[PATCH v2 2/4] dmaengine: mtk_uart_dma: add Mediatek uart DMA support

[Long Cheng]

In DMA engine framework, add 8250 mtk dma to support it.

Signed-off-by: Long Cheng <long.cheng@xxxxxxxxxxxx>
---
 drivers/dma/mediatek/8250_mtk_dma.c |  894 +++++++++++++++++++++++++++++++++++
 drivers/dma/mediatek/Kconfig        |   11 +
 drivers/dma/mediatek/Makefile       |    1 +
 3 files changed, 906 insertions(+)
 create mode 100644 drivers/dma/mediatek/8250_mtk_dma.c

diff --git a/drivers/dma/mediatek/8250_mtk_dma.c b/drivers/dma/mediatek/8250_mtk_dma.c
new file mode 100644
index 0000000..3454679
--- /dev/null
+++ b/drivers/dma/mediatek/8250_mtk_dma.c
@@ -0,0 +1,894 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mediatek 8250 DMA driver.
+ *
+ * Copyright (c) 2018 MediaTek Inc.
+ * Author: Long Cheng <long.cheng@xxxxxxxxxxxx>
+ */
+
+#include <linux/clk.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/of_dma.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/pm_runtime.h>
+#include <linux/iopoll.h>
+
+#include "../virt-dma.h"
+
+#define MTK_APDMA_DEFAULT_REQUESTS	127
+#define MTK_APDMA_CHANNELS		(CONFIG_SERIAL_8250_NR_UARTS * 2)
+
+#define VFF_EN_B		BIT(0)
+#define VFF_STOP_B		BIT(0)
+#define VFF_FLUSH_B		BIT(0)
+#define VFF_4G_SUPPORT_B	BIT(0)
+#define VFF_RX_INT_EN0_B	BIT(0)	/*rx valid size >=  vff thre*/
+#define VFF_RX_INT_EN1_B	BIT(1)
+#define VFF_TX_INT_EN_B		BIT(0)	/*tx left size >= vff thre*/
+#define VFF_WARM_RST_B		BIT(0)
+#define VFF_RX_INT_FLAG_CLR_B	(BIT(0) | BIT(1))
+#define VFF_TX_INT_FLAG_CLR_B	0
+#define VFF_STOP_CLR_B		0
+#define VFF_FLUSH_CLR_B		0
+#define VFF_INT_EN_CLR_B	0
+#define VFF_4G_SUPPORT_CLR_B	0
+
+/* interrupt trigger level for tx */
+#define VFF_TX_THRE(n)		((n) * 7 / 8)
+/* interrupt trigger level for rx */
+#define VFF_RX_THRE(n)		((n) * 3 / 4)
+
+#define MTK_DMA_RING_SIZE	0xffffU
+/* invert this bit when wrap ring head again*/
+#define MTK_DMA_RING_WRAP	0x10000U
+
+#define VFF_INT_FLAG		0x00
+#define VFF_INT_EN		0x04
+#define VFF_EN			0x08
+#define VFF_RST			0x0c
+#define VFF_STOP		0x10
+#define VFF_FLUSH		0x14
+#define VFF_ADDR		0x1c
+#define VFF_LEN			0x24
+#define VFF_THRE		0x28
+#define VFF_WPT			0x2c
+#define VFF_RPT			0x30
+/*TX: the buffer size HW can read. RX: the buffer size SW can read.*/
+#define VFF_VALID_SIZE		0x3c
+/*TX: the buffer size SW can write. RX: the buffer size HW can write.*/
+#define VFF_LEFT_SIZE		0x40
+#define VFF_DEBUG_STATUS	0x50
+#define VFF_4G_SUPPORT		0x54
+
+struct mtk_dmadev {
+	struct dma_device ddev;
+	void __iomem *mem_base[MTK_APDMA_CHANNELS];
+	spinlock_t lock; /* dma dev lock */
+	struct tasklet_struct task;
+	struct list_head pending;
+	struct clk *clk;
+	unsigned int dma_requests;
+	bool support_33bits;
+	unsigned int dma_irq[MTK_APDMA_CHANNELS];
+	struct mtk_chan *ch[MTK_APDMA_CHANNELS];
+};
+
+struct mtk_chan {
+	struct virt_dma_chan vc;
+	struct list_head node;
+	struct dma_slave_config	cfg;
+	void __iomem *base;
+	struct mtk_dma_desc *desc;
+
+	bool stop;
+	bool requested;
+
+	unsigned int dma_sig;
+	unsigned int dma_ch;
+	unsigned int sgidx;
+	unsigned int remain_size;
+	unsigned int rx_ptr;
+};
+
+struct mtk_dma_sg {
+	dma_addr_t addr;
+	unsigned int en;		/* number of elements (24-bit) */
+	unsigned int fn;		/* number of frames (16-bit) */
+};
+
+struct mtk_dma_desc {
+	struct virt_dma_desc vd;
