metag: IRQ handling

Add core IRQ handling for metag. The code in irq.c exposes the TBX
signal numbers as Linux IRQs.

Signed-off-by: James Hogan <james.hogan@imgtec.com>

3 files changed, 444 insertions, 0 deletions

diff --git a/arch/metag/include/asm/irq.h b/arch/metag/include/asm/irq.h
new file mode 100644
index 000000000000..be0c8f3c5a5d
--- /dev/null
+++ b/arch/metag/include/asm/irq.h
@@ -0,0 +1,32 @@
+#ifndef __ASM_METAG_IRQ_H
+#define __ASM_METAG_IRQ_H
+
+#ifdef CONFIG_4KSTACKS
+extern void irq_ctx_init(int cpu);
+extern void irq_ctx_exit(int cpu);
+# define __ARCH_HAS_DO_SOFTIRQ
+#else
+# define irq_ctx_init(cpu) do { } while (0)
+# define irq_ctx_exit(cpu) do { } while (0)
+#endif
+
+void tbi_startup_interrupt(int);
+void tbi_shutdown_interrupt(int);
+
+struct pt_regs;
+
+int tbisig_map(unsigned int hw);
+extern void do_IRQ(int irq, struct pt_regs *regs);
+
+#ifdef CONFIG_METAG_SUSPEND_MEM
+int traps_save_context(void);
+int traps_restore_context(void);
+#endif
+
+#include <asm-generic/irq.h>
+
+#ifdef CONFIG_HOTPLUG_CPU
+extern void migrate_irqs(void);
+#endif
+
+#endif /* __ASM_METAG_IRQ_H */
diff --git a/arch/metag/include/asm/irqflags.h b/arch/metag/include/asm/irqflags.h
new file mode 100644
index 000000000000..cba5e135bc9a
--- /dev/null
+++ b/arch/metag/include/asm/irqflags.h
@@ -0,0 +1,94 @@
+/*
+ * IRQ flags handling
+ *
+ * This file gets included from lowlevel asm headers too, to provide
+ * wrapped versions of the local_irq_*() APIs, based on the
+ * raw_local_irq_*() functions from the lowlevel headers.
+ */
+#ifndef _ASM_IRQFLAGS_H
+#define _ASM_IRQFLAGS_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm/core_reg.h>
+#include <asm/metag_regs.h>
+
+#define INTS_OFF_MASK TXSTATI_BGNDHALT_BIT
+
+#ifdef CONFIG_SMP
+extern unsigned int get_trigger_mask(void);
+#else
+
+extern unsigned int global_trigger_mask;
+
+static inline unsigned int get_trigger_mask(void)
+{
+        return global_trigger_mask;
+}
+#endif
+
+static inline unsigned long arch_local_save_flags(void)
+{
+        return __core_reg_get(TXMASKI);
+}
+
+static inline int arch_irqs_disabled_flags(unsigned long flags)
+{
+        return (flags & ~INTS_OFF_MASK) == 0;
+}
+
+static inline int arch_irqs_disabled(void)
+{
+        unsigned long flags = arch_local_save_flags();
+
+        return arch_irqs_disabled_flags(flags);
+}
+
+static inline unsigned long __irqs_disabled(void)
+{
+        /*
+         * We shouldn't enable exceptions if they are not already
+         * enabled. This is required for chancalls to work correctly.
+         */
+        return arch_local_save_flags() & INTS_OFF_MASK;
+}
+
+/*
+ * For spinlocks, etc:
+ */
+static inline unsigned long arch_local_irq_save(void)
+{
+        unsigned long flags = __irqs_disabled();
+
+        asm volatile("SWAP %0,TXMASKI\n" : "=r" (flags) : "0" (flags)
+                     : "memory");
+
+        return flags;
+}
+
+static inline void arch_local_irq_restore(unsigned long flags)
+{
+        asm volatile("MOV TXMASKI,%0\n" : : "r" (flags) : "memory");
+}
+
+static inline void arch_local_irq_disable(void)
+{
+        unsigned long flags = __irqs_disabled();
+
+        asm volatile("MOV TXMASKI,%0\n" : : "r" (flags) : "memory");
+}
+
+static inline void arch_local_irq_enable(void)
+{
+#ifdef CONFIG_SMP
+        preempt_disable();
+        arch_local_irq_restore(get_trigger_mask());
+        preempt_enable_no_resched();
+#else
+        arch_local_irq_restore(get_trigger_mask());
+#endif
+}
+
+#endif /* (__ASSEMBLY__) */
+
+#endif /* !(_ASM_IRQFLAGS_H) */
diff --git a/arch/metag/kernel/irq.c b/arch/metag/kernel/irq.c
new file mode 100644
index 000000000000..7c043491e1e3
--- /dev/null
+++ b/arch/metag/kernel/irq.c
@@ -0,0 +1,318 @@
+/*
+ * Linux/Meta general interrupt handling code
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/irqdomain.h>
+#include <linux/ratelimit.h>
+
+#include <asm/core_reg.h>
+#include <asm/mach/arch.h>
+#include <asm/uaccess.h>
+
+#ifdef CONFIG_4KSTACKS
+union irq_ctx {
+        struct thread_info      tinfo;
+        u32                     stack[THREAD_SIZE/sizeof(u32)];
+};
+
+static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
+static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
+#endif
+
+struct irq_domain *root_domain;
+
+static unsigned int startup_meta_irq(struct irq_data *data)
+{
+        tbi_startup_interrupt(data->hwirq);
+        return 0;
+}
+
+static void shutdown_meta_irq(struct irq_data *data)
+{
+        tbi_shutdown_interrupt(data->hwirq);
+}
+
+void do_IRQ(int irq, struct pt_regs *regs)
+{
+        struct pt_regs *old_regs = set_irq_regs(regs);
+#ifdef CONFIG_4KSTACKS
+        struct irq_desc *desc;
+        union irq_ctx *curctx, *irqctx;
+        u32 *isp;
+#endif
+
+        irq_enter();
+
+        irq = irq_linear_revmap(root_domain, irq);
+
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+        /* Debugging check for stack overflow: is there less than 1KB free? */
+        {
+                unsigned long sp;
+
+                sp = __core_reg_get(A0StP);
