// SPDX-License-Identifier: GPL-2.0
/*
 * Phytium I2C adapter driver.
 *
 * Copyright (c) 2021-2023 Phytium Technology Co., Ltd.
 */
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/reset.h>

#include "i2c-phytium-core.h"

static int i2c_phytium_init_master(struct phytium_i2c_dev *dev)
{
	/* Disable the adapter */
	__i2c_phytium_disable(dev);

	/* Write standard speed timing parameters */
	phytium_writel(dev, dev->ss_hcnt, IC_SS_SCL_HCNT);
	phytium_writel(dev, dev->ss_lcnt, IC_SS_SCL_LCNT);

	/* Write fast mode/fast mode plus timing parameters */
	phytium_writel(dev, dev->fs_hcnt, IC_FS_SCL_HCNT);
	phytium_writel(dev, dev->fs_lcnt, IC_FS_SCL_LCNT);

	/* Write high speed timing parameters if supported */
	if (dev->hs_hcnt && dev->hs_hcnt) {
		phytium_writel(dev, dev->hs_hcnt, IC_HS_SCL_HCNT);
		phytium_writel(dev, dev->hs_lcnt, IC_HS_SCL_LCNT);
	}

	/* Write SDA hold time if supported */
	if (dev->sda_hold_time)
		phytium_writel(dev, dev->sda_hold_time, IC_SDA_HOLD);

	/* Configure Tx/Rx FIFO threshold levels */
	phytium_writel(dev, dev->tx_fifo_depth >> 1, IC_TX_TL);
	phytium_writel(dev, 0, IC_RX_TL);

	/* Configure the I2C master */
	phytium_writel(dev, dev->master_cfg, IC_CON);

	return 0;
}

static void i2c_phytium_xfer_init(struct phytium_i2c_dev *dev)
{
	struct i2c_msg *msgs = dev->msgs;
	u32 ic_con, ic_tar = 0;

	/* Disable the adapter */
	__i2c_phytium_disable(dev);

	/* If the slave address is 10-bit address, enable 10BITADDR */
	ic_con = phytium_readl(dev, IC_CON);
	if (msgs[dev->msg_write_idx].flags & I2C_M_TEN) {
		ic_con |= IC_CON_10BITADDR_MASTER;
		ic_tar = IC_TAR_10BITADDR_MASTER;
	} else {
		ic_con &= ~IC_CON_10BITADDR_MASTER;
	}

	phytium_writel(dev, ic_con, IC_CON);

	/*
	 * Set the slave (target) address and enable 10-bit addressing mode
	 * if applicable.
	 */
	phytium_writel(dev, msgs[dev->msg_write_idx].addr | ic_tar, IC_TAR);

	/* Enforce disabled interrupts */
	i2c_phytium_disable_int(dev);

	/* Enable the adapter */
	__i2c_phytium_enable(dev);

	/* Dummy read */
	phytium_readl(dev, IC_ENABLE_STATUS);

	/* Clear and enable interrupts */
	phytium_readl(dev, IC_CLR_INTR);
	phytium_writel(dev, IC_INTR_SMBUS_MASK, IC_INTR_MASK);
}

static void i2c_phytium_xfer_msg(struct phytium_i2c_dev *dev)
{
	struct i2c_msg *msgs = dev->msgs;
	u32 intr_mask;
	int tx_limit, rx_limit;
	u32 addr = msgs[dev->msg_write_idx].addr;
	u32 buf_len = dev->tx_buf_len;
	u8 *buf = dev->tx_buf;
	bool need_restart = false;

	intr_mask = IC_INTR_MASTER_MASK;

	for (; dev->msg_write_idx < dev->msgs_num; dev->msg_write_idx++) {
		u32 flags = msgs[dev->msg_write_idx].flags;

		if (msgs[dev->msg_write_idx].addr != addr) {
			dev_err(dev->dev,
				"%s: invalid target address\n", __func__);
			dev->msg_err = -EINVAL;
			break;
		}

		if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) {
			/* new i2c_msg */
			buf = msgs[dev->msg_write_idx].buf;
			buf_len = msgs[dev->msg_write_idx].len;

