// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Driver for the Loongson-2 APB DMA Controller
 *
 * Copyright (C) 2017-2023 Loongson Corporation
 */

#include <linux/clk.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#include "../dmaengine.h"
#include "../virt-dma.h"

/* Global Configuration Register */
#define LDMA_ORDER_ERG		0x0

/* Bitfield definitions */

/* Bitfields in Global Configuration Register */
#define LDMA_64BIT_EN		BIT(0) /* 1: 64 bit support */
#define LDMA_UNCOHERENT_EN	BIT(1) /* 0: cache, 1: uncache */
#define LDMA_ASK_VALID		BIT(2)
#define LDMA_START		BIT(3) /* DMA start operation */
#define LDMA_STOP		BIT(4) /* DMA stop operation */
#define LDMA_CONFIG_MASK	GENMASK_ULL(4, 0) /* DMA controller config bits mask */

/* Bitfields in ndesc_addr field of HW descriptor */
#define LDMA_DESC_EN		BIT(0) /*1: The next descriptor is valid */
#define LDMA_DESC_ADDR_LOW	GENMASK(31, 1)

/* Bitfields in cmd field of HW descriptor */
#define LDMA_INT		BIT(1) /* Enable DMA interrupts */
#define LDMA_DATA_DIRECTION	BIT(12) /* 1: write to device, 0: read from device */

#define LDMA_SLAVE_BUSWIDTHS	(BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) | \
				 BIT(DMA_SLAVE_BUSWIDTH_8_BYTES))

#define LDMA_MAX_TRANS_LEN	U32_MAX

/*--  descriptors  -----------------------------------------------------*/

/*
 * struct ls2x_dma_hw_desc - DMA HW descriptor
 * @ndesc_addr: the next descriptor low address.
 * @mem_addr: memory low address.
 * @apb_addr: device buffer address.
 * @len: length of a piece of carried content, in words.
 * @step_len: length between two moved memory data blocks.
 * @step_times: number of blocks to be carried in a single DMA operation.
 * @cmd: descriptor command or state.
 * @stats: DMA status.
 * @high_ndesc_addr: the next descriptor high address.
 * @high_mem_addr: memory high address.
 * @reserved: reserved
 */
struct ls2x_dma_hw_desc {
	u32 ndesc_addr;
	u32 mem_addr;
	u32 apb_addr;
	u32 len;
	u32 step_len;
	u32 step_times;
	u32 cmd;
	u32 stats;
	u32 high_ndesc_addr;
	u32 high_mem_addr;
	u32 reserved[2];
} __packed;

/*
 * struct ls2x_dma_sg - ls2x dma scatter gather entry
 * @hw: the pointer to DMA HW descriptor.
 * @llp: physical address of the DMA HW descriptor.
 * @phys: destination or source address(mem).
 * @len: number of Bytes to read.
 */
struct ls2x_dma_sg {
	struct ls2x_dma_hw_desc	*hw;
	dma_addr_t		llp;
	dma_addr_t		phys;
	u32			len;
};

/*
 * struct ls2x_dma_desc - software descriptor
 * @vdesc: pointer to the virtual dma descriptor.
 * @cyclic: flag to dma cyclic
 * @burst_size: burst size of transaction, in words.
 * @desc_num: number of sg entries.
 * @direction: transfer direction, to or from device.
 * @status: dma controller status.
 * @sg: array of sgs.
 */
struct ls2x_dma_desc {
	struct virt_dma_desc		vdesc;
	bool				cyclic;
	size_t				burst_size;
	u32				desc_num;
	enum dma_transfer_direction	direction;
	enum dma_status			status;
	struct ls2x_dma_sg		sg[] __counted_by(desc_num);
};

/*--  Channels  --------------------------------------------------------*/

/*
 * struct ls2x_dma_chan - internal representation of an LS2X APB DMA channel
 * @vchan: virtual dma channel entry.
 * @desc: pointer to the ls2x sw dma descriptor.
 * @pool: hw desc table
 * @irq: irq line
 * @sconfig: configuration for slave transfers, passed via .device_config
 */
struct ls2x_dma_chan {
	struct virt_dma_chan	vchan;
	struct ls2x_dma_desc	*desc;
	void			*pool;
	int			irq;
	struct dma_slave_config	sconfig;
};

/*--  Controller  ------------------------------------------------------*/

/*
 * struct ls2x_dma_priv - LS2X APB DMAC specific information
 * @ddev: dmaengine dma_device object members
 * @dma_clk: DMAC clock source
 * @regs: memory mapped register base
 * @lchan: channel to store ls2x_dma_chan structures
 */
struct ls2x_dma_priv {
	struct dma_device	ddev;
	struct clk		*dma_clk;
	void __iomem		*regs;
	struct ls2x_dma_chan	lchan;
};

