// SPDX-License-Identifier: GPL-2.0-only
/*
 * Sloppy logic analyzer using GPIOs (to be run on an isolated CPU)
 *
 * Use the 'gpio-sloppy-logic-analyzer' script in the 'tools/gpio' folder for
 * easier usage and further documentation. Note that this is a last resort
 * analyzer which can be affected by latencies and non-deterministic code
 * paths. However, for e.g. remote development, it may be useful to get a first
 * view and aid further debugging.
 *
 * Copyright (C) Wolfram Sang <wsa@sang-engineering.com>
 * Copyright (C) Renesas Electronics Corporation
 */

#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/ktime.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/sizes.h>
#include <linux/timekeeping.h>
#include <linux/types.h>
#include <linux/vmalloc.h>

#define GPIO_LA_NAME "gpio-sloppy-logic-analyzer"
#define GPIO_LA_DEFAULT_BUF_SIZE SZ_256K
/* can be increased but then we need to extend the u8 buffers */
#define GPIO_LA_MAX_PROBES 8
#define GPIO_LA_NUM_TESTS 1024

struct gpio_la_poll_priv {
        struct mutex blob_lock; /* serialize access to the blob (data) */
        u32 buf_idx;
        struct gpio_descs *descs;
        unsigned long delay_ns;
        unsigned long acq_delay;
        struct debugfs_blob_wrapper blob;
        struct dentry *debug_dir;
        struct dentry *blob_dent;
        struct debugfs_blob_wrapper meta;
        struct device *dev;
        unsigned int trig_len;
        u8 *trig_data;
};

static struct dentry *gpio_la_poll_debug_dir;

static __always_inline int gpio_la_get_array(struct gpio_descs *d, unsigned long *sptr)
{
        int ret;

        ret = gpiod_get_array_value(d->ndescs, d->desc, d->info, sptr);
        if (ret == 0 && fatal_signal_pending(current))
                ret = -EINTR;

        return ret;
}

static int fops_capture_set(void *data, u64 val)
{
        struct gpio_la_poll_priv *priv = data;
        u8 *la_buf = priv->blob.data;
        unsigned long state = 0; /* zeroed because GPIO arrays are bitfields */
        unsigned long delay;
        ktime_t start_time;
        unsigned int i;
        int ret;

        if (!val)
                return 0;

        if (!la_buf)
                return -ENOMEM;

        if (!priv->delay_ns)
                return -EINVAL;

        mutex_lock(&priv->blob_lock);
        if (priv->blob_dent) {
                debugfs_remove(priv->blob_dent);
                priv->blob_dent = NULL;
        }

        priv->buf_idx = 0;

        local_irq_disable();
        preempt_disable_notrace();

        /* Measure delay of reading GPIOs */
        start_time = ktime_get();
        for (i = 0; i < GPIO_LA_NUM_TESTS; i++) {
                ret = gpio_la_get_array(priv->descs, &state);
                if (ret)
                        goto out;
        }

        priv->acq_delay = ktime_sub(ktime_get(), start_time) / GPIO_LA_NUM_TESTS;
        if (priv->delay_ns < priv->acq_delay) {
                ret = -ERANGE;
                goto out;
        }

        delay = priv->delay_ns - priv->acq_delay;

        /* Wait for triggers */
        for (i = 0; i < priv->trig_len; i += 2) {
                do {
                        ret = gpio_la_get_array(priv->descs, &state);
                        if (ret)
                                goto out;

                        ndelay(delay);
                } while ((state & priv->trig_data[i]) != priv->trig_data[i + 1]);
        }

        /* With triggers, final state is also the first sample */
        if (priv->trig_len)
                la_buf[priv->buf_idx++] = state;

        /* Sample */
        while (priv->buf_idx < priv->blob.size) {
                ret = gpio_la_get_array(priv->descs, &state);
                if (ret)
                        goto out;

                la_buf[priv->buf_idx++] = state;
                ndelay(delay);
        }
out:
        preempt_enable_notrace();
        local_irq_enable();
        if (ret)
                dev_err(priv->dev, "couldn't read GPIOs: %d\n", ret);

        kfree(priv->trig_data);
        priv->trig_data = NULL;
        priv->trig_len = 0;

        priv->blob_dent = debugfs_create_blob("sample_data", 0400, priv->debug_dir, &priv->blob);
        mutex_unlock(&priv->blob_lock);

        return ret;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_capture, NULL, fops_capture_set, "%llu\n");

static int fops_buf_size_get(void *data, u64 *val)
{
        struct gpio_la_poll_priv *priv = data;

        *val = priv->blob.size;

        return 0;
}

static int fops_buf_size_set(void *data, u64 val)
{
        struct gpio_la_poll_priv *priv = data;
        int ret = 0;
        void *p;

        if (!val)
                return -EINVAL;

        mutex_lock(&priv->blob_lock);

        vfree(priv->blob.data);
        p = vzalloc(val);
        if (!p) {
                val = 0;
                ret = -ENOMEM;
        }

        priv->blob.data = p;
        priv->blob.size = val;

        mutex_unlock(&priv->blob_lock);
        return ret;
}
DEFINE_DEBUGFS_ATTRIBUTE(fops_buf_size, fops_buf_size_get, fops_buf_size_set, "%llu\n");

static int trigger_open(struct inode *inode, struct file *file)
{
        return single_open(file, NULL, inode->i_private);
}

static ssize_t trigger_write(struct file *file, const char __user *ubuf,
                             size_t count, loff_t *offset)
{
        struct seq_file *m = file->private_data;
        struct gpio_la_poll_priv *priv = m->private;
        char *buf;

