// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2017 Google Inc
 *
 * Provides a simple driver to control the ASPEED LPC snoop interface which
 * allows the BMC to listen on and save the data written by
 * the host to an arbitrary LPC I/O port.
 *
 * Typically used by the BMC to "watch" host boot progress via port
 * 0x80 writes made by the BIOS during the boot process.
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/dev_printk.h>
#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/kfifo.h>
#include <linux/mfd/syscon.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
#include <linux/regmap.h>

#define DEVICE_NAME     "aspeed-lpc-snoop"

#define SNOOP_FIFO_SIZE 2048

#define HICR5   0x80
#define HICR5_EN_SNP0W          BIT(0)
#define HICR5_ENINT_SNP0W       BIT(1)
#define HICR5_EN_SNP1W          BIT(2)
#define HICR5_ENINT_SNP1W       BIT(3)
#define HICR6   0x84
#define HICR6_STR_SNP0W         BIT(0)
#define HICR6_STR_SNP1W         BIT(1)
#define SNPWADR 0x90
#define SNPWADR_CH0_MASK        GENMASK(15, 0)
#define SNPWADR_CH0_SHIFT       0
#define SNPWADR_CH1_MASK        GENMASK(31, 16)
#define SNPWADR_CH1_SHIFT       16
#define SNPWDR  0x94
#define SNPWDR_CH0_MASK         GENMASK(7, 0)
#define SNPWDR_CH0_SHIFT        0
#define SNPWDR_CH1_MASK         GENMASK(15, 8)
#define SNPWDR_CH1_SHIFT        8
#define HICRB   0x100
#define HICRB_ENSNP0D           BIT(14)
#define HICRB_ENSNP1D           BIT(15)

struct aspeed_lpc_snoop_model_data {
        /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
         * can use them.
         */
        unsigned int has_hicrb_ensnp;
};

enum aspeed_lpc_snoop_index {
        ASPEED_LPC_SNOOP_INDEX_0 = 0,
        ASPEED_LPC_SNOOP_INDEX_1 = 1,
        ASPEED_LPC_SNOOP_INDEX_MAX = ASPEED_LPC_SNOOP_INDEX_1,
};

struct aspeed_lpc_snoop_channel_cfg {
        enum aspeed_lpc_snoop_index index;
        u32 hicr5_en;
        u32 snpwadr_mask;
        u32 snpwadr_shift;
        u32 hicrb_en;
};

struct aspeed_lpc_snoop_channel {
        const struct aspeed_lpc_snoop_channel_cfg *cfg;
        bool enabled;
        struct kfifo            fifo;
        wait_queue_head_t       wq;
        struct miscdevice       miscdev;
};

struct aspeed_lpc_snoop {
        struct regmap           *regmap;
        int                     irq;
        struct clk              *clk;
        struct aspeed_lpc_snoop_channel chan[ASPEED_LPC_SNOOP_INDEX_MAX + 1];
};

static const struct aspeed_lpc_snoop_channel_cfg channel_cfgs[ASPEED_LPC_SNOOP_INDEX_MAX + 1] = {
        {
                .index = ASPEED_LPC_SNOOP_INDEX_0,
                .hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
                .snpwadr_mask = SNPWADR_CH0_MASK,
                .snpwadr_shift = SNPWADR_CH0_SHIFT,
                .hicrb_en = HICRB_ENSNP0D,
        },
        {
                .index = ASPEED_LPC_SNOOP_INDEX_1,
                .hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
                .snpwadr_mask = SNPWADR_CH1_MASK,
                .snpwadr_shift = SNPWADR_CH1_SHIFT,
                .hicrb_en = HICRB_ENSNP1D,
        },
};

static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
{
        return container_of(file->private_data,
                            struct aspeed_lpc_snoop_channel,
                            miscdev);
}

static ssize_t snoop_file_read(struct file *file, char __user *buffer,
                                size_t count, loff_t *ppos)
{
        struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
        unsigned int copied;
        int ret = 0;

        if (kfifo_is_empty(&chan->fifo)) {
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;
                ret = wait_event_interruptible(chan->wq,
                                !kfifo_is_empty(&chan->fifo));
                if (ret == -ERESTARTSYS)
                        return -EINTR;
        }
        ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
        if (ret)
                return ret;

        return copied;
}

static __poll_t snoop_file_poll(struct file *file,
                                    struct poll_table_struct *pt)
{
        struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);

        poll_wait(file, &chan->wq, pt);
        return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
}

static const struct file_operations snoop_fops = {
        .owner  = THIS_MODULE,
        .read   = snoop_file_read,
        .poll   = snoop_file_poll,
        .llseek = noop_llseek,
};

/* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
{
        if (!kfifo_initialized(&chan->fifo))
                return;
        if (kfifo_is_full(&chan->fifo))
                kfifo_skip(&chan->fifo);
        kfifo_put(&chan->fifo, val);
        wake_up_interruptible(&chan->wq);
}

static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
{
        struct aspeed_lpc_snoop *lpc_snoop = arg;
        u32 reg, data;

        if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
                return IRQ_NONE;

        /* Check if one of the snoop channels is interrupting */
        reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
        if (!reg)
                return IRQ_NONE;

        /* Ack pending IRQs */
        regmap_write(lpc_snoop->regmap, HICR6, reg);

        /* Read and save most recent snoop'ed data byte to FIFO */
        regmap_read(lpc_snoop->regmap, SNPWDR, &data);

        if (reg & HICR6_STR_SNP0W) {
                u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;

                put_fifo_with_discard(&lpc_snoop->chan[0], val);
        }
        if (reg & HICR6_STR_SNP1W) {
                u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;

                put_fifo_with_discard(&lpc_snoop->chan[1], val);
        }

        return IRQ_HANDLED;
}

static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
                                       struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        int rc;