/*--  Helper functions  ------------------------------------------------*/

static inline struct ls2x_dma_desc *to_ldma_desc(struct virt_dma_desc *vdesc)
{
	return container_of(vdesc, struct ls2x_dma_desc, vdesc);
}

static inline struct ls2x_dma_chan *to_ldma_chan(struct dma_chan *chan)
{
	return container_of(chan, struct ls2x_dma_chan, vchan.chan);
}

static inline struct ls2x_dma_priv *to_ldma_priv(struct dma_device *ddev)
{
	return container_of(ddev, struct ls2x_dma_priv, ddev);
}

static struct device *chan2dev(struct dma_chan *chan)
{
	return &chan->dev->device;
}

static void ls2x_dma_desc_free(struct virt_dma_desc *vdesc)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(vdesc->tx.chan);
	struct ls2x_dma_desc *desc = to_ldma_desc(vdesc);
	int i;

	for (i = 0; i < desc->desc_num; i++) {
		if (desc->sg[i].hw)
			dma_pool_free(lchan->pool, desc->sg[i].hw,
				      desc->sg[i].llp);
	}

	kfree(desc);
}

static void ls2x_dma_write_cmd(struct ls2x_dma_chan *lchan, bool cmd)
{
	struct ls2x_dma_priv *priv = to_ldma_priv(lchan->vchan.chan.device);
	u64 val;

	val = lo_hi_readq(priv->regs + LDMA_ORDER_ERG) & ~LDMA_CONFIG_MASK;
	val |= LDMA_64BIT_EN | cmd;
	lo_hi_writeq(val, priv->regs + LDMA_ORDER_ERG);
}

static void ls2x_dma_start_transfer(struct ls2x_dma_chan *lchan)
{
	struct ls2x_dma_priv *priv = to_ldma_priv(lchan->vchan.chan.device);
	struct ls2x_dma_sg *ldma_sg;
	struct virt_dma_desc *vdesc;
	u64 val;

	/* Get the next descriptor */
	vdesc = vchan_next_desc(&lchan->vchan);
	if (!vdesc) {
		lchan->desc = NULL;
		return;
	}

	list_del(&vdesc->node);
	lchan->desc = to_ldma_desc(vdesc);
	ldma_sg = &lchan->desc->sg[0];

	/* Start DMA */
	lo_hi_writeq(0, priv->regs + LDMA_ORDER_ERG);
	val = (ldma_sg->llp & ~LDMA_CONFIG_MASK) | LDMA_64BIT_EN | LDMA_START;
	lo_hi_writeq(val, priv->regs + LDMA_ORDER_ERG);
}

static size_t ls2x_dmac_detect_burst(struct ls2x_dma_chan *lchan)
{
	u32 maxburst, buswidth;

	/* Reject definitely invalid configurations */
	if ((lchan->sconfig.src_addr_width & LDMA_SLAVE_BUSWIDTHS) &&
	    (lchan->sconfig.dst_addr_width & LDMA_SLAVE_BUSWIDTHS))
		return 0;

	if (lchan->sconfig.direction == DMA_MEM_TO_DEV) {
		maxburst = lchan->sconfig.dst_maxburst;
		buswidth = lchan->sconfig.dst_addr_width;
	} else {
		maxburst = lchan->sconfig.src_maxburst;
		buswidth = lchan->sconfig.src_addr_width;
	}

	/* If maxburst is zero, fallback to LDMA_MAX_TRANS_LEN */
	return maxburst ? (maxburst * buswidth) >> 2 : LDMA_MAX_TRANS_LEN;
}

static void ls2x_dma_fill_desc(struct ls2x_dma_chan *lchan, u32 sg_index,
			       struct ls2x_dma_desc *desc)
{
	struct ls2x_dma_sg *ldma_sg = &desc->sg[sg_index];
	u32 num_segments, segment_size;

	if (desc->direction == DMA_MEM_TO_DEV) {
		ldma_sg->hw->cmd = LDMA_INT | LDMA_DATA_DIRECTION;
		ldma_sg->hw->apb_addr = lchan->sconfig.dst_addr;
	} else {
		ldma_sg->hw->cmd = LDMA_INT;
		ldma_sg->hw->apb_addr = lchan->sconfig.src_addr;
	}

	ldma_sg->hw->mem_addr = lower_32_bits(ldma_sg->phys);
	ldma_sg->hw->high_mem_addr = upper_32_bits(ldma_sg->phys);