+                sp &= THREAD_SIZE - 1;
+
+                if (unlikely(sp > (THREAD_SIZE - 1024)))
+                        pr_err("Stack overflow in do_IRQ: %ld\n", sp);
+        }
+#endif
+
+
+#ifdef CONFIG_4KSTACKS
+        curctx = (union irq_ctx *) current_thread_info();
+        irqctx = hardirq_ctx[smp_processor_id()];
+
+        /*
+         * this is where we switch to the IRQ stack. However, if we are
+         * already using the IRQ stack (because we interrupted a hardirq
+         * handler) we can't do that and just have to keep using the
+         * current stack (which is the irq stack already after all)
+         */
+        if (curctx != irqctx) {
+                /* build the stack frame on the IRQ stack */
+                isp = (u32 *) ((char *)irqctx + sizeof(struct thread_info));
+                irqctx->tinfo.task = curctx->tinfo.task;
+
+                /*
+                 * Copy the softirq bits in preempt_count so that the
+                 * softirq checks work in the hardirq context.
+                 */
+                irqctx->tinfo.preempt_count =
+                        (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
+                        (curctx->tinfo.preempt_count & SOFTIRQ_MASK);
+
+                desc = irq_to_desc(irq);
+
+                asm volatile (
+                        "MOV   D0.5,%0\n"
+                        "MOV   D1Ar1,%1\n"
+                        "MOV   D1RtP,%2\n"
+                        "MOV   D0Ar2,%3\n"
+                        "SWAP  A0StP,D0.5\n"
+                        "SWAP  PC,D1RtP\n"
+                        "MOV   A0StP,D0.5\n"
+                        :
+                        : "r" (isp), "r" (irq), "r" (desc->handle_irq),
+                          "r" (desc)
+                        : "memory", "cc", "D1Ar1", "D0Ar2", "D1Ar3", "D0Ar4",
+                          "D1Ar5", "D0Ar6", "D0Re0", "D1Re0", "D0.4", "D1RtP",
+                          "D0.5"
+                        );
+        } else
+#endif
+                generic_handle_irq(irq);
+
+        irq_exit();
+
+        set_irq_regs(old_regs);
+}
+
+#ifdef CONFIG_4KSTACKS
+
+static char softirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
+
+static char hardirq_stack[NR_CPUS * THREAD_SIZE] __page_aligned_bss;
+
+/*
+ * allocate per-cpu stacks for hardirq and for softirq processing
+ */
+void irq_ctx_init(int cpu)
+{
+        union irq_ctx *irqctx;
+
+        if (hardirq_ctx[cpu])
+                return;
+
+        irqctx = (union irq_ctx *) &hardirq_stack[cpu * THREAD_SIZE];
+        irqctx->tinfo.task              = NULL;
+        irqctx->tinfo.exec_domain       = NULL;
+        irqctx->tinfo.cpu               = cpu;
+        irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
+        irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
+
+        hardirq_ctx[cpu] = irqctx;
+
+        irqctx = (union irq_ctx *) &softirq_stack[cpu * THREAD_SIZE];
+        irqctx->tinfo.task              = NULL;
+        irqctx->tinfo.exec_domain       = NULL;
+        irqctx->tinfo.cpu               = cpu;
+        irqctx->tinfo.preempt_count     = 0;
+        irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
+
+        softirq_ctx[cpu] = irqctx;
+
+        pr_info("CPU %u irqstacks, hard=%p soft=%p\n",
+                cpu, hardirq_ctx[cpu], softirq_ctx[cpu]);
+}
+
+void irq_ctx_exit(int cpu)
+{
+        hardirq_ctx[smp_processor_id()] = NULL;
+}
+
+extern asmlinkage void __do_softirq(void);
+
+asmlinkage void do_softirq(void)
+{
+        unsigned long flags;
+        struct thread_info *curctx;
+        union irq_ctx *irqctx;
+        u32 *isp;
+
+        if (in_interrupt())
+                return;
+
+        local_irq_save(flags);
+
+        if (local_softirq_pending()) {
+                curctx = current_thread_info();
+                irqctx = softirq_ctx[smp_processor_id()];
+                irqctx->tinfo.task = curctx->task;
+
+                /* build the stack frame on the softirq stack */
+                isp = (u32 *) ((char *)irqctx + sizeof(struct thread_info));
+
+                asm volatile (
+                        "MOV   D0.5,%0\n"
+                        "SWAP  A0StP,D0.5\n"
+                        "CALLR D1RtP,___do_softirq\n"
+                        "MOV   A0StP,D0.5\n"
+                        :
+                        : "r" (isp)
+                        : "memory", "cc", "D1Ar1", "D0Ar2", "D1Ar3", "D0Ar4",
+                          "D1Ar5", "D0Ar6", "D0Re0", "D1Re0", "D0.4", "D1RtP",
+                          "D0.5"
+                        );
+                /*
+                 * Shouldn't happen, we returned above if in_interrupt():
+                 */
+                WARN_ON_ONCE(softirq_count());
+        }
+
+        local_irq_restore(flags);
+}
+#endif
+
+static struct irq_chip meta_irq_type = {
+        .name = "META-IRQ",
+        .irq_startup = startup_meta_irq,
+        .irq_shutdown = shutdown_meta_irq,
+};
+
+/**
+ * tbisig_map() - Map a TBI signal number to a virtual IRQ number.
