall(xscale_cp0_init);
-- 
cgit v1.2.3-54-g00ecf