	/* Split into multiple equally sized segments if necessary */
	num_segments = DIV_ROUND_UP((ldma_sg->len + 3) >> 2, desc->burst_size);
	segment_size = DIV_ROUND_UP((ldma_sg->len + 3) >> 2, num_segments);

	/* Word count register takes input in words */
	ldma_sg->hw->len = segment_size;
	ldma_sg->hw->step_times = num_segments;
	ldma_sg->hw->step_len = 0;

	/* lets make a link list */
	if (sg_index) {
		desc->sg[sg_index - 1].hw->ndesc_addr = ldma_sg->llp | LDMA_DESC_EN;
		desc->sg[sg_index - 1].hw->high_ndesc_addr = upper_32_bits(ldma_sg->llp);
	}
}

/*--  DMA Engine API  --------------------------------------------------*/

/*
 * ls2x_dma_alloc_chan_resources - allocate resources for DMA channel
 * @chan: allocate descriptor resources for this channel
 *
 * return - the number of allocated descriptors
 */
static int ls2x_dma_alloc_chan_resources(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	/* Create a pool of consistent memory blocks for hardware descriptors */
	lchan->pool = dma_pool_create(dev_name(chan2dev(chan)),
				      chan->device->dev, PAGE_SIZE,
				      __alignof__(struct ls2x_dma_hw_desc), 0);
	if (!lchan->pool) {
		dev_err(chan2dev(chan), "No memory for descriptors\n");
		return -ENOMEM;
	}

	return 1;
}

/*
 * ls2x_dma_free_chan_resources - free all channel resources
 * @chan: DMA channel
 */
static void ls2x_dma_free_chan_resources(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	vchan_free_chan_resources(to_virt_chan(chan));
	dma_pool_destroy(lchan->pool);
	lchan->pool = NULL;
}

/*
 * ls2x_dma_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
 * @chan: DMA channel
 * @sgl: scatterlist to transfer to/from
 * @sg_len: number of entries in @scatterlist
 * @direction: DMA direction
 * @flags: tx descriptor status flags
 * @context: transaction context (ignored)
 *
 * Return: Async transaction descriptor on success and NULL on failure
 */
static struct dma_async_tx_descriptor *
ls2x_dma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
		       u32 sg_len, enum dma_transfer_direction direction,
		       unsigned long flags, void *context)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);
	struct ls2x_dma_desc *desc;
	struct scatterlist *sg;
	size_t burst_size;
	int i;

	if (unlikely(!sg_len || !is_slave_direction(direction)))
		return NULL;

	burst_size = ls2x_dmac_detect_burst(lchan);
	if (!burst_size)
		return NULL;

	desc = kzalloc_flex(*desc, sg, sg_len, GFP_NOWAIT);
	if (!desc)
		return NULL;

	desc->desc_num = sg_len;
	desc->direction = direction;
	desc->burst_size = burst_size;

	for_each_sg(sgl, sg, sg_len, i) {
		struct ls2x_dma_sg *ldma_sg = &desc->sg[i];

		/* Allocate DMA capable memory for hardware descriptor */
		ldma_sg->hw = dma_pool_alloc(lchan->pool, GFP_NOWAIT, &ldma_sg->llp);
		if (!ldma_sg->hw) {
			desc->desc_num = i;
			ls2x_dma_desc_free(&desc->vdesc);
			return NULL;
		}

		ldma_sg->phys = sg_dma_address(sg);
		ldma_sg->len = sg_dma_len(sg);

		ls2x_dma_fill_desc(lchan, i, desc);
	}

	/* Setting the last descriptor enable bit */
	desc->sg[sg_len - 1].hw->ndesc_addr &= ~LDMA_DESC_EN;
	desc->status = DMA_IN_PROGRESS;

	return vchan_tx_prep(&lchan->vchan, &desc->vdesc, flags);
}

/*
 * ls2x_dma_prep_dma_cyclic - prepare the cyclic DMA transfer
 * @chan: the DMA channel to prepare
 * @buf_addr: physical DMA address where the buffer starts
 * @buf_len: total number of bytes for the entire buffer
 * @period_len: number of bytes for each period
 * @direction: transfer direction, to or from device
 * @flags: tx descriptor status flags
 *
 * Return: Async transaction descriptor on success and NULL on failure
 */
static struct dma_async_tx_descriptor *
ls2x_dma_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
			 size_t period_len, enum dma_transfer_direction direction,
			 unsigned long flags)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);
	struct ls2x_dma_desc *desc;
	size_t burst_size;
	u32 num_periods;
	int i;

	if (unlikely(!buf_len || !period_len))
		return NULL;

	if (unlikely(!is_slave_direction(direction)))
		return NULL;

	burst_size = ls2x_dmac_detect_burst(lchan);
	if (!burst_size)
		return NULL;

	num_periods = buf_len / period_len;
	desc = kzalloc_flex(*desc, sg, num_periods, GFP_NOWAIT);
	if (!desc)
		return NULL;

	desc->desc_num = num_periods;
	desc->direction = direction;
	desc->burst_size = burst_size;

