/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel_stat.h>
#include <linux/uaccess.h>
#include <hv/drv_pcie_rc_intf.h>
#include <arch/spr_def.h>
#include <asm/traps.h>

/* Bit-flag stored in irq_desc->chip_data to indicate HW-cleared irqs. */
#define IS_HW_CLEARED 1

/*
 * The set of interrupts we enable for arch_local_irq_enable().
 * This is initialized to have just a single interrupt that the kernel
 * doesn't actually use as a sentinel.  During kernel init,
 * interrupts are added as the kernel gets prepared to support them.
 * NOTE: we could probably initialize them all statically up front.
 */
DEFINE_PER_CPU(unsigned long long, interrupts_enabled_mask) =
  INITIAL_INTERRUPTS_ENABLED;
EXPORT_PER_CPU_SYMBOL(interrupts_enabled_mask);

/* Define per-tile device interrupt statistics state. */
DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_internodealigned_in_smp;
EXPORT_PER_CPU_SYMBOL(irq_stat);

/*
 * Define per-tile irq disable mask; the hardware/HV only has a single
 * mask that we use to implement both masking and disabling.
 */
static DEFINE_PER_CPU(unsigned long, irq_disable_mask)
	____cacheline_internodealigned_in_smp;

/*
 * Per-tile IRQ nesting depth.  Used to make sure we enable newly
 * enabled IRQs before exiting the outermost interrupt.
 */
static DEFINE_PER_CPU(int, irq_depth);

/* State for allocating IRQs on Gx. */
#if CHIP_HAS_IPI()
static unsigned long available_irqs = ~(1UL << IRQ_RESCHEDULE);
static DEFINE_SPINLOCK(available_irqs_lock);
#endif

#if CHIP_HAS_IPI()
/* Use SPRs to manipulate device interrupts. */
#define mask_irqs(irq_mask) __insn_mtspr(SPR_IPI_MASK_SET_K, irq_mask)
#define unmask_irqs(irq_mask) __insn_mtspr(SPR_IPI_MASK_RESET_K, irq_mask)
#define clear_irqs(irq_mask) __insn_mtspr(SPR_IPI_EVENT_RESET_K, irq_mask)
#else
/* Use HV to manipulate device interrupts. */
#define mask_irqs(irq_mask) hv_disable_intr(irq_mask)
#define unmask_irqs(irq_mask) hv_enable_intr(irq_mask)
#define clear_irqs(irq_mask) hv_clear_intr(irq_mask)
#endif

/*
 * The interrupt handling path, implemented in terms of HV interrupt
 * emulation on TILE64 and TILEPro, and IPI hardware on TILE-Gx.
 * Entered with interrupts disabled.
 */
void tile_dev_intr(struct pt_regs *regs, int intnum)
{
	int depth = __get_cpu_var(irq_depth)++;
	unsigned long original_irqs;
	unsigned long remaining_irqs;
	struct pt_regs *old_regs;

#if CHIP_HAS_IPI()
	/*
	 * Pending interrupts are listed in an SPR.  We might be
	 * nested, so be sure to only handle irqs that weren't already
	 * masked by a previous interrupt.  Then, mask out the ones
	 * we're going to handle.
	 */
	unsigned long masked = __insn_mfspr(SPR_IPI_MASK_K);
	original_irqs = __insn_mfspr(SPR_IPI_EVENT_K) & ~masked;
	__insn_mtspr(SPR_IPI_MASK_SET_K, original_irqs);
#else
	/*
	 * Hypervisor performs the equivalent of the Gx code above and
	 * then puts the pending interrupt mask into a system save reg
	 * for us to find.
	 */
	original_irqs = __insn_mfspr(SPR_SYSTEM_SAVE_K_3);
#endif
	remaining_irqs = original_irqs;

	/* Track time spent here in an interrupt context. */
	old_regs = set_irq_regs(regs);
	irq_enter();

#ifdef CONFIG_DEBUG_STACKOVERFLOW
	/* Debugging check for stack overflow: less than 1/8th stack free? */
	{
		long sp = stack_pointer - (long) current_thread_info();
		if (unlikely(sp < (sizeof(struct thread_info) + STACK_WARN))) {
			pr_emerg("tile_dev_intr: "
			       "stack overflow: %ld\n",
			       sp - sizeof(struct thread_info));
			dump_stack();
		}
	}
#endif
	while (remaining_irqs) {
		unsigned long irq = __ffs(remaining_irqs);
		remaining_irqs &= ~(1UL << irq);

		/* Count device irqs; Linux IPIs are counted elsewhere. */
		if (irq != IRQ_RESCHEDULE)
			__get_cpu_var(irq_stat).irq_dev_intr_count++;

		generic_handle_irq(irq);
	}

	/*
	 * If we weren't nested, turn on all enabled interrupts,
	 * including any that were reenabled during interrupt
	 * handling.
	 */
	if (depth == 0)
		unmask_irqs(~__get_cpu_var(irq_disable_mask));