			if ((dev->master_cfg & IC_CON_RESTART_EN) &&
			    (dev->msg_write_idx > 0))
				need_restart = true;
		}

		tx_limit = dev->tx_fifo_depth - phytium_readl(dev, IC_TXFLR);
		rx_limit = dev->tx_fifo_depth - phytium_readl(dev, IC_RXFLR);

		while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
			u32 cmd = 0;

			if (dev->msg_write_idx == dev->msgs_num - 1 &&
			    buf_len == 1 && !(flags & I2C_M_RECV_LEN))
				cmd |= BIT(9);

			if (need_restart) {
				cmd |= BIT(10);
				need_restart = false;
			}

			if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
				/* avoid rx buffer overrun */
				if (dev->rx_outstanding >= dev->rx_fifo_depth)
					break;

				phytium_writel(dev, cmd | 0x100, IC_DATA_CMD);
				rx_limit--;
				dev->rx_outstanding++;
			} else {
				phytium_writel(dev, cmd | *buf++, IC_DATA_CMD);
			}
			tx_limit--;
			buf_len--;
		}

		dev->tx_buf = buf;
		dev->tx_buf_len = buf_len;

		/*
		 * Because we don't know the buffer length in the
		 * I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop
		 * the transaction here.
		 */
		if (buf_len > 0 || flags & I2C_M_RECV_LEN) {
			/* more bytes to be written */
			dev->status |= STATUS_WRITE_IN_PROGRESS;
			break;
		}

		dev->status &= ~STATUS_WRITE_IN_PROGRESS;
	}

	if (dev->msg_write_idx == dev->msgs_num)
		intr_mask &= ~IC_INTR_TX_EMPTY;

	if (dev->msg_err)
		intr_mask = 0;

	phytium_writel(dev, intr_mask,  IC_INTR_MASK);
}

static u8 i2c_phytium_recv_len(struct phytium_i2c_dev *dev, u8 len)
{
	struct i2c_msg *msgs = dev->msgs;
	u32 flags = msgs[dev->msg_read_idx].flags;

	/*
	 * Adjust the buffer length and mask the flag
	 * after receiving the first byte.
	 */
	len += (flags & I2C_CLIENT_PEC) ? 2 : 1;
	dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding);
	msgs[dev->msg_read_idx].len = len;
	msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;

	return len;
}

static void i2c_phytium_read(struct phytium_i2c_dev *dev)
{
	struct i2c_msg *msgs = dev->msgs;
	int rx_valid;

	for (; dev->msg_read_idx < dev->msgs_num; dev->msg_read_idx++) {
		u32 len;
		u8 *buf;

		if (!(msgs[dev->msg_read_idx].flags & I2C_M_RD))
			continue;

		if (!(dev->status & STATUS_READ_IN_PROGRESS)) {
			len = msgs[dev->msg_read_idx].len;
			buf = msgs[dev->msg_read_idx].buf;
		} else {
			len = dev->rx_buf_len;
			buf = dev->rx_buf;
		}

		rx_valid = phytium_readl(dev, IC_RXFLR);

		for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
			u32 flags = msgs[dev->msg_read_idx].flags;

			*buf = phytium_readl(dev, IC_DATA_CMD);
			/* Ensure length byte is a valid value */
			if (flags & I2C_M_RECV_LEN &&
				*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0) {
				len = i2c_phytium_recv_len(dev, *buf);
			}
			buf++;
			dev->rx_outstanding--;
		}

		if (len > 0) {
			dev->status |= STATUS_READ_IN_PROGRESS;
			dev->rx_buf_len = len;
			dev->rx_buf = buf;
			break;
		}

		dev->status &= ~STATUS_READ_IN_PROGRESS;
	}
}

static int i2c_phytium_xfer(struct i2c_adapter *adapter, struct i2c_msg msgs[], int num)
{
	struct phytium_i2c_dev *dev = i2c_get_adapdata(adapter);
	int ret;

	dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);

	pm_runtime_get_sync(dev->dev);

	reinit_completion(&dev->cmd_complete);
	dev->msgs = msgs;
	dev->msgs_num = num;
	dev->cmd_err = 0;
	dev->msg_write_idx = 0;
	dev->msg_read_idx = 0;
	dev->msg_err = 0;
	dev->status = STATUS_IDLE;
	dev->abort_source = 0;
	dev->rx_outstanding = 0;

	ret = i2c_phytium_wait_bus_not_busy(dev);
	if (ret < 0)
		goto done;