+ * @hw:         Number of the TBI signal. Must be in range.
+ *
+ * Returns:     The virtual IRQ number of the TBI signal number IRQ specified by
+ *              @hw.
+ */
+int tbisig_map(unsigned int hw)
+{
+        return irq_create_mapping(root_domain, hw);
+}
+
+/**
+ * metag_tbisig_map() - map a tbi signal to a Linux virtual IRQ number
+ * @d:          root irq domain
+ * @irq:        virtual irq number
+ * @hw:         hardware irq number (TBI signal number)
+ *
+ * This sets up a virtual irq for a specified TBI signal number.
+ */
+static int metag_tbisig_map(struct irq_domain *d, unsigned int irq,
+                            irq_hw_number_t hw)
+{
+#ifdef CONFIG_SMP
+        irq_set_chip_and_handler(irq, &meta_irq_type, handle_percpu_irq);
+#else
+        irq_set_chip_and_handler(irq, &meta_irq_type, handle_simple_irq);
+#endif
+        return 0;
+}
+
+static const struct irq_domain_ops metag_tbisig_domain_ops = {
+        .map = metag_tbisig_map,
+};
+
+/*
+ * void init_IRQ(void)
+ *
+ * Parameters:  None
+ *
+ * Returns:     Nothing
+ *
+ * This function should be called during kernel startup to initialize
+ * the IRQ handling routines.
+ */
+void __init init_IRQ(void)
+{
+        root_domain = irq_domain_add_linear(NULL, 32,
+                                            &metag_tbisig_domain_ops, NULL);
+        if (unlikely(!root_domain))
+                panic("init_IRQ: cannot add root IRQ domain");
+
+        irq_ctx_init(smp_processor_id());
+
+        if (machine_desc->init_irq)
+                machine_desc->init_irq();
+}
+
+int __init arch_probe_nr_irqs(void)
+{
+        if (machine_desc->nr_irqs)
+                nr_irqs = machine_desc->nr_irqs;
+        return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void route_irq(struct irq_data *data, unsigned int irq, unsigned int cpu)
+{
+        struct irq_desc *desc = irq_to_desc(irq);
+        struct irq_chip *chip = irq_data_get_irq_chip(data);
+
+        raw_spin_lock_irq(&desc->lock);
+        if (chip->irq_set_affinity)
+                chip->irq_set_affinity(data, cpumask_of(cpu), false);
+        raw_spin_unlock_irq(&desc->lock);
+}
+
+/*
+ * The CPU has been marked offline.  Migrate IRQs off this CPU.  If
+ * the affinity settings do not allow other CPUs, force them onto any
+ * available CPU.
+ */
+void migrate_irqs(void)
+{
+        unsigned int i, cpu = smp_processor_id();
+        struct irq_desc *desc;
+
+        for_each_irq_desc(i, desc) {
+                struct irq_data *data = irq_desc_get_irq_data(desc);
+                unsigned int newcpu;
+
+                if (irqd_is_per_cpu(data))
+                        continue;
+
+                if (!cpumask_test_cpu(cpu, data->affinity))
+                        continue;
+
+                newcpu = cpumask_any_and(data->affinity, cpu_online_mask);
+
+                if (newcpu >= nr_cpu_ids) {
+                        pr_info_ratelimited("IRQ%u no longer affine to CPU%u\n",
+                                            i, cpu);
+
+                        cpumask_setall(data->affinity);
+                        newcpu = cpumask_any_and(data->affinity,
+                                                 cpu_online_mask);
+                }
+
+                route_irq(data, i, newcpu);
+        }
+}
+#endif /* CONFIG_HOTPLUG_CPU */