nios2: Process management

This patch adds support for thread creation and context switching.

Signed-off-by: Ley Foon Tan <lftan@altera.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/arch/nios2/mm/mmu_context.c b/arch/nios2/mm/mmu_context.c
new file mode 100644
index 000000000000..45d6b9c58d67
--- /dev/null
+++ b/arch/nios2/mm/mmu_context.c
@@ -0,0 +1,116 @@
+/*
+ * MMU context handling.
+ *
+ * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009 Wind River Systems Inc
+ *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/mm.h>
+
+#include <asm/cpuinfo.h>
+#include <asm/mmu_context.h>
+#include <asm/tlb.h>
+
+/* The pids position and mask in context */
+#define PID_SHIFT       0
+#define PID_BITS        (cpuinfo.tlb_pid_num_bits)
+#define PID_MASK        ((1UL << PID_BITS) - 1)
+
+/* The versions position and mask in context */
+#define VERSION_BITS    (32 - PID_BITS)
+#define VERSION_SHIFT   (PID_SHIFT + PID_BITS)
+#define VERSION_MASK    ((1UL << VERSION_BITS) - 1)
+
+/* Return the version part of a context */
+#define CTX_VERSION(c)  (((c) >> VERSION_SHIFT) & VERSION_MASK)
+
+/* Return the pid part of a context */
+#define CTX_PID(c)      (((c) >> PID_SHIFT) & PID_MASK)
+
+/* Value of the first context (version 1, pid 0) */
+#define FIRST_CTX       ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
+
+static mm_context_t next_mmu_context;
+
+/*
+ * Initialize MMU context management stuff.
+ */
+void __init mmu_context_init(void)
+{
+        /* We need to set this here because the value depends on runtime data
+         * from cpuinfo */
+        next_mmu_context = FIRST_CTX;
+}
+
+/*
+ * Set new context (pid), keep way
+ */
+static void set_context(mm_context_t context)
+{
+        set_mmu_pid(CTX_PID(context));
+}
+
+static mm_context_t get_new_context(void)
+{
+        /* Return the next pid */
+        next_mmu_context += (1UL << PID_SHIFT);
+
+        /* If the pid field wraps around we increase the version and
+         * flush the tlb */
+        if (unlikely(CTX_PID(next_mmu_context) == 0)) {
+                /* Version is incremented since the pid increment above
+                 * overflows info version */
+                flush_cache_all();
+                flush_tlb_all();
+        }
+
+        /* If the version wraps we start over with the first generation, we do
+         * not need to flush the tlb here since it's always done above */
+        if (unlikely(CTX_VERSION(next_mmu_context) == 0))
+                next_mmu_context = FIRST_CTX;
+
+        return next_mmu_context;
+}
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+               struct task_struct *tsk)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+
+        /* If the process context we are swapping in has a different context
+         * generation then we have it should get a new generation/pid */
+        if (unlikely(CTX_VERSION(next->context) !=
+                CTX_VERSION(next_mmu_context)))
+                next->context = get_new_context();
+
+        /* Save the current pgd so the fast tlb handler can find it */
+        pgd_current = next->pgd;
+
+        /* Set the current context */
+        set_context(next->context);
+
+        local_irq_restore(flags);
+}
+
+/*
+ * After we have set current->mm to a new value, this activates
+ * the context for the new mm so we see the new mappings.
+ */
+void activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+        next->context = get_new_context();
+        set_context(next->context);
+        pgd_current = next->pgd;
+}
+
+unsigned long get_pid_from_context(mm_context_t *context)
+{
+        return CTX_PID((*context));
+}