	/* Start the transfers */
	i2c_phytium_xfer_init(dev);

	/* Wait for tx to complete */
	if (!wait_for_completion_timeout(&dev->cmd_complete, adapter->timeout)) {
		dev_err(dev->dev, "controller timed out\n");
		i2c_recover_bus(&dev->adapter);
		i2c_phytium_init_master(dev);
		ret = -ETIMEDOUT;
		goto done;
	}

	__i2c_phytium_disable_nowait(dev);

	if (dev->msg_err) {
		ret = dev->msg_err;
		goto done;
	}

	if (likely(!dev->cmd_err && !dev->status)) {
		ret = num;
		goto done;
	}

	/* We have got an error */
	if (dev->cmd_err == IC_ERR_TX_ABRT) {
		ret = i2c_phytium_handle_tx_abort(dev);
		goto done;
	}

	if (dev->status)
		dev_err(dev->dev, "transfer terminated early.\n");

	ret = -EIO;

done:
	pm_runtime_mark_last_busy(dev->dev);
	pm_runtime_put_autosuspend(dev->dev);

	return ret;
}

static const struct i2c_algorithm i2c_phytium_algo = {
	.master_xfer = i2c_phytium_xfer,
	.functionality = i2c_phytium_func,
};

static const struct i2c_adapter_quirks i2c_phytium_quirks = {
	.flags = I2C_AQ_NO_ZERO_LEN,
};

static u32 i2c_phytium_read_clear_intrbits(struct phytium_i2c_dev *dev)
{
	u32 stat;

	stat = phytium_readl(dev, IC_INTR_STAT);

	if (stat & IC_INTR_RX_UNDER)
		phytium_readl(dev, IC_CLR_RX_UNDER);
	if (stat & IC_INTR_RX_OVER)
		phytium_readl(dev, IC_CLR_RX_OVER);
	if (stat & IC_INTR_TX_OVER)
		phytium_readl(dev, IC_CLR_TX_OVER);
	if (stat & IC_INTR_RD_REQ)
		phytium_readl(dev, IC_CLR_RD_REQ);
	if (stat & IC_INTR_TX_ABRT) {
		dev->abort_source = phytium_readl(dev, IC_TX_ABRT_SOURCE);
		phytium_readl(dev, IC_CLR_TX_ABRT);
	}
	if (stat & IC_INTR_RX_DONE)
		phytium_readl(dev, IC_CLR_RX_DONE);
	if (stat & IC_INTR_ACTIVITY)
		phytium_readl(dev, IC_CLR_ACTIVITY);
	if (stat & IC_INTR_STOP_DET)
		phytium_readl(dev, IC_CLR_STOP_DET);
	if (stat & IC_INTR_START_DET)
		phytium_readl(dev, IC_CLR_START_DET);
	if (stat & IC_INTR_GEN_CALL)
		phytium_readl(dev, IC_CLR_GEN_CALL);
	if (stat & IC_INTR_SMBCLK_EXT_LOW_TIMEOUT)
		phytium_readl(dev, IC_CLR_SMBCLK_EXT_LOW_TIMEOUT);
	if (stat & IC_INTR_SMBCLK_TMO_LOW_TIMEOUT)
		phytium_readl(dev, IC_CLR_SMBCLK_TMO_LOW_TIMEOUT);
	if (stat & IC_INTR_SMBSDA_LOW_TIMEOUT)
		phytium_readl(dev, IC_CLR_SMBDAT_LOW_TIMEOUT);
	if (stat & IC_INTR_SMBALERT_IN_N)
		phytium_readl(dev, IC_CLR_SMBALERT_IN_N);

	return stat;
}

static int i2c_phytium_irq_handler_master(struct phytium_i2c_dev *dev)
{
	u32 stat;

	stat = i2c_phytium_read_clear_intrbits(dev);

