C6X: process management

Original port to early 2.6 kernel using TI COFF toolchain.
Brought up to date by Mark Salter <msalter@redhat.com>

Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

2 files changed, 337 insertions, 0 deletions

diff --git a/arch/c6x/kernel/process.c b/arch/c6x/kernel/process.c
new file mode 100644
index 0000000..aa65c87
--- /dev/null
+++ b/arch/c6x/kernel/process.c
@@ -0,0 +1,263 @@
+/*
+ *  Port on Texas Instruments TMS320C6x architecture
+ *
+ *  Copyright (C) 2004, 2006, 2009, 2010, 2011 Texas Instruments Incorporated
+ *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
+ *
+ *  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/module.h>
+#include <linux/unistd.h>
+#include <linux/ptrace.h>
+#include <linux/init_task.h>
+#include <linux/tick.h>
+#include <linux/mqueue.h>
+#include <linux/syscalls.h>
+#include <linux/reboot.h>
+
+#include <asm/syscalls.h>
+
+/* hooks for board specific support */
+void	(*c6x_restart)(void);
+void	(*c6x_halt)(void);
+
+extern asmlinkage void ret_from_fork(void);
+
+static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
+static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);
+
+/*
+ * Initial thread structure.
+ */
+union thread_union init_thread_union __init_task_data =	{
+	INIT_THREAD_INFO(init_task)
+};
+
+/*
+ * Initial task structure.
+ */
+struct task_struct init_task = INIT_TASK(init_task);
+EXPORT_SYMBOL(init_task);
+
+/*
+ * power off function, if any
+ */
+void (*pm_power_off)(void);
+EXPORT_SYMBOL(pm_power_off);
+
+static void c6x_idle(void)
+{
+	unsigned long tmp;
+
+	/*
+	 * Put local_irq_enable and idle in same execute packet
+	 * to make them atomic and avoid race to idle with
+	 * interrupts enabled.
+	 */
+	asm volatile ("   mvc .s2 CSR,%0\n"
+		      "   or  .d2 1,%0,%0\n"
+		      "   mvc .s2 %0,CSR\n"
+		      "|| idle\n"
+		      : "=b"(tmp));
+}
+
+/*
+ * The idle loop for C64x
+ */
+void cpu_idle(void)
+{
+	/* endless idle loop with no priority at all */
+	while (1) {
+		tick_nohz_stop_sched_tick(1);
+		while (1) {
+			local_irq_disable();
+			if (need_resched()) {
+				local_irq_enable();
+				break;
+			}
+			c6x_idle(); /* enables local irqs */
+		}
+		tick_nohz_restart_sched_tick();
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
+}
+
+static void halt_loop(void)
+{
+	printk(KERN_EMERG "System Halted, OK to turn off power\n");
+	local_irq_disable();
+	while (1)
+		asm volatile("idle\n");
+}
+
+void machine_restart(char *__unused)
+{
+	if (c6x_restart)
+		c6x_restart();
+	halt_loop();
+}
+
+void machine_halt(void)
+{
+	if (c6x_halt)
+		c6x_halt();
+	halt_loop();
+}
+
+void machine_power_off(void)
+{
+	if (pm_power_off)
+		pm_power_off();
+	halt_loop();
+}
+
+static void kernel_thread_helper(int dummy, void *arg, int (*fn)(void *))
+{
+	do_exit(fn(arg));
+}
+
+/*
+ * Create a kernel thread
+ */
+int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
+{
+	struct pt_regs regs;
+
+	/*
+	 * copy_thread sets a4 to zero (child return from fork)
+	 * so we can't just set things up to directly return to
+	 * fn.
+	 */
+	memset(&regs, 0, sizeof(regs));
+	regs.b4 = (unsigned long) arg;
+	regs.a6 = (unsigned long) fn;
+	regs.pc = (unsigned long) kernel_thread_helper;
+	local_save_flags(regs.csr);
+	regs.csr |= 1;
+	regs.tsr = 5; /* Set GEE and GIE in TSR */
+
+	/* Ok, create the new process.. */
+	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, -1, &regs,
+		       0, NULL, NULL);
+}
+EXPORT_SYMBOL(kernel_thread);
+
+void flush_thread(void)
+{
+}
+
+void exit_thread(void)
+{
+}
+
+SYSCALL_DEFINE1(c6x_clone, struct pt_regs *, regs)
+{
+	unsigned long clone_flags;
+	unsigned long newsp;
+
+	/* syscall puts clone_flags in A4 and usp in B4 */
+	clone_flags = regs->orig_a4;
+	if (regs->b4)
+		newsp = regs->b4;
+	else
+		newsp = regs->sp;
+
+	return do_fork(clone_flags, newsp, regs, 0, (int __user *)regs->a6,
