// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Aspeed AST24XX, AST25XX, and AST26XX SCU Interrupt Controller
 * Copyright 2019 IBM Corporation
 *
 * Eddie James <eajames@linux.ibm.com>
 */

#include <linux/bitops.h>
#include <linux/irq.h>
#include <linux/irqchip.h>
#include <linux/irqchip/chained_irq.h>
#include <linux/irqdomain.h>
#include <linux/mfd/syscon.h>
#include <linux/of_irq.h>
#include <linux/regmap.h>

#define ASPEED_SCU_IC_REG               0x018
#define ASPEED_SCU_IC_SHIFT             0
#define ASPEED_SCU_IC_ENABLE            GENMASK(6, ASPEED_SCU_IC_SHIFT)
#define ASPEED_SCU_IC_NUM_IRQS          7
#define ASPEED_SCU_IC_STATUS_SHIFT      16

#define ASPEED_AST2600_SCU_IC0_REG      0x560
#define ASPEED_AST2600_SCU_IC0_SHIFT    0
#define ASPEED_AST2600_SCU_IC0_ENABLE   \
        GENMASK(5, ASPEED_AST2600_SCU_IC0_SHIFT)
#define ASPEED_AST2600_SCU_IC0_NUM_IRQS 6

#define ASPEED_AST2600_SCU_IC1_REG      0x570
#define ASPEED_AST2600_SCU_IC1_SHIFT    4
#define ASPEED_AST2600_SCU_IC1_ENABLE   \
        GENMASK(5, ASPEED_AST2600_SCU_IC1_SHIFT)
#define ASPEED_AST2600_SCU_IC1_NUM_IRQS 2

struct aspeed_scu_ic {
        unsigned long irq_enable;
        unsigned long irq_shift;
        unsigned int num_irqs;
        unsigned int reg;
        struct regmap *scu;
        struct irq_domain *irq_domain;
};

static void aspeed_scu_ic_irq_handler(struct irq_desc *desc)
{
        unsigned int sts;
        unsigned long bit;
        unsigned long enabled;
        unsigned long max;
        unsigned long status;
        struct aspeed_scu_ic *scu_ic = irq_desc_get_handler_data(desc);
        struct irq_chip *chip = irq_desc_get_chip(desc);
        unsigned int mask = scu_ic->irq_enable << ASPEED_SCU_IC_STATUS_SHIFT;

        chained_irq_enter(chip, desc);

        /*
         * The SCU IC has just one register to control its operation and read
         * status. The interrupt enable bits occupy the lower 16 bits of the
         * register, while the interrupt status bits occupy the upper 16 bits.
         * The status bit for a given interrupt is always 16 bits shifted from
         * the enable bit for the same interrupt.
         * Therefore, perform the IRQ operations in the enable bit space by
         * shifting the status down to get the mapping and then back up to
         * clear the bit.
         */
        regmap_read(scu_ic->scu, scu_ic->reg, &sts);
        enabled = sts & scu_ic->irq_enable;
        status = (sts >> ASPEED_SCU_IC_STATUS_SHIFT) & enabled;

        bit = scu_ic->irq_shift;
        max = scu_ic->num_irqs + bit;

        for_each_set_bit_from(bit, &status, max) {
                generic_handle_domain_irq(scu_ic->irq_domain,
                                          bit - scu_ic->irq_shift);

                regmap_update_bits(scu_ic->scu, scu_ic->reg, mask,
                                   BIT(bit + ASPEED_SCU_IC_STATUS_SHIFT));
        }

        chained_irq_exit(chip, desc);
}

static void aspeed_scu_ic_irq_mask(struct irq_data *data)
{
        struct aspeed_scu_ic *scu_ic = irq_data_get_irq_chip_data(data);
        unsigned int mask = BIT(data->hwirq + scu_ic->irq_shift) |
                (scu_ic->irq_enable << ASPEED_SCU_IC_STATUS_SHIFT);

        /*
         * Status bits are cleared by writing 1. In order to prevent the mask
         * operation from clearing the status bits, they should be under the
         * mask and written with 0.
         */
        regmap_update_bits(scu_ic->scu, scu_ic->reg, mask, 0);
}

static void aspeed_scu_ic_irq_unmask(struct irq_data *data)
{
        struct aspeed_scu_ic *scu_ic = irq_data_get_irq_chip_data(data);
        unsigned int bit = BIT(data->hwirq + scu_ic->irq_shift);
        unsigned int mask = bit |
                (scu_ic->irq_enable << ASPEED_SCU_IC_STATUS_SHIFT);