        /* upper limit is arbitrary but should be less than PAGE_SIZE */
        if (count > 2048 || count & 1)
                return -EINVAL;

        buf = memdup_user(ubuf, count);
        if (IS_ERR(buf))
                return PTR_ERR(buf);

        priv->trig_data = buf;
        priv->trig_len = count;

        return count;
}

static const struct file_operations fops_trigger = {
        .owner = THIS_MODULE,
        .open = trigger_open,
        .write = trigger_write,
        .release = single_release,
};

static int gpio_la_poll_probe(struct platform_device *pdev)
{
        struct gpio_la_poll_priv *priv;
        struct device *dev = &pdev->dev;
        const char *devname = dev_name(dev);
        const char *gpio_names[GPIO_LA_MAX_PROBES];
        char *meta = NULL;
        unsigned int i, meta_len = 0;
        int ret;

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

        ret = devm_mutex_init(dev, &priv->blob_lock);
        if (ret)
                return ret;

        fops_buf_size_set(priv, GPIO_LA_DEFAULT_BUF_SIZE);

        priv->descs = devm_gpiod_get_array(dev, "probe", GPIOD_IN);
        if (IS_ERR(priv->descs))
                return PTR_ERR(priv->descs);

        /* artificial limit to keep 1 byte per sample for now */
        if (priv->descs->ndescs > GPIO_LA_MAX_PROBES)
                return -EFBIG;

        ret = device_property_read_string_array(dev, "probe-names", gpio_names,
                                                priv->descs->ndescs);
        if (ret >= 0 && ret != priv->descs->ndescs)
                ret = -EBADR;
        if (ret < 0)
                return dev_err_probe(dev, ret, "error naming the GPIOs");

        for (i = 0; i < priv->descs->ndescs; i++) {
                unsigned int add_len;
                char *new_meta, *consumer_name;

                if (gpiod_cansleep(priv->descs->desc[i]))
                        return -EREMOTE;

                consumer_name = kasprintf(GFP_KERNEL, "%s: %s", devname, gpio_names[i]);
                if (!consumer_name)
                        return -ENOMEM;
                gpiod_set_consumer_name(priv->descs->desc[i], consumer_name);
                kfree(consumer_name);

                /* '10' is length of 'probe00=\n\0' */
                add_len = strlen(gpio_names[i]) + 10;

                new_meta = devm_krealloc(dev, meta, meta_len + add_len, GFP_KERNEL);
                if (!new_meta)
                        return -ENOMEM;

                meta = new_meta;
                meta_len += snprintf(meta + meta_len, add_len, "probe%02u=%s\n",
                                     i + 1, gpio_names[i]);
        }

        platform_set_drvdata(pdev, priv);
        priv->dev = dev;

        priv->meta.data = meta;
        priv->meta.size = meta_len;
        priv->debug_dir = debugfs_create_dir(devname, gpio_la_poll_debug_dir);
        debugfs_create_blob("meta_data", 0400, priv->debug_dir, &priv->meta);
        debugfs_create_ulong("delay_ns", 0600, priv->debug_dir, &priv->delay_ns);
        debugfs_create_ulong("delay_ns_acquisition", 0400, priv->debug_dir, &priv->acq_delay);
        debugfs_create_file_unsafe("buf_size", 0600, priv->debug_dir, priv, &fops_buf_size);
        debugfs_create_file_unsafe("capture", 0200, priv->debug_dir, priv, &fops_capture);
        debugfs_create_file_unsafe("trigger", 0200, priv->debug_dir, priv, &fops_trigger);

        return 0;
}

static void gpio_la_poll_remove(struct platform_device *pdev)
{
        struct gpio_la_poll_priv *priv = platform_get_drvdata(pdev);

        mutex_lock(&priv->blob_lock);
        debugfs_remove_recursive(priv->debug_dir);
        mutex_unlock(&priv->blob_lock);
}

static const struct of_device_id gpio_la_poll_of_match[] = {
        { .compatible = "gpio-sloppy-logic-analyzer" },
        { }
};
MODULE_DEVICE_TABLE(of, gpio_la_poll_of_match);

static struct platform_driver gpio_la_poll_device_driver = {
        .probe = gpio_la_poll_probe,
        .remove = gpio_la_poll_remove,
        .driver = {
                .name = GPIO_LA_NAME,
                .of_match_table = gpio_la_poll_of_match,
        }
};

static int __init gpio_la_poll_init(void)
{
        gpio_la_poll_debug_dir = debugfs_create_dir(GPIO_LA_NAME, NULL);

        return platform_driver_register(&gpio_la_poll_device_driver);
}
/*
 * Non-strict pin controllers can read GPIOs while being muxed to something else.
 * To support that, we need to claim GPIOs before further pinmuxing happens. So,
 * we probe early using 'late_initcall'
 */
late_initcall(gpio_la_poll_init);

static void __exit gpio_la_poll_exit(void)
{
        platform_driver_unregister(&gpio_la_poll_device_driver);
        debugfs_remove_recursive(gpio_la_poll_debug_dir);
}
module_exit(gpio_la_poll_exit);

MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
MODULE_DESCRIPTION("Sloppy logic analyzer using GPIOs");
MODULE_LICENSE("GPL");