	/* SMBus interrupt */
	if (stat & (IC_INTR_SMBCLK_EXT_LOW_TIMEOUT | IC_INTR_SMBCLK_TMO_LOW_TIMEOUT)) {
		phytium_writel(dev, phytium_readl(dev, IC_ENABLE) & (~BIT(6)),
			       IC_ENABLE);
		phytium_writel(dev, phytium_readl(dev, IC_ENABLE) | BIT(4),
			       IC_ENABLE);
		goto abort;
	}

	if (stat & IC_INTR_SMBSDA_LOW_TIMEOUT) {
		phytium_writel(dev, phytium_readl(dev, IC_ENABLE) | BIT(6),
			       IC_ENABLE);
		goto abort;
	}

	if (stat & IC_INTR_SMBALERT_IN_N && dev->ara)
		i2c_handle_smbus_alert(dev->ara);

	if (stat & IC_INTR_TX_ABRT) {
		dev->cmd_err |= IC_ERR_TX_ABRT;
		dev->status = STATUS_IDLE;

		/* Anytime TX_ABRT is set, the contents of the tx/rx
		 * buffers are flushed. Make sure to skip them.
		 */
		phytium_writel(dev, 0, IC_INTR_MASK);
		goto abort;
	}

	if (stat & IC_INTR_RX_FULL)
		i2c_phytium_read(dev);

	if (stat & IC_INTR_TX_EMPTY)
		i2c_phytium_xfer_msg(dev);

abort:
	if ((stat & (IC_INTR_TX_ABRT | IC_INTR_STOP_DET)) ||
	    dev->msg_err)
		complete(&dev->cmd_complete);
	else if (unlikely(dev->flags & ACCESS_INTR_MASK)) {
		/* Workaround to trigger pending interrupt */
		stat = phytium_readl(dev, IC_INTR_MASK);
		i2c_phytium_disable_int(dev);
		phytium_writel(dev, stat, IC_INTR_MASK);
	}

	return 0;
}

static int i2c_phytium_set_timings_master(struct phytium_i2c_dev *dev)
{
	const char *mode_str, *fp_str = "";
	u32 sda_falling_time, scl_falling_time;
	struct i2c_timings *t = &dev->timings;
	u32 ic_clk;
	int ret;

	/* Set standard and fast speed dividers for high/low periods */
	sda_falling_time = t->sda_fall_ns ?: 300; /* ns */
	scl_falling_time = t->scl_fall_ns ?: 300; /* ns */

	/* Calculate SCL timing parameters for standard mode if not set */
	if (!dev->ss_hcnt || !dev->ss_lcnt) {
		ic_clk = i2c_phytium_clk_rate(dev);
		dev->ss_hcnt =
			i2c_phytium_scl_hcnt(ic_clk,
					4000, /* tHD;STA = tHIGH = 4.0 us */
					sda_falling_time,
					0,	/* 0: DW default, 1: Ideal */
					0);	/* No offset */
		dev->ss_lcnt =
			i2c_phytium_scl_lcnt(ic_clk,
					4700,	/* tLOW = 4.7 us */
					scl_falling_time,
					0);	/* No offset */
	}
	dev_dbg(dev->dev, "Standard Mode HCNT:LCNT = %d:%d\n",
		dev->ss_hcnt, dev->ss_lcnt);
	/*
	 * Set SCL timing parameters for fast mode or fast mode plus. Only
	 * difference is the timing parameter values since the registers are
	 * the same.
	 */
	if (t->bus_freq_hz == 1000000) {
		/*
		 * Check are fast mode plus parameters available and use
		 * fast mode if not.
		 */
		if (dev->fp_hcnt && dev->fp_lcnt) {
			dev->fs_hcnt = dev->fp_hcnt;
			dev->fs_lcnt = dev->fp_lcnt;
			fp_str = " Plus";
		}
	}
	/*
	 * Calculate SCL timing parameters for fast mode if not set. They are
	 * needed also in high speed mode.
	 */
	if (!dev->fs_hcnt || !dev->fs_lcnt) {
		ic_clk = i2c_phytium_clk_rate(dev);
		dev->fs_hcnt =
			i2c_phytium_scl_hcnt(ic_clk,
					600,	/* tHD;STA = tHIGH = 0.6 us */
					sda_falling_time,
					0,	/* 0: DW default, 1: Ideal */
					0);	/* No offset */
		dev->fs_lcnt =
			i2c_phytium_scl_lcnt(ic_clk,
					1300,	/* tLOW = 1.3 us */
					scl_falling_time,
					0);	/* No offset */
	}
	dev_dbg(dev->dev, "Fast Mode%s HCNT:LCNT = %d:%d\n",
		fp_str, dev->fs_hcnt, dev->fs_lcnt);

