// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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)
 */
#include <linux/gpio/consumer.h>
#include <linux/gpio/machine.h>
#include <linux/gpio/driver.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/platform_data/ams-delta-fiq.h>
#include <linux/platform_device.h>

#include <asm/fiq.h>

#include "ams-delta-fiq.h"
#include "board-ams-delta.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
 * <linux/platform_data/ams-delta-fiq.h> for details of offsets.
 */
static unsigned int fiq_buffer[1024];

static struct irq_chip *irq_chip;
static struct irq_data *irq_data[16];
static unsigned int irq_counter[16];

static const char *pin_name[16] __initconst = {
	[AMS_DELTA_GPIO_PIN_KEYBRD_DATA]	= "keybrd_data",
	[AMS_DELTA_GPIO_PIN_KEYBRD_CLK]		= "keybrd_clk",
};

static irqreturn_t deferred_fiq(int irq, void *dev_id)
{
	struct irq_data *d;
	int gpio, irq_num, fiq_count;

	/*
	 * 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++) {
		d = irq_data[gpio];
		irq_num = d->irq;
		fiq_count = fiq_buffer[FIQ_CNT_INT_00 + gpio];

		if (irq_counter[gpio] < fiq_count &&
				gpio != AMS_DELTA_GPIO_PIN_KEYBRD_CLK) {
			/*
			 * handle_simple_irq() that OMAP GPIO edge
			 * interrupts default to since commit 80ac93c27441
			 * requires interrupt already acked and unmasked.
			 */
			if (!WARN_ON_ONCE(!irq_chip->irq_unmask))
				irq_chip->irq_unmask(d);
		}
		for (; irq_counter[gpio] < fiq_count; irq_counter[gpio]++)
			generic_handle_irq(irq_num);
	}
	return IRQ_HANDLED;
}

void __init ams_delta_init_fiq(struct gpio_chip *chip,
			       struct platform_device *serio)
{
	struct gpio_desc *gpiod, *data = NULL, *clk = NULL;
	void *fiqhandler_start;
	unsigned int fiqhandler_length;
	struct pt_regs FIQ_regs;
	unsigned long val, offset;
	int i, retval;

	/* Store irq_chip location for IRQ handler use */
	irq_chip = chip->irq.chip;
	if (!irq_chip) {
		pr_err("%s: GPIO chip %s is missing IRQ function\n", __func__,
		       chip->label);
		return;
	}

	for (i = 0; i < ARRAY_SIZE(irq_data); i++) {
		gpiod = gpiochip_request_own_desc(chip, i, pin_name[i],
						  GPIO_ACTIVE_HIGH, GPIOD_IN);
		if (IS_ERR(gpiod)) {
			pr_err("%s: failed to get GPIO pin %d (%ld)\n",
			       __func__, i, PTR_ERR(gpiod));
			return;
		}
		/* Store irq_data location for IRQ handler use */
		irq_data[i] = irq_get_irq_data(gpiod_to_irq(gpiod));

		/*
		 * FIQ handler takes full control over serio data and clk GPIO
		 * pins.  Initialize them and keep requested so nobody can
		 * interfere.  Fail if any of those two couldn't be requested.
		 */
		switch (i) {
		case AMS_DELTA_GPIO_PIN_KEYBRD_DATA:
			data = gpiod;
			gpiod_direction_input(data);
			break;
		case AMS_DELTA_GPIO_PIN_KEYBRD_CLK:
			clk = gpiod;
			gpiod_direction_input(clk);
			break;
		default:
			gpiochip_free_own_desc(gpiod);
			break;
		}
	}
	if (!data || !clk)
		goto out_gpio;

	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);
		goto out_gpio;
	}

	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);
		goto out_gpio;
	}
	/*
	 * 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 - NR_IRQS_LEGACY) & 0x1f) * 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, because 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 - NR_IRQS_LEGACY) * 0x4;
	val = omap_readl(OMAP_IH1_BASE + offset) | 1;
	omap_writel(val, OMAP_IH1_BASE + offset);

	/* Initialize serio device IRQ resource and platform_data */
	serio->resource[0].start = gpiod_to_irq(clk);
	serio->resource[0].end = serio->resource[0].start;
	serio->dev.platform_data = fiq_buffer;

	/*
	 * Since FIQ handler performs handling of GPIO registers for
	 * "keybrd_clk" IRQ pin, ams_delta_serio driver used to set
	 * handle_simple_irq() as active IRQ handler for that pin to avoid
	 * bad interaction with gpio-omap driver.  This is no longer needed
	 * as handle_simple_irq() is now the default handler for OMAP GPIO
	 * edge interrupts.
	 * This comment replaces the obsolete code which has been removed
	 * from the ams_delta_serio driver and stands here only as a reminder
	 * of that dependency on gpio-omap driver behavior.
	 */

	return;

out_gpio:
	if (data)
		gpiochip_free_own_desc(data);
	if (clk)
		gpiochip_free_own_desc(clk);
}