Nested Interrupts in OMAPL138

/*
 * TI Common Platform Interrupt Controller (cp_intc) driver
 *
 * Author: Steve Chen <schen@mvista.com>
 * Copyright (C) 2008-2009, MontaVista Software, Inc. <source@mvista.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2. This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */

#include <linux/init.h>
#include <linux/irq.h>
#include <linux/io.h>

#include <mach/common.h>
#include <mach/cp_intc.h>

#define STACK_MAX 32

struct Stack {
    int data[STACK_MAX];
    int size;
};

struct Stack m_nestStack;

void stackInit(struct Stack *stack) {
	stack->size = 0;
}

int stackTop(struct Stack *stack) {
    if (stack->size == 0)
        return -1;

    return stack->data[stack->size-1];
}

void stackPush(struct Stack *stack, int d) {
    if (stack->size < STACK_MAX)
   	 stack->data[stack->size++] = d;
    else
        pr_warning("CP_INTC: Nest stack filled\n");
}

void stackPop(struct Stack *stack) {
    if (stack->size == 0)
   	 pr_warning("CP_INTC: Nest stack empty\n");
    else
   	 stack->size--;
}

static inline unsigned int cp_intc_read(unsigned offset)
{
	return __raw_readl(davinci_intc_base + offset);
}

static inline void cp_intc_write(unsigned long value, unsigned offset)
{
	__raw_writel(value, davinci_intc_base + offset);
}

/* Disable interrupt */
static void cp_intc_mask_irq(struct irq_data *d)
{
	/* XXX don't know why we need to disable nIRQ here... */
	cp_intc_write(1, CP_INTC_HOST_ENABLE_IDX_CLR);
	cp_intc_write(d->irq, CP_INTC_SYS_ENABLE_IDX_CLR);
	cp_intc_write(1, CP_INTC_HOST_ENABLE_IDX_SET);
}

/* Enable interrupt */
static void cp_intc_unmask_irq(struct irq_data *d)
{
	cp_intc_write(d->irq, CP_INTC_SYS_ENABLE_IDX_SET);
}

static void cp_intc_ack_irq(struct irq_data *d)
{
	cp_intc_write(d->irq, CP_INTC_SYS_STAT_IDX_CLR);
	cp_intc_unmask_irq(d);//todo ajr: added
}

static int cp_intc_set_irq_type(struct irq_data *d, unsigned int flow_type)
{
	unsigned reg		= BIT_WORD(d->irq);
	unsigned mask		= BIT_MASK(d->irq);
	unsigned polarity	= cp_intc_read(CP_INTC_SYS_POLARITY(reg));
	unsigned type		= cp_intc_read(CP_INTC_SYS_TYPE(reg));

	switch (flow_type) {
	case IRQ_TYPE_EDGE_RISING:
		polarity |= mask;
		type |= mask;
		break;
	case IRQ_TYPE_EDGE_FALLING:
		polarity &= ~mask;
		type |= mask;
		break;
	case IRQ_TYPE_LEVEL_HIGH:
		polarity |= mask;
		type &= ~mask;
		break;
	case IRQ_TYPE_LEVEL_LOW:
		polarity &= ~mask;
		type &= ~mask;
		break;
	default:
		return -EINVAL;
	}

	cp_intc_write(polarity, CP_INTC_SYS_POLARITY(reg));
	cp_intc_write(type, CP_INTC_SYS_TYPE(reg));

	return 0;
}

/*
 * Faking this allows us to to work with suspend functions of
 * generic drivers which call {enable|disable}_irq_wake for
 * wake up interrupt sources (eg RTC on DA850).
 */
static int cp_intc_set_wake(struct irq_data *d, unsigned int on)
{
	return 0;
}

static struct irq_chip cp_intc_irq_chip = {
	.name		= "cp_intc",
	.irq_ack	= cp_intc_ack_irq,
	.irq_mask	= cp_intc_mask_irq,
	.irq_unmask	= cp_intc_unmask_irq,
	.irq_set_type	= cp_intc_set_irq_type,
	.irq_set_wake	= cp_intc_set_wake,
};

static void cp_intc_set_nested_level(unsigned int irq, unsigned int level)
{
	cp_intc_write((BIT(31) | level), CP_INTC_HOST_NESTING_LEVEL(irq));
}

static int cp_intc_get_nested_level(unsigned int irq)
{
	return cp_intc_read(CP_INTC_HOST_NESTING_LEVEL(irq));
}

void cp_intc_irq_handler(unsigned int irq, struct irq_desc *desc)
{
	int currLevel;