	/* Build cyclic linked list */
	for (i = 0; i < num_periods; i++) {
		struct ls2x_dma_sg *ldma_sg = &desc->sg[i];

		/* Allocate DMA capable memory for hardware descriptor */
		ldma_sg->hw = dma_pool_alloc(lchan->pool, GFP_NOWAIT, &ldma_sg->llp);
		if (!ldma_sg->hw) {
			desc->desc_num = i;
			ls2x_dma_desc_free(&desc->vdesc);
			return NULL;
		}

		ldma_sg->phys = buf_addr + period_len * i;
		ldma_sg->len = period_len;

		ls2x_dma_fill_desc(lchan, i, desc);
	}

	/* Lets make a cyclic list */
	desc->sg[num_periods - 1].hw->ndesc_addr = desc->sg[0].llp | LDMA_DESC_EN;
	desc->sg[num_periods - 1].hw->high_ndesc_addr = upper_32_bits(desc->sg[0].llp);
	desc->cyclic = true;
	desc->status = DMA_IN_PROGRESS;

	return vchan_tx_prep(&lchan->vchan, &desc->vdesc, flags);
}

/*
 * ls2x_slave_config - set slave configuration for channel
 * @chan: dma channel
 * @cfg: slave configuration
 *
 * Sets slave configuration for channel
 */
static int ls2x_dma_slave_config(struct dma_chan *chan,
				 struct dma_slave_config *config)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	memcpy(&lchan->sconfig, config, sizeof(*config));
	return 0;
}

/*
 * ls2x_dma_issue_pending - push pending transactions to the hardware
 * @chan: channel
 *
 * When this function is called, all pending transactions are pushed to the
 * hardware and executed.
 */
static void ls2x_dma_issue_pending(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	guard(spinlock_irqsave)(&lchan->vchan.lock);

	if (vchan_issue_pending(&lchan->vchan) && !lchan->desc)
		ls2x_dma_start_transfer(lchan);
}

/*
 * ls2x_dma_terminate_all - terminate all transactions
 * @chan: channel
 *
 * Stops all DMA transactions.
 */
static int ls2x_dma_terminate_all(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);
	LIST_HEAD(head);

	scoped_guard(spinlock_irqsave, &lchan->vchan.lock) {
		/* Setting stop cmd */
		ls2x_dma_write_cmd(lchan, LDMA_STOP);
		if (lchan->desc) {
			vchan_terminate_vdesc(&lchan->desc->vdesc);
			lchan->desc = NULL;
		}

		vchan_get_all_descriptors(&lchan->vchan, &head);
	}

	vchan_dma_desc_free_list(&lchan->vchan, &head);
	return 0;
}

/*
 * ls2x_dma_synchronize - Synchronizes the termination of transfers to the
 * current context.
 * @chan: channel
 */
static void ls2x_dma_synchronize(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	vchan_synchronize(&lchan->vchan);
}

static int ls2x_dma_pause(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	guard(spinlock_irqsave)(&lchan->vchan.lock);

	if (lchan->desc && lchan->desc->status == DMA_IN_PROGRESS) {
		ls2x_dma_write_cmd(lchan, LDMA_STOP);
		lchan->desc->status = DMA_PAUSED;
	}

	return 0;
}

static int ls2x_dma_resume(struct dma_chan *chan)
{
	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);

	guard(spinlock_irqsave)(&lchan->vchan.lock);

	if (lchan->desc && lchan->desc->status == DMA_PAUSED) {
		lchan->desc->status = DMA_IN_PROGRESS;
		ls2x_dma_write_cmd(lchan, LDMA_START);
	}

	return 0;
}

/*
 * ls2x_dma_isr - LS2X DMA Interrupt handler
 * @irq: IRQ number
 * @dev_id: Pointer to ls2x_dma_chan
 *
 * Return: IRQ_HANDLED/IRQ_NONE
 */
static irqreturn_t ls2x_dma_isr(int irq, void *dev_id)
{
	struct ls2x_dma_chan *lchan = dev_id;
	struct ls2x_dma_desc *desc;

	scoped_guard(spinlock, &lchan->vchan.lock) {
		desc = lchan->desc;
		if (desc) {
			if (desc->cyclic) {
				vchan_cyclic_callback(&desc->vdesc);
			} else {
				desc->status = DMA_COMPLETE;
				vchan_cookie_complete(&desc->vdesc);
				ls2x_dma_start_transfer(lchan);
			}