	if (dev->hs_hcnt && dev->hs_lcnt)
		dev_dbg(dev->dev, "High Speed Mode HCNT:LCNT = %d:%d\n",
			dev->hs_hcnt, dev->hs_lcnt);

	ret = i2c_phytium_set_sda_hold(dev);
	if (ret)
		goto out;

	switch (dev->master_cfg & IC_CON_SPEED_MASK) {
	case IC_CON_SPEED_STD:
		mode_str = "Standard Mode";
		break;
	case IC_CON_SPEED_HIGH:
		mode_str = "High Speed Mode";
		break;
	default:
		mode_str = "Fast Mode";
	}
	dev_dbg(dev->dev, "Bus speed: %s%s\n", mode_str, fp_str);

out:
	return ret;
}

static irqreturn_t i2c_phytium_isr(int this_irq, void *dev_id)
{
	struct phytium_i2c_dev *dev = dev_id;
	u32 stat, enabled;

	enabled = phytium_readl(dev, IC_ENABLE);
	stat = phytium_readl(dev, IC_RAW_INTR_STAT);
	if (!enabled || !(stat & ~IC_INTR_ACTIVITY))
		return IRQ_NONE;

	i2c_phytium_irq_handler_master(dev);

	return IRQ_HANDLED;
}

int i2c_phytium_probe(struct phytium_i2c_dev *dev)
{
	struct i2c_adapter *adapter = &dev->adapter;
	unsigned long irq_flags;
	int ret;

	init_completion(&dev->cmd_complete);

	dev->init = i2c_phytium_init_master;
	dev->disable = i2c_phytium_disable;
	dev->disable_int = i2c_phytium_disable_int;

	ret = i2c_phytium_set_timings_master(dev);
	if (ret)
		return ret;

	ret = dev->init(dev);
	if (ret)
		return ret;

	/* XXX: should be initialized in firmware, remove it in future */
#define DEFAULT_TIMEOUT	(DEFAULT_CLOCK_FREQUENCY / 1000 * 35)
	phytium_writel(dev, DEFAULT_TIMEOUT, IC_SMBCLK_LOW_MEXT);
	phytium_writel(dev, DEFAULT_TIMEOUT, IC_SMBCLK_LOW_TIMEOUT);
	phytium_writel(dev, DEFAULT_TIMEOUT, IC_SMBDAT_STUCK_TIMEOUT);

	snprintf(adapter->name, sizeof(adapter->name), "Phytium I2C adapter");
	adapter->retries = 3;
	adapter->algo = &i2c_phytium_algo;
	adapter->quirks = &i2c_phytium_quirks;
	adapter->dev.parent = dev->dev;
	i2c_set_adapdata(adapter, dev);

	irq_flags = IRQF_SHARED | IRQF_COND_SUSPEND;

	i2c_phytium_disable_int(dev);
	ret = devm_request_irq(dev->dev, dev->irq, i2c_phytium_isr, irq_flags,
			       dev_name(dev->dev), dev);
	if (ret) {
		dev_err(dev->dev, "failed to request irq %i: %d\n", dev->irq, ret);
		return ret;
	}

	/*
	 * Increment PM usage count during adapter registration in order to
	 * avoid possible spurious runtime suspend when adapter device is
	 * registered to the device core and immediate resume in case bus has
	 * registered I2C slaves that do I2C transfers in their probe.
	 */
	pm_runtime_get_noresume(dev->dev);
	ret = i2c_add_numbered_adapter(adapter);
	if (ret)
		dev_err(dev->dev, "fail to add adapter: %d\n", ret);
	pm_runtime_put_noidle(dev->dev);

	return ret;
}
EXPORT_SYMBOL_GPL(i2c_phytium_probe);

MODULE_DESCRIPTION("Phytium I2C bus master adapter");
MODULE_LICENSE("GPL");