dmaengine: ls2x-apb: New driver for the Loongson LS2X APB DMA controller

The Loongson LS2X APB DMA controller is available on Loongson-2K chips.

It is a single-channel, configurable DMA controller IP core based on the
AXI bus, whose main function is to integrate DMA functionality on a chip
dedicated to carrying data between memory and peripherals in APB bus
(e.g. nand).

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Yingkun Meng <mengyingkun@loongson.cn>
Link: https://lore.kernel.org/r/8df2a0199434fba3535831082966c2442ecf1cae.1702365725.git.zhoubinbin@loongson.cn
Signed-off-by: Vinod Koul <vkoul@kernel.org>

3 files changed, 720 insertions, 0 deletions

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 70ba506dabab..e928f2ca0f1e 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -378,6 +378,20 @@ config LPC18XX_DMAMUX
 	  Enable support for DMA on NXP LPC18xx/43xx platforms
 	  with PL080 and multiplexed DMA request lines.
 
+config LS2X_APB_DMA
+	tristate "Loongson LS2X APB DMA support"
+	depends on LOONGARCH || COMPILE_TEST
+	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
+	help
+	  Support for the Loongson LS2X APB DMA controller driver. The
+	  DMA controller is having single DMA channel which can be
+	  configured for different peripherals like audio, nand, sdio
+	  etc which is in APB bus.
+
+	  This DMA controller transfers data from memory to peripheral fifo.
+	  It does not support memory to memory data transfer.
+
 config MCF_EDMA
 	tristate "Freescale eDMA engine support, ColdFire mcf5441x SoCs"
 	depends on M5441x || COMPILE_TEST
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 83553a97a010..dfd40d14e408 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_INTEL_IOATDMA) += ioat/
 obj-y += idxd/
 obj-$(CONFIG_K3_DMA) += k3dma.o
 obj-$(CONFIG_LPC18XX_DMAMUX) += lpc18xx-dmamux.o
+obj-$(CONFIG_LS2X_APB_DMA) += ls2x-apb-dma.o
 obj-$(CONFIG_MILBEAUT_HDMAC) += milbeaut-hdmac.o
 obj-$(CONFIG_MILBEAUT_XDMAC) += milbeaut-xdmac.o
 obj-$(CONFIG_MMP_PDMA) += mmp_pdma.o
diff --git a/drivers/dma/ls2x-apb-dma.c b/drivers/dma/ls2x-apb-dma.c
new file mode 100644
index 000000000000..a49913f3ed3f
--- /dev/null
+++ b/drivers/dma/ls2x-apb-dma.c
@@ -0,0 +1,705 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for the Loongson LS2X 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(4, 0) /* DMA controller config bits mask */
+
+/* Bitfields in ndesc_addr field of HW decriptor */
+#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 decriptor */
+#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(struct_size(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(struct_size(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);
+	unsigned long flags;
+
+	spin_lock_irqsave(&lchan->vchan.lock, flags);
+	if (vchan_issue_pending(&lchan->vchan) && !lchan->desc)
+		ls2x_dma_start_transfer(lchan);
+	spin_unlock_irqrestore(&lchan->vchan.lock, flags);
+}
+
+/*
+ * 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);
+	unsigned long flags;
+	LIST_HEAD(head);
+
+	spin_lock_irqsave(&lchan->vchan.lock, flags);
+	/* 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);
+	spin_unlock_irqrestore(&lchan->vchan.lock, flags);
+
+	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);
+	unsigned long flags;
+
+	spin_lock_irqsave(&lchan->vchan.lock, flags);
+	if (lchan->desc && lchan->desc->status == DMA_IN_PROGRESS) {
+		ls2x_dma_write_cmd(lchan, LDMA_STOP);
+		lchan->desc->status = DMA_PAUSED;
+	}
+	spin_unlock_irqrestore(&lchan->vchan.lock, flags);
+
+	return 0;
+}
+
+static int ls2x_dma_resume(struct dma_chan *chan)
+{
+	struct ls2x_dma_chan *lchan = to_ldma_chan(chan);
+	unsigned long flags;
+
+	spin_lock_irqsave(&lchan->vchan.lock, flags);
+	if (lchan->desc && lchan->desc->status == DMA_PAUSED) {
+		lchan->desc->status = DMA_IN_PROGRESS;
+		ls2x_dma_write_cmd(lchan, LDMA_START);
+	}
+	spin_unlock_irqrestore(&lchan->vchan.lock, flags);
+
+	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;
+
+	spin_lock(&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);
+	}
+	spin_unlock(&lchan->vchan.lock);
+
+	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(&pdev->dev, NULL);
+	if (IS_ERR(priv->dma_clk))
+		return dev_err_probe(dev, PTR_ERR(priv->dma_clk), "devm_clk_get failed.\n");
+
+	ret = clk_prepare_enable(priv->dma_clk);
+	if (ret)
+		return dev_err_probe(dev, ret, "clk_prepare_enable failed.\n");
+
+	ret = ls2x_dma_chan_init(pdev, priv);
+	if (ret)
+		goto disable_clk;
+
+	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 = dma_async_device_register(&priv->ddev);
+	if (ret < 0)
+		goto disable_clk;
+
+	ret = of_dma_controller_register(dev->of_node, of_dma_xlate_by_chan_id, priv);
+	if (ret < 0)
+		goto unregister_dmac;
+
+	platform_set_drvdata(pdev, priv);
+
+	dev_info(dev, "Loongson LS2X APB DMA driver registered successfully.\n");
+	return 0;
+
+unregister_dmac:
+	dma_async_device_unregister(&priv->ddev);
+disable_clk:
+	clk_disable_unprepare(priv->dma_clk);
+
+	return ret;
+}
+
+/*
+ * ls2x_dma_remove - Driver remove function
+ * @pdev: Pointer to the platform_device structure
+ */
+static void ls2x_dma_remove(struct platform_device *pdev)
+{
+	struct ls2x_dma_priv *priv = platform_get_drvdata(pdev);
+
+	of_dma_controller_free(pdev->dev.of_node);
+	dma_async_device_unregister(&priv->ddev);
+	clk_disable_unprepare(priv->dma_clk);
+}
+
+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_new	= ls2x_dma_remove,
+	.driver = {
+		.name	= "ls2x-apbdma",
+		.of_match_table	= ls2x_dma_of_match_table,
+	},
+};
+module_platform_driver(ls2x_dmac_driver);
+
+MODULE_DESCRIPTION("Loongson LS2X APB DMA Controller driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited");
+MODULE_LICENSE("GPL");