// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
 *
 * Authors:
 *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
 *
 * Baikal-T1 AXI-bus driver
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/bitfield.h>
#include <linux/device.h>
#include <linux/atomic.h>
#include <linux/regmap.h>
#include <linux/platform_device.h>
#include <linux/mfd/syscon.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/nmi.h>
#include <linux/of.h>
#include <linux/clk.h>
#include <linux/reset.h>
#include <linux/sysfs.h>

#define BT1_AXI_WERRL                   0x110
#define BT1_AXI_WERRH                   0x114
#define BT1_AXI_WERRH_TYPE              BIT(23)
#define BT1_AXI_WERRH_ADDR_FLD          24
#define BT1_AXI_WERRH_ADDR_MASK         GENMASK(31, BT1_AXI_WERRH_ADDR_FLD)

/*
 * struct bt1_axi - Baikal-T1 AXI-bus private data
 * @dev: Pointer to the device structure.
 * @qos_regs: AXI Interconnect QoS tuning registers.
 * @sys_regs: Baikal-T1 System Controller registers map.
 * @irq: Errors IRQ number.
 * @aclk: AXI reference clock.
 * @arst: AXI Interconnect reset line.
 * @count: Number of errors detected.
 */
struct bt1_axi {
        struct device *dev;

        void __iomem *qos_regs;
        struct regmap *sys_regs;
        int irq;

        struct clk *aclk;

        struct reset_control *arst;

        atomic_t count;
};

static irqreturn_t bt1_axi_isr(int irq, void *data)
{
        struct bt1_axi *axi = data;
        u32 low = 0, high = 0;

        regmap_read(axi->sys_regs, BT1_AXI_WERRL, &low);
        regmap_read(axi->sys_regs, BT1_AXI_WERRH, &high);

        dev_crit_ratelimited(axi->dev,
                "AXI-bus fault %d: %s at 0x%x%08x\n",
                atomic_inc_return(&axi->count),
                high & BT1_AXI_WERRH_TYPE ? "no slave" : "slave protocol error",
                high, low);

        /*
         * Print backtrace on each CPU. This might be pointless if the fault
         * has happened on the same CPU as the IRQ handler is executed or
         * the other core proceeded further execution despite the error.
         * But if it's not, by looking at the trace we would get straight to
         * the cause of the problem.
         */
        trigger_all_cpu_backtrace();

        return IRQ_HANDLED;
}

static void bt1_axi_clear_data(void *data)
{
        struct bt1_axi *axi = data;
        struct platform_device *pdev = to_platform_device(axi->dev);

        platform_set_drvdata(pdev, NULL);
}

static struct bt1_axi *bt1_axi_create_data(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct bt1_axi *axi;
        int ret;

        axi = devm_kzalloc(dev, sizeof(*axi), GFP_KERNEL);
        if (!axi)
                return ERR_PTR(-ENOMEM);

        ret = devm_add_action(dev, bt1_axi_clear_data, axi);
        if (ret) {
                dev_err(dev, "Can't add AXI EHB data clear action\n");
                return ERR_PTR(ret);
        }

        axi->dev = dev;
        atomic_set(&axi->count, 0);
        platform_set_drvdata(pdev, axi);

        return axi;
}

static int bt1_axi_request_regs(struct bt1_axi *axi)
{
        struct platform_device *pdev = to_platform_device(axi->dev);
        struct device *dev = axi->dev;

        axi->sys_regs = syscon_regmap_lookup_by_phandle(dev->of_node, "syscon");
        if (IS_ERR(axi->sys_regs)) {
                dev_err(dev, "Couldn't find syscon registers\n");
                return PTR_ERR(axi->sys_regs);
        }

        axi->qos_regs = devm_platform_ioremap_resource_byname(pdev, "qos");
        if (IS_ERR(axi->qos_regs))
                dev_err(dev, "Couldn't map AXI-bus QoS registers\n");

        return PTR_ERR_OR_ZERO(axi->qos_regs);
}

static int bt1_axi_request_rst(struct bt1_axi *axi)
{
        int ret;

        axi->arst = devm_reset_control_get_optional_exclusive(axi->dev, "arst");
        if (IS_ERR(axi->arst)) {
                dev_warn(axi->dev, "Couldn't get reset control line\n");
                return PTR_ERR(axi->arst);
        }

        ret = reset_control_deassert(axi->arst);
        if (ret)
                dev_err(axi->dev, "Failed to deassert the reset line\n");

        return ret;
}

static void bt1_axi_disable_clk(void *data)
{
        struct bt1_axi *axi = data;