+	enum dma_transfer_direction dir;
+
+	unsigned int sglen;
+	struct mtk_dma_sg sg[0];
+};
+
+static bool mtk_dma_filter_fn(struct dma_chan *chan, void *param);
+static struct of_dma_filter_info mtk_dma_info = {
+	.filter_fn = mtk_dma_filter_fn,
+};
+
+static inline struct mtk_dmadev *to_mtk_dma_dev(struct dma_device *d)
+{
+	return container_of(d, struct mtk_dmadev, ddev);
+}
+
+static inline struct mtk_chan *to_mtk_dma_chan(struct dma_chan *c)
+{
+	return container_of(c, struct mtk_chan, vc.chan);
+}
+
+static inline struct mtk_dma_desc *to_mtk_dma_desc
+	(struct dma_async_tx_descriptor *t)
+{
+	return container_of(t, struct mtk_dma_desc, vd.tx);
+}
+
+static void mtk_dma_chan_write(struct mtk_chan *c,
+			       unsigned int reg, unsigned int val)
+{
+	writel(val, c->base + reg);
+}
+
+static unsigned int mtk_dma_chan_read(struct mtk_chan *c, unsigned int reg)
+{
+	return readl(c->base + reg);
+}
+
+static void mtk_dma_desc_free(struct virt_dma_desc *vd)
+{
+	struct dma_chan *chan = vd->tx.chan;
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+
+	kfree(c->desc);
+	c->desc = NULL;
+}
+
+static int mtk_dma_clk_enable(struct mtk_dmadev *mtkd)
+{
+	int ret;
+
+	ret = clk_prepare_enable(mtkd->clk);
+	if (ret) {
+		dev_err(mtkd->ddev.dev, "Couldn't enable the clock\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void mtk_dma_clk_disable(struct mtk_dmadev *mtkd)
+{
+	clk_disable_unprepare(mtkd->clk);
+}
+
+static void mtk_dma_remove_virt_list(dma_cookie_t cookie,
+				     struct virt_dma_chan *vc)
+{
+	struct virt_dma_desc *vd;
+
+	if (list_empty(&vc->desc_issued) == 0) {
+		list_for_each_entry(vd, &vc->desc_issued, node) {
+			if (cookie == vd->tx.cookie) {
+				INIT_LIST_HEAD(&vc->desc_issued);
+				break;
+			}
+		}
+	}
+}
+
+static void mtk_dma_tx_flush(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+
+	if (mtk_dma_chan_read(c, VFF_FLUSH) == 0U)
+		mtk_dma_chan_write(c, VFF_FLUSH, VFF_FLUSH_B);
+}
+
+static void mtk_dma_tx_write(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	unsigned int txcount = c->remain_size;
+	unsigned int len, send, left, wpt, wrap;
+
+	len = mtk_dma_chan_read(c, VFF_LEN);
+
+	while ((left = mtk_dma_chan_read(c, VFF_LEFT_SIZE)) > 0U) {
+		if (c->remain_size == 0U)
+			break;
+		send = min(left, c->remain_size);
+		wpt = mtk_dma_chan_read(c, VFF_WPT);
+		wrap = wpt & MTK_DMA_RING_WRAP ? 0U : MTK_DMA_RING_WRAP;
+
+		if ((wpt & (len - 1U)) + send < len)
+			mtk_dma_chan_write(c, VFF_WPT, wpt + send);
+		else
+			mtk_dma_chan_write(c, VFF_WPT,
+					   ((wpt + send) & (len - 1U))
+					   | wrap);
+
+		c->remain_size -= send;
+	}
+
+	if (txcount != c->remain_size) {
+		mtk_dma_chan_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+		mtk_dma_tx_flush(chan);
+	}
+}
+
+static void mtk_dma_start_tx(struct mtk_chan *c)
+{
+	if (mtk_dma_chan_read(c, VFF_LEFT_SIZE) == 0U)
+		mtk_dma_chan_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+	else
+		mtk_dma_tx_write(&c->vc.chan);
+
+	c->stop = false;
+}
+
+static void mtk_dma_get_rx_size(struct mtk_chan *c)
+{
+	unsigned int rx_size = mtk_dma_chan_read(c, VFF_LEN);
+	unsigned int rdptr, wrptr, wrreg, rdreg, count;
+
+	rdreg = mtk_dma_chan_read(c, VFF_RPT);
+	wrreg = mtk_dma_chan_read(c, VFF_WPT);
+	rdptr = rdreg & MTK_DMA_RING_SIZE;
+	wrptr = wrreg & MTK_DMA_RING_SIZE;
+	count = ((rdreg ^ wrreg) & MTK_DMA_RING_WRAP) ?