	//1. Mask interrupt
	cp_intc_mask_irq(&desc->irq_data);

	//2. Obtain current nested level
	currLevel = cp_intc_get_nested_level(irq);

	//3. Save to the stack
	stackPush(&m_nestStack, currLevel);

	//4. Set the new level
	cp_intc_set_nested_level(irq, davinci_soc_info.intc_irq_prios[irq]);

	//5. skip for now...
	//6 - 8 handled generically
	handle_edge_irq(irq, desc);

	//9. Mask interrupt
	cp_intc_mask_irq(&desc->irq_data);

	//10. Restore priority
	currLevel = stackTop(&m_nestStack);
	stackPop(&m_nestStack);

	//11. Exit
	cp_intc_unmask_irq(&desc->irq_data);
}

void __init cp_intc_init(void)
{
	unsigned long num_irq	= davinci_soc_info.intc_irq_num;
	u8 *irq_prio		= davinci_soc_info.intc_irq_prios;
	u32 *host_map		= davinci_soc_info.intc_host_map;
	unsigned num_reg	= BITS_TO_LONGS(num_irq);
	int i;

	davinci_intc_type = DAVINCI_INTC_TYPE_CP_INTC;
	davinci_intc_base = ioremap(davinci_soc_info.intc_base, SZ_8K);
	if (WARN_ON(!davinci_intc_base))
		return;

	cp_intc_write(0, CP_INTC_GLOBAL_ENABLE);

	/* Disable all host interrupts */
	cp_intc_write(0, CP_INTC_HOST_ENABLE(0));

	/* Disable system interrupts */
	for (i = 0; i < num_reg; i++)
		cp_intc_write(~0, CP_INTC_SYS_ENABLE_CLR(i));


	cp_intc_write(0x4, CP_INTC_CTRL);
	cp_intc_write(0, CP_INTC_HOST_CTRL);

	/* Clear system interrupt status */
	for (i = 0; i < num_reg; i++)
		cp_intc_write(~0, CP_INTC_SYS_STAT_CLR(i));

	/* Enable nIRQ (what about nFIQ?) */
	cp_intc_write(1, CP_INTC_HOST_ENABLE_IDX_SET);

	/*
	 * Priority is determined by host channel: lower channel number has
	 * higher priority i.e. channel 0 has highest priority and channel 31
	 * had the lowest priority.
	 */
	num_reg = (num_irq + 3) >> 2;	/* 4 channels per register */
	if (irq_prio) {
		unsigned j, k;
		u32 val;

		for (k = i = 0; i < num_reg; i++) {
			for (val = j = 0; j < 4; j++, k++) {
				val >>= 8;
				if (k < num_irq)
					val |= irq_prio[k] << 24;
			}

			cp_intc_write(val, CP_INTC_CHAN_MAP(i));
		}
	} else	{
		/*
		 * Default everything to channel 15 if priority not specified.
		 * Note that channel 0-1 are mapped to nFIQ and channels 2-31
		 * are mapped to nIRQ.
		 */
		for (i = 0; i < num_reg; i++)
			cp_intc_write(0x0f0f0f0f, CP_INTC_CHAN_MAP(i));
	}

	if (host_map)
		for (i = 0; host_map[i] != -1; i++)
			cp_intc_write(host_map[i], CP_INTC_HOST_MAP(i));

	/* Set up genirq dispatching for cp_intc */
	for (i = 0; i < num_irq; i++) {
		irq_set_chip(i, &cp_intc_irq_chip);
		set_irq_flags(i, IRQF_VALID | IRQF_PROBE);
		irq_set_handler(i, cp_intc_irq_handler);
	}

	stackInit(&m_nestStack);
	stackPush(&m_nestStack, 31);

	/* Enable global interrupt */
	cp_intc_write(1, CP_INTC_GLOBAL_ENABLE);
}