+		       (int __user *)regs->b6);
+}
+
+/*
+ * Do necessary setup to start up a newly executed thread.
+ */
+void start_thread(struct pt_regs *regs, unsigned int pc, unsigned long usp)
+{
+	/*
+	 * The binfmt loader will setup a "full" stack, but the C6X
+	 * operates an "empty" stack. So we adjust the usp so that
+	 * argc doesn't get destroyed if an interrupt is taken before
+	 * it is read from the stack.
+	 *
+	 * NB: Library startup code needs to match this.
+	 */
+	usp -= 8;
+
+	set_fs(USER_DS);
+	regs->pc  = pc;
+	regs->sp  = usp;
+	regs->tsr |= 0x40; /* set user mode */
+	current->thread.usp = usp;
+}
+
+/*
+ * Copy a new thread context in its stack.
+ */
+int copy_thread(unsigned long clone_flags, unsigned long usp,
+		unsigned long ustk_size,
+		struct task_struct *p, struct pt_regs *regs)
+{
+	struct pt_regs *childregs;
+
+	childregs = task_pt_regs(p);
+
+	*childregs = *regs;
+	childregs->a4 = 0;
+
+	if (usp == -1)
+		/* case of  __kernel_thread: we return to supervisor space */
+		childregs->sp = (unsigned long)(childregs + 1);
+	else
+		/* Otherwise use the given stack */
+		childregs->sp = usp;
+
+	/* Set usp/ksp */
+	p->thread.usp = childregs->sp;
+	/* switch_to uses stack to save/restore 14 callee-saved regs */
+	thread_saved_ksp(p) = (unsigned long)childregs - 8;
+	p->thread.pc = (unsigned int) ret_from_fork;
+	p->thread.wchan	= (unsigned long) ret_from_fork;
+#ifdef __DSBT__
+	{
+		unsigned long dp;
+
+		asm volatile ("mv .S2 b14,%0\n" : "=b"(dp));
+
+		thread_saved_dp(p) = dp;
+		if (usp == -1)
+			childregs->dp = dp;
+	}
+#endif
+	return 0;
+}
+
+/*
+ * c6x_execve() executes a new program.
+ */
+SYSCALL_DEFINE4(c6x_execve, const char __user *, name,
+		const char __user *const __user *, argv,
+		const char __user *const __user *, envp,
+		struct pt_regs *, regs)
+{
+	int error;
+	char *filename;
+
+	filename = getname(name);
+	error = PTR_ERR(filename);
+	if (IS_ERR(filename))
+		goto out;
+
+	error = do_execve(filename, argv, envp, regs);
+	putname(filename);
+out:
+	return error;
+}
+
+unsigned long get_wchan(struct task_struct *p)
+{
+	return p->thread.wchan;
+}
diff --git a/arch/c6x/kernel/switch_to.S b/arch/c6x/kernel/switch_to.S
new file mode 100644
index 0000000..09177ed
--- /dev/null
+++ b/arch/c6x/kernel/switch_to.S
@@ -0,0 +1,74 @@
+/*
+ *  Copyright (C) 2011 Texas Instruments Incorporated
+ *  Author: Mark Salter (msalter@redhat.com)
+ *
+ *  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/linkage.h>
+#include <asm/asm-offsets.h>
+
+#define SP	B15
+
+	/*
+	 * void __switch_to(struct thread_info *prev,
+	 *      	    struct thread_info *next,
+	 *		    struct task_struct *tsk) ;
+	 */
+ENTRY(__switch_to)
+	LDDW	.D2T2	*+B4(THREAD_B15_14),B7:B6
+ ||	MV	.L2X	A4,B5	; prev
+ ||	MV	.L1X	B4,A5	; next
+ ||	MVC	.S2	RILC,B1
+
+	STW	.D2T2	B3,*+B5(THREAD_PC)
+ ||	STDW	.D1T1	A13:A12,*+A4(THREAD_A13_12)
+ ||	MVC	.S2	ILC,B0
+
+	LDW	.D2T2	*+B4(THREAD_PC),B3
+ ||	LDDW	.D1T1	*+A5(THREAD_A13_12),A13:A12
+
+	STDW	.D1T1	A11:A10,*+A4(THREAD_A11_10)
+ ||	STDW	.D2T2	B1:B0,*+B5(THREAD_RICL_ICL)
+#ifndef __DSBT__
+ ||	MVKL	.S2	current_ksp,B1
+#endif
+
+	STDW	.D2T2	B15:B14,*+B5(THREAD_B15_14)
+ ||	STDW	.D1T1	A15:A14,*+A4(THREAD_A15_14)
+#ifndef __DSBT__
+ ||	MVKH	.S2	current_ksp,B1
+#endif
+
+	;; Switch to next SP
+	MV	.S2	B7,SP
+#ifdef __DSBT__
+ ||	STW	.D2T2	B7,*+B14(current_ksp)
+#else
+ ||	STW	.D2T2	B7,*B1
+ ||	MV	.L2	B6,B14
+#endif
+ ||	LDDW	.D1T1	*+A5(THREAD_RICL_ICL),A1:A0
+
+	STDW	.D2T2	B11:B10,*+B5(THREAD_B11_10)
+ ||	LDDW	.D1T1	*+A5(THREAD_A15_14),A15:A14
+
+	STDW	.D2T2	B13:B12,*+B5(THREAD_B13_12)
+ ||	LDDW	.D1T1	*+A5(THREAD_A11_10),A11:A10
+
+	B	.S2	B3		; return in next E1
+ ||	LDDW	.D2T2	*+B4(THREAD_B13_12),B13:B12
+
+	LDDW	.D2T2	*+B4(THREAD_B11_10),B11:B10
+	NOP
+
+	MV	.L2X	A0,B0
+ ||	MV	.S1	A6,A4
+
+	MVC	.S2	B0,ILC
+ ||	MV	.L2X	A1,B1
+
+	MVC	.S2	B1,RILC
+ENDPROC(__switch_to)