	__get_cpu_var(irq_depth)--;

	/*
	 * Track time spent against the current process again and
	 * process any softirqs if they are waiting.
	 */
	irq_exit();
	set_irq_regs(old_regs);
}


/*
 * Remove an irq from the disabled mask.  If we're in an interrupt
 * context, defer enabling the HW interrupt until we leave.
 */
static void tile_irq_chip_enable(struct irq_data *d)
{
	get_cpu_var(irq_disable_mask) &= ~(1UL << d->irq);
	if (__get_cpu_var(irq_depth) == 0)
		unmask_irqs(1UL << d->irq);
	put_cpu_var(irq_disable_mask);
}

/*
 * Add an irq to the disabled mask.  We disable the HW interrupt
 * immediately so that there's no possibility of it firing.  If we're
 * in an interrupt context, the return path is careful to avoid
 * unmasking a newly disabled interrupt.
 */
static void tile_irq_chip_disable(struct irq_data *d)
{
	get_cpu_var(irq_disable_mask) |= (1UL << d->irq);
	mask_irqs(1UL << d->irq);
	put_cpu_var(irq_disable_mask);
}

/* Mask an interrupt. */
static void tile_irq_chip_mask(struct irq_data *d)
{
	mask_irqs(1UL << d->irq);
}

/* Unmask an interrupt. */
static void tile_irq_chip_unmask(struct irq_data *d)
{
	unmask_irqs(1UL << d->irq);
}

/*
 * Clear an interrupt before processing it so that any new assertions
 * will trigger another irq.
 */
static void tile_irq_chip_ack(struct irq_data *d)
{
	if ((unsigned long)irq_data_get_irq_chip_data(d) != IS_HW_CLEARED)
		clear_irqs(1UL << d->irq);
}

/*
 * For per-cpu interrupts, we need to avoid unmasking any interrupts
 * that we disabled via disable_percpu_irq().
 */
static void tile_irq_chip_eoi(struct irq_data *d)
{
	if (!(__get_cpu_var(irq_disable_mask) & (1UL << d->irq)))
		unmask_irqs(1UL << d->irq);
}

static struct irq_chip tile_irq_chip = {
	.name = "tile_irq_chip",
	.irq_enable = tile_irq_chip_enable,
	.irq_disable = tile_irq_chip_disable,
	.irq_ack = tile_irq_chip_ack,
	.irq_eoi = tile_irq_chip_eoi,
	.irq_mask = tile_irq_chip_mask,
	.irq_unmask = tile_irq_chip_unmask,
};

void __init init_IRQ(void)
{
	ipi_init();
}

void __cpuinit setup_irq_regs(void)
{
	/* Enable interrupt delivery. */
	unmask_irqs(~0UL);
#if CHIP_HAS_IPI()
	arch_local_irq_unmask(INT_IPI_K);
#endif
}

void tile_irq_activate(unsigned int irq, int tile_irq_type)
{
	/*
	 * We use handle_level_irq() by default because the pending
	 * interrupt vector (whether modeled by the HV on TILE64 and
	 * TILEPro or implemented in hardware on TILE-Gx) has
	 * level-style semantics for each bit.  An interrupt fires
	 * whenever a bit is high, not just at edges.
	 */
	irq_flow_handler_t handle = handle_level_irq;
	if (tile_irq_type == TILE_IRQ_PERCPU)
		handle = handle_percpu_irq;
	irq_set_chip_and_handler(irq, &tile_irq_chip, handle);

	/*
	 * Flag interrupts that are hardware-cleared so that ack()
	 * won't clear them.
	 */
	if (tile_irq_type == TILE_IRQ_HW_CLEAR)
		irq_set_chip_data(irq, (void *)IS_HW_CLEARED);
}
EXPORT_SYMBOL(tile_irq_activate);


void ack_bad_irq(unsigned int irq)
{
	pr_err("unexpected IRQ trap at vector %02x\n", irq);
}

/*
 * Generic, controller-independent functions:
 */

#if CHIP_HAS_IPI()
int create_irq(void)
{
	unsigned long flags;
	int result;

	spin_lock_irqsave(&available_irqs_lock, flags);
	if (available_irqs == 0)
		result = -ENOMEM;
	else {
		result = __ffs(available_irqs);
		available_irqs &= ~(1UL << result);
		dynamic_irq_init(result);
	}
	spin_unlock_irqrestore(&available_irqs_lock, flags);

	return result;
}
EXPORT_SYMBOL(create_irq);

void destroy_irq(unsigned int irq)
{
	unsigned long flags;

	spin_lock_irqsave(&available_irqs_lock, flags);
	available_irqs |= (1UL << irq);
	dynamic_irq_cleanup(irq);
	spin_unlock_irqrestore(&available_irqs_lock, flags);
}
EXPORT_SYMBOL(destroy_irq);
#endif