        /*
         * Status bits are cleared by writing 1. In order to prevent the unmask
         * operation from clearing the status bits, they should be under the
         * mask and written with 0.
         */
        regmap_update_bits(scu_ic->scu, scu_ic->reg, mask, bit);
}

static int aspeed_scu_ic_irq_set_affinity(struct irq_data *data,
                                          const struct cpumask *dest,
                                          bool force)
{
        return -EINVAL;
}

static struct irq_chip aspeed_scu_ic_chip = {
        .name                   = "aspeed-scu-ic",
        .irq_mask               = aspeed_scu_ic_irq_mask,
        .irq_unmask             = aspeed_scu_ic_irq_unmask,
        .irq_set_affinity       = aspeed_scu_ic_irq_set_affinity,
};

static int aspeed_scu_ic_map(struct irq_domain *domain, unsigned int irq,
                             irq_hw_number_t hwirq)
{
        irq_set_chip_and_handler(irq, &aspeed_scu_ic_chip, handle_level_irq);
        irq_set_chip_data(irq, domain->host_data);

        return 0;
}

static const struct irq_domain_ops aspeed_scu_ic_domain_ops = {
        .map = aspeed_scu_ic_map,
};

static int aspeed_scu_ic_of_init_common(struct aspeed_scu_ic *scu_ic,
                                        struct device_node *node)
{
        int irq;
        int rc = 0;

        if (!node->parent) {
                rc = -ENODEV;
                goto err;
        }

        scu_ic->scu = syscon_node_to_regmap(node->parent);
        if (IS_ERR(scu_ic->scu)) {
                rc = PTR_ERR(scu_ic->scu);
                goto err;
        }

        irq = irq_of_parse_and_map(node, 0);
        if (irq < 0) {
                rc = irq;
                goto err;
        }

        scu_ic->irq_domain = irq_domain_add_linear(node, scu_ic->num_irqs,
                                                   &aspeed_scu_ic_domain_ops,
                                                   scu_ic);
        if (!scu_ic->irq_domain) {
                rc = -ENOMEM;
                goto err;
        }

        irq_set_chained_handler_and_data(irq, aspeed_scu_ic_irq_handler,
                                         scu_ic);

        return 0;

err:
        kfree(scu_ic);

        return rc;
}

static int __init aspeed_scu_ic_of_init(struct device_node *node,
                                        struct device_node *parent)
{
        struct aspeed_scu_ic *scu_ic = kzalloc(sizeof(*scu_ic), GFP_KERNEL);

        if (!scu_ic)
                return -ENOMEM;

        scu_ic->irq_enable = ASPEED_SCU_IC_ENABLE;
        scu_ic->irq_shift = ASPEED_SCU_IC_SHIFT;
        scu_ic->num_irqs = ASPEED_SCU_IC_NUM_IRQS;
        scu_ic->reg = ASPEED_SCU_IC_REG;

        return aspeed_scu_ic_of_init_common(scu_ic, node);
}

static int __init aspeed_ast2600_scu_ic0_of_init(struct device_node *node,
                                                 struct device_node *parent)
{
        struct aspeed_scu_ic *scu_ic = kzalloc(sizeof(*scu_ic), GFP_KERNEL);

        if (!scu_ic)
                return -ENOMEM;

        scu_ic->irq_enable = ASPEED_AST2600_SCU_IC0_ENABLE;
        scu_ic->irq_shift = ASPEED_AST2600_SCU_IC0_SHIFT;
        scu_ic->num_irqs = ASPEED_AST2600_SCU_IC0_NUM_IRQS;
        scu_ic->reg = ASPEED_AST2600_SCU_IC0_REG;

        return aspeed_scu_ic_of_init_common(scu_ic, node);
}

static int __init aspeed_ast2600_scu_ic1_of_init(struct device_node *node,
                                                 struct device_node *parent)
{
        struct aspeed_scu_ic *scu_ic = kzalloc(sizeof(*scu_ic), GFP_KERNEL);

        if (!scu_ic)
                return -ENOMEM;

        scu_ic->irq_enable = ASPEED_AST2600_SCU_IC1_ENABLE;
        scu_ic->irq_shift = ASPEED_AST2600_SCU_IC1_SHIFT;
        scu_ic->num_irqs = ASPEED_AST2600_SCU_IC1_NUM_IRQS;
        scu_ic->reg = ASPEED_AST2600_SCU_IC1_REG;

        return aspeed_scu_ic_of_init_common(scu_ic, node);
}

IRQCHIP_DECLARE(ast2400_scu_ic, "aspeed,ast2400-scu-ic", aspeed_scu_ic_of_init);
IRQCHIP_DECLARE(ast2500_scu_ic, "aspeed,ast2500-scu-ic", aspeed_scu_ic_of_init);
IRQCHIP_DECLARE(ast2600_scu_ic0, "aspeed,ast2600-scu-ic0",
                aspeed_ast2600_scu_ic0_of_init);
IRQCHIP_DECLARE(ast2600_scu_ic1, "aspeed,ast2600-scu-ic1",
                aspeed_ast2600_scu_ic1_of_init);