			/* ls2x_dma_start_transfer() updates lchan->desc */
			if (!lchan->desc)
				ls2x_dma_write_cmd(lchan, LDMA_STOP);
		}
	}

	return IRQ_HANDLED;
}

static int ls2x_dma_chan_init(struct platform_device *pdev,
			      struct ls2x_dma_priv *priv)
{
	struct ls2x_dma_chan *lchan = &priv->lchan;
	struct device *dev = &pdev->dev;
	int ret;

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

	ret = devm_request_irq(dev, lchan->irq, ls2x_dma_isr, IRQF_TRIGGER_RISING,
			       dev_name(&pdev->dev), lchan);
	if (ret)
		return ret;

	/* Initialize channels related values */
	INIT_LIST_HEAD(&priv->ddev.channels);
	lchan->vchan.desc_free = ls2x_dma_desc_free;
	vchan_init(&lchan->vchan, &priv->ddev);

	return 0;
}

/*
 * ls2x_dma_probe - Driver probe function
 * @pdev: Pointer to the platform_device structure
 *
 * Return: '0' on success and failure value on error
 */
static int ls2x_dma_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct ls2x_dma_priv *priv;
	struct dma_device *ddev;
	int ret;

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

	priv->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->regs))
		return dev_err_probe(dev, PTR_ERR(priv->regs),
				     "devm_platform_ioremap_resource failed.\n");

	priv->dma_clk = devm_clk_get_enabled(dev, NULL);
	if (IS_ERR(priv->dma_clk))
		return dev_err_probe(dev, PTR_ERR(priv->dma_clk), "Couldn't start the clock.\n");

	ret = ls2x_dma_chan_init(pdev, priv);
	if (ret)
		return ret;

	ddev = &priv->ddev;
	ddev->dev = dev;
	dma_cap_zero(ddev->cap_mask);
	dma_cap_set(DMA_SLAVE, ddev->cap_mask);
	dma_cap_set(DMA_CYCLIC, ddev->cap_mask);

	ddev->device_alloc_chan_resources = ls2x_dma_alloc_chan_resources;
	ddev->device_free_chan_resources = ls2x_dma_free_chan_resources;
	ddev->device_tx_status = dma_cookie_status;
	ddev->device_issue_pending = ls2x_dma_issue_pending;
	ddev->device_prep_slave_sg = ls2x_dma_prep_slave_sg;
	ddev->device_prep_dma_cyclic = ls2x_dma_prep_dma_cyclic;
	ddev->device_config = ls2x_dma_slave_config;
	ddev->device_terminate_all = ls2x_dma_terminate_all;
	ddev->device_synchronize = ls2x_dma_synchronize;
	ddev->device_pause = ls2x_dma_pause;
	ddev->device_resume = ls2x_dma_resume;

	ddev->src_addr_widths = LDMA_SLAVE_BUSWIDTHS;
	ddev->dst_addr_widths = LDMA_SLAVE_BUSWIDTHS;
	ddev->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);

	ret = dmaenginem_async_device_register(&priv->ddev);
	if (ret < 0)
		return dev_err_probe(dev, ret, "Failed to register DMA engine device.\n");

	ret = of_dma_controller_register(dev->of_node, of_dma_xlate_by_chan_id, priv);
	if (ret < 0)
		return dev_err_probe(dev, ret, "Failed to register dma controller.\n");

	platform_set_drvdata(pdev, priv);

	dev_info(dev, "Loongson LS2X APB DMA driver registered successfully.\n");
	return 0;
}

/*
 * ls2x_dma_remove - Driver remove function
 * @pdev: Pointer to the platform_device structure
 */
static void ls2x_dma_remove(struct platform_device *pdev)
{
	of_dma_controller_free(pdev->dev.of_node);
}

static const struct of_device_id ls2x_dma_of_match_table[] = {
	{ .compatible = "loongson,ls2k1000-apbdma" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ls2x_dma_of_match_table);

static struct platform_driver ls2x_dmac_driver = {
	.probe		= ls2x_dma_probe,
	.remove		= ls2x_dma_remove,
	.driver = {
		.name	= "ls2x-apbdma",
		.of_match_table	= ls2x_dma_of_match_table,
	},
};
module_platform_driver(ls2x_dmac_driver);

MODULE_DESCRIPTION("Loongson-2 APB DMA Controller driver");
MODULE_AUTHOR("Loongson Technology Corporation Limited");
MODULE_LICENSE("GPL");