        clk_disable_unprepare(axi->aclk);
}

static int bt1_axi_request_clk(struct bt1_axi *axi)
{
        int ret;

        axi->aclk = devm_clk_get(axi->dev, "aclk");
        if (IS_ERR(axi->aclk)) {
                dev_err(axi->dev, "Couldn't get AXI Interconnect clock\n");
                return PTR_ERR(axi->aclk);
        }

        ret = clk_prepare_enable(axi->aclk);
        if (ret) {
                dev_err(axi->dev, "Couldn't enable the AXI clock\n");
                return ret;
        }

        ret = devm_add_action_or_reset(axi->dev, bt1_axi_disable_clk, axi);
        if (ret)
                dev_err(axi->dev, "Can't add AXI clock disable action\n");

        return ret;
}

static int bt1_axi_request_irq(struct bt1_axi *axi)
{
        struct platform_device *pdev = to_platform_device(axi->dev);
        int ret;

        axi->irq = platform_get_irq(pdev, 0);
        if (axi->irq < 0)
                return axi->irq;

        ret = devm_request_irq(axi->dev, axi->irq, bt1_axi_isr, IRQF_SHARED,
                               "bt1-axi", axi);
        if (ret)
                dev_err(axi->dev, "Couldn't request AXI EHB IRQ\n");

        return ret;
}

static ssize_t count_show(struct device *dev,
                          struct device_attribute *attr, char *buf)
{
        struct bt1_axi *axi = dev_get_drvdata(dev);

        return scnprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&axi->count));
}
static DEVICE_ATTR_RO(count);

static ssize_t inject_error_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        return scnprintf(buf, PAGE_SIZE, "Error injection: bus unaligned\n");
}

static ssize_t inject_error_store(struct device *dev,
                                  struct device_attribute *attr,
                                  const char *data, size_t count)
{
        struct bt1_axi *axi = dev_get_drvdata(dev);

        /*
         * Performing unaligned read from the memory will cause the CM2 bus
         * error while unaligned writing - the AXI bus write error handled
         * by this driver.
         */
        if (sysfs_streq(data, "bus"))
                readb(axi->qos_regs);
        else if (sysfs_streq(data, "unaligned"))
                writeb(0, axi->qos_regs);
        else
                return -EINVAL;

        return count;
}
static DEVICE_ATTR_RW(inject_error);

static struct attribute *bt1_axi_sysfs_attrs[] = {
        &dev_attr_count.attr,
        &dev_attr_inject_error.attr,
        NULL
};
ATTRIBUTE_GROUPS(bt1_axi_sysfs);

static void bt1_axi_remove_sysfs(void *data)
{
        struct bt1_axi *axi = data;

        device_remove_groups(axi->dev, bt1_axi_sysfs_groups);
}

static int bt1_axi_init_sysfs(struct bt1_axi *axi)
{
        int ret;

        ret = device_add_groups(axi->dev, bt1_axi_sysfs_groups);
        if (ret) {
                dev_err(axi->dev, "Failed to add sysfs files group\n");
                return ret;
        }

        ret = devm_add_action_or_reset(axi->dev, bt1_axi_remove_sysfs, axi);
        if (ret)
                dev_err(axi->dev, "Can't add AXI EHB sysfs remove action\n");

        return ret;
}

static int bt1_axi_probe(struct platform_device *pdev)
{
        struct bt1_axi *axi;
        int ret;

        axi = bt1_axi_create_data(pdev);
        if (IS_ERR(axi))
                return PTR_ERR(axi);

        ret = bt1_axi_request_regs(axi);
        if (ret)
                return ret;

        ret = bt1_axi_request_rst(axi);
        if (ret)
                return ret;

        ret = bt1_axi_request_clk(axi);
        if (ret)
                return ret;

        ret = bt1_axi_request_irq(axi);
        if (ret)
                return ret;

        ret = bt1_axi_init_sysfs(axi);
        if (ret)
                return ret;

        return 0;
}

static const struct of_device_id bt1_axi_of_match[] = {
        { .compatible = "baikal,bt1-axi" },
        { }
};
MODULE_DEVICE_TABLE(of, bt1_axi_of_match);

static struct platform_driver bt1_axi_driver = {
        .probe = bt1_axi_probe,
        .driver = {
                .name = "bt1-axi",
                .of_match_table = bt1_axi_of_match
        }
};
module_platform_driver(bt1_axi_driver);

MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");
MODULE_DESCRIPTION("Baikal-T1 AXI-bus driver");
MODULE_LICENSE("GPL v2");