ams-delta-fiq.c

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/*
 *  Amstrad E3 FIQ handling
 *
 *  Copyright (C) 2009 Janusz Krzysztofik
 *  Copyright (c) 2006 Matt Callow
 *  Copyright (c) 2004 Amstrad Plc
 *  Copyright (C) 2001 RidgeRun, Inc.
 *
 * Parts of this code are taken from linux/arch/arm/mach-omap/irq.c
 * in the MontaVista 2.4 kernel (and the Amstrad changes therein)
 *
 * 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/gpio.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/io.h>

#include <mach/board-ams-delta.h>

#include <asm/fiq.h>

#include <mach/ams-delta-fiq.h>

static struct fiq_handler fh = {
    .name   = "ams-delta-fiq"
};

/*
 * This buffer is shared between FIQ and IRQ contexts.
 * The FIQ and IRQ isrs can both read and write it.
 * It is structured as a header section several 32bit slots,
 * followed by the circular buffer where the FIQ isr stores
 * keystrokes received from the qwerty keyboard.
 * See ams-delta-fiq.h for details of offsets.
 */
unsigned int fiq_buffer[1024];
EXPORT_SYMBOL(fiq_buffer);

static unsigned int irq_counter[16];

static irqreturn_t deferred_fiq(int irq, void *dev_id)
{
    struct irq_desc *irq_desc;
    struct irq_chip *irq_chip = NULL;
    int gpio, irq_num, fiq_count;

    irq_desc = irq_to_desc(gpio_to_irq(AMS_DELTA_GPIO_PIN_KEYBRD_CLK));
    if (irq_desc)
        irq_chip = irq_desc->irq_data.chip;

    /*
     * For each handled GPIO interrupt, keep calling its interrupt handler
     * until the IRQ counter catches the FIQ incremented interrupt counter.
     */
    for (gpio = AMS_DELTA_GPIO_PIN_KEYBRD_CLK;
            gpio <= AMS_DELTA_GPIO_PIN_HOOK_SWITCH; gpio++) {
        irq_num = gpio_to_irq(gpio);
        fiq_count = fiq_buffer[FIQ_CNT_INT_00 + gpio];

        while (irq_counter[gpio] < fiq_count) {
            if (gpio != AMS_DELTA_GPIO_PIN_KEYBRD_CLK) {
                struct irq_data *d = irq_get_irq_data(irq_num);

                /*
                 * It looks like handle_edge_irq() that
                 * OMAP GPIO edge interrupts default to,
                 * expects interrupt already unmasked.
                 */
                if (irq_chip && irq_chip->irq_unmask)
                    irq_chip->irq_unmask(d);
            }
            generic_handle_irq(irq_num);

            irq_counter[gpio]++;
        }
    }
    return IRQ_HANDLED;
}

void __init ams_delta_init_fiq(void)
{
    void *fiqhandler_start;
    unsigned int fiqhandler_length;
    struct pt_regs FIQ_regs;
    unsigned long val, offset;
    int i, retval;

    fiqhandler_start = &qwerty_fiqin_start;
    fiqhandler_length = &qwerty_fiqin_end - &qwerty_fiqin_start;
    pr_info("Installing fiq handler from %p, length 0x%x\n",
            fiqhandler_start, fiqhandler_length);

    retval = claim_fiq(&fh);
    if (retval) {
        pr_err("ams_delta_init_fiq(): couldn't claim FIQ, ret=%d\n",
                retval);
        return;
    }

    retval = request_irq(INT_DEFERRED_FIQ, deferred_fiq,
            IRQ_TYPE_EDGE_RISING, "deferred_fiq", NULL);
    if (retval < 0) {
        pr_err("Failed to get deferred_fiq IRQ, ret=%d\n", retval);
        release_fiq(&fh);
        return;
    }
    /*
     * Since no set_type() method is provided by OMAP irq chip,
     * switch to edge triggered interrupt type manually.
     */
    offset = IRQ_ILR0_REG_OFFSET + INT_DEFERRED_FIQ * 0x4;
    val = omap_readl(DEFERRED_FIQ_IH_BASE + offset) & ~(1 << 1);
    omap_writel(val, DEFERRED_FIQ_IH_BASE + offset);

    set_fiq_handler(fiqhandler_start, fiqhandler_length);

    /*
     * Initialise the buffer which is shared
     * between FIQ mode and IRQ mode
     */
    fiq_buffer[FIQ_GPIO_INT_MASK]   = 0;
    fiq_buffer[FIQ_MASK]        = 0;
    fiq_buffer[FIQ_STATE]       = 0;
    fiq_buffer[FIQ_KEY]     = 0;
    fiq_buffer[FIQ_KEYS_CNT]    = 0;
    fiq_buffer[FIQ_KEYS_HICNT]  = 0;
    fiq_buffer[FIQ_TAIL_OFFSET] = 0;
    fiq_buffer[FIQ_HEAD_OFFSET] = 0;
    fiq_buffer[FIQ_BUF_LEN]     = 256;
    fiq_buffer[FIQ_MISSED_KEYS] = 0;
    fiq_buffer[FIQ_BUFFER_START]    =
            (unsigned int) &fiq_buffer[FIQ_CIRC_BUFF];

    for (i = FIQ_CNT_INT_00; i <= FIQ_CNT_INT_15; i++)
        fiq_buffer[i] = 0;

    /*
     * FIQ mode r9 always points to the fiq_buffer, becauses the FIQ isr
     * will run in an unpredictable context. The fiq_buffer is the FIQ isr's
     * only means of communication with the IRQ level and other kernel
     * context code.
     */
    FIQ_regs.ARM_r9 = (unsigned int)fiq_buffer;
    set_fiq_regs(&FIQ_regs);

    pr_info("request_fiq(): fiq_buffer = %p\n", fiq_buffer);

    /*
     * Redirect GPIO interrupts to FIQ
     */
    offset = IRQ_ILR0_REG_OFFSET + INT_GPIO_BANK1 * 0x4;
    val = omap_readl(OMAP_IH1_BASE + offset) | 1;
    omap_writel(val, OMAP_IH1_BASE + offset);
}