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

        rc = devm_request_irq(dev, lpc_snoop->irq,
                              aspeed_lpc_snoop_irq, IRQF_SHARED,
                              DEVICE_NAME, lpc_snoop);
        if (rc < 0) {
                dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
                lpc_snoop->irq = 0;
                return rc;
        }

        return 0;
}

__attribute__((nonnull))
static int aspeed_lpc_enable_snoop(struct device *dev,
                                    struct aspeed_lpc_snoop *lpc_snoop,
                                    struct aspeed_lpc_snoop_channel *channel,
                                    const struct aspeed_lpc_snoop_channel_cfg *cfg,
                                    u16 lpc_port)
{
        const struct aspeed_lpc_snoop_model_data *model_data;
        int rc = 0;

        if (WARN_ON(channel->enabled))
                return -EBUSY;

        init_waitqueue_head(&channel->wq);

        channel->cfg = cfg;
        channel->miscdev.minor = MISC_DYNAMIC_MINOR;
        channel->miscdev.fops = &snoop_fops;
        channel->miscdev.parent = dev;

        channel->miscdev.name =
                devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, cfg->index);
        if (!channel->miscdev.name)
                return -ENOMEM;

        rc = kfifo_alloc(&channel->fifo, SNOOP_FIFO_SIZE, GFP_KERNEL);
        if (rc)
                return rc;

        rc = misc_register(&channel->miscdev);
        if (rc)
                goto err_free_fifo;

        /* Enable LPC snoop channel at requested port */
        regmap_set_bits(lpc_snoop->regmap, HICR5, cfg->hicr5_en);
        regmap_update_bits(lpc_snoop->regmap, SNPWADR, cfg->snpwadr_mask,
                           lpc_port << cfg->snpwadr_shift);

        model_data = of_device_get_match_data(dev);
        if (model_data && model_data->has_hicrb_ensnp)
                regmap_set_bits(lpc_snoop->regmap, HICRB, cfg->hicrb_en);

        channel->enabled = true;

        return 0;

err_free_fifo:
        kfifo_free(&channel->fifo);
        return rc;
}

__attribute__((nonnull))
static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
                                     struct aspeed_lpc_snoop_channel *channel)
{
        if (!channel->enabled)
                return;

        /* Disable interrupts along with the device */
        regmap_clear_bits(lpc_snoop->regmap, HICR5, channel->cfg->hicr5_en);

        channel->enabled = false;
        /* Consider improving safety wrt concurrent reader(s) */
        misc_deregister(&channel->miscdev);
        kfifo_free(&channel->fifo);
}

static void aspeed_lpc_snoop_remove(struct platform_device *pdev)
{
        struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);

        /* Disable both snoop channels */
        aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[0]);
        aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[1]);
}

static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
{
        struct aspeed_lpc_snoop *lpc_snoop;
        struct device_node *np;
        struct device *dev;
        int idx;
        int rc;

        dev = &pdev->dev;

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

        np = pdev->dev.parent->of_node;
        if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
            !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
            !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
                dev_err(dev, "unsupported LPC device binding\n");
                return -ENODEV;
        }

        lpc_snoop->regmap = syscon_node_to_regmap(np);
        if (IS_ERR(lpc_snoop->regmap))
                return dev_err_probe(dev, PTR_ERR(lpc_snoop->regmap), "Couldn't get regmap\n");

        dev_set_drvdata(&pdev->dev, lpc_snoop);

        lpc_snoop->clk = devm_clk_get_enabled(dev, NULL);
        if (IS_ERR(lpc_snoop->clk))
                return dev_err_probe(dev, PTR_ERR(lpc_snoop->clk), "couldn't get clock");

        rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
        if (rc)
                return rc;

        static_assert(ARRAY_SIZE(channel_cfgs) == ARRAY_SIZE(lpc_snoop->chan),
                "Broken implementation assumption regarding cfg count");
        for (idx = ASPEED_LPC_SNOOP_INDEX_0; idx <= ASPEED_LPC_SNOOP_INDEX_MAX; idx++) {
                u32 port;

                rc = of_property_read_u32_index(dev->of_node, "snoop-ports", idx, &port);
                if (rc)
                        break;

                rc = aspeed_lpc_enable_snoop(dev, lpc_snoop, &lpc_snoop->chan[idx],
                                             &channel_cfgs[idx], port);
                if (rc)
                        goto cleanup_channels;
        }

        return idx == ASPEED_LPC_SNOOP_INDEX_0 ? -ENODEV : 0;

cleanup_channels:
        aspeed_lpc_snoop_remove(pdev);

        return rc;
}

static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
        .has_hicrb_ensnp = 0,
};

static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
        .has_hicrb_ensnp = 1,
};

static const struct of_device_id aspeed_lpc_snoop_match[] = {
        { .compatible = "aspeed,ast2400-lpc-snoop",
          .data = &ast2400_model_data },
        { .compatible = "aspeed,ast2500-lpc-snoop",
          .data = &ast2500_model_data },
        { .compatible = "aspeed,ast2600-lpc-snoop",
          .data = &ast2500_model_data },
        { },
};

static struct platform_driver aspeed_lpc_snoop_driver = {
        .driver = {
                .name           = DEVICE_NAME,
                .of_match_table = aspeed_lpc_snoop_match,
        },
        .probe = aspeed_lpc_snoop_probe,
        .remove = aspeed_lpc_snoop_remove,
};

module_platform_driver(aspeed_lpc_snoop_driver);

MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");