+			(wrptr + rx_size - rdptr) : (wrptr - rdptr);
+
+	c->remain_size = count;
+	c->rx_ptr = rdptr;
+
+	mtk_dma_chan_write(c, VFF_RPT, wrreg);
+}
+
+static void mtk_dma_start_rx(struct mtk_chan *c)
+{
+	struct dma_chan *chan = &c->vc.chan;
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct mtk_dma_desc *d = c->desc;
+
+	if (mtk_dma_chan_read(c, VFF_VALID_SIZE) == 0U)
+		return;
+
+	if (d && d->vd.tx.cookie != 0) {
+		mtk_dma_get_rx_size(c);
+		mtk_dma_remove_virt_list(d->vd.tx.cookie, &c->vc);
+		vchan_cookie_complete(&d->vd);
+	} else {
+		spin_lock(&mtkd->lock);
+		if (list_empty(&mtkd->pending))
+			list_add_tail(&c->node, &mtkd->pending);
+		spin_unlock(&mtkd->lock);
+		tasklet_schedule(&mtkd->task);
+	}
+}
+
+static void mtk_dma_reset(struct mtk_chan *c)
+{
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(c->vc.chan.device);
+	u32 status;
+	int ret;
+
+	mtk_dma_chan_write(c, VFF_ADDR, 0);
+	mtk_dma_chan_write(c, VFF_THRE, 0);
+	mtk_dma_chan_write(c, VFF_LEN, 0);
+	mtk_dma_chan_write(c, VFF_RST, VFF_WARM_RST_B);
+
+	ret = readx_poll_timeout(readl,
+				 c->base + VFF_EN,
+				 status, status == 0, 10, 100);
+	if (ret) {
+		dev_err(c->vc.chan.device->dev,
+				"dma reset: fail, timeout\n");
+		return;
+	}
+
+	if (c->cfg.direction == DMA_DEV_TO_MEM)
+		mtk_dma_chan_write(c, VFF_RPT, 0);
+	else if (c->cfg.direction == DMA_MEM_TO_DEV)
+		mtk_dma_chan_write(c, VFF_WPT, 0);
+
+	if (mtkd->support_33bits)
+		mtk_dma_chan_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
+}
+
+static void mtk_dma_stop(struct mtk_chan *c)
+{
+	u32 status;
+	int ret;
+
+	mtk_dma_chan_write(c, VFF_FLUSH, VFF_FLUSH_CLR_B);
+	/* Wait for flush */
+	ret = readx_poll_timeout(readl,
+				 c->base + VFF_FLUSH,
+				 status,
+				 (status & VFF_FLUSH_B) != VFF_FLUSH_B,
+				 10, 100);
+	if (ret)
+		dev_err(c->vc.chan.device->dev,
+			"dma stop: polling FLUSH fail, DEBUG=0x%x\n",
+			mtk_dma_chan_read(c, VFF_DEBUG_STATUS));
+
+	/*set stop as 1 -> wait until en is 0 -> set stop as 0*/
+	mtk_dma_chan_write(c, VFF_STOP, VFF_STOP_B);
+	ret = readx_poll_timeout(readl,
+				 c->base + VFF_EN,
+				 status, status == 0, 10, 100);
+	if (ret)
+		dev_err(c->vc.chan.device->dev,
+			"dma stop: polling VFF_EN fail, DEBUG=0x%x\n",
+			mtk_dma_chan_read(c, VFF_DEBUG_STATUS));
+
+	mtk_dma_chan_write(c, VFF_STOP, VFF_STOP_CLR_B);
+	mtk_dma_chan_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
+
+	if (c->cfg.direction == DMA_DEV_TO_MEM)
+		mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_RX_INT_FLAG_CLR_B);
+	else
+		mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_TX_INT_FLAG_CLR_B);
+
+	c->stop = true;
+}
+
+/*
+ * This callback schedules all pending channels. We could be more
+ * clever here by postponing allocation of the real DMA channels to
+ * this point, and freeing them when our virtual channel becomes idle.
+ *
+ * We would then need to deal with 'all channels in-use'
+ */
+static void mtk_dma_sched(unsigned long data)
+{
+	struct mtk_dmadev *mtkd = (struct mtk_dmadev *)data;
+	struct virt_dma_desc *vd;
+	struct mtk_chan *c;
+	dma_cookie_t cookie;
+	unsigned long flags;
+	LIST_HEAD(head);
+
+	spin_lock_irq(&mtkd->lock);
+	list_splice_tail_init(&mtkd->pending, &head);
+	spin_unlock_irq(&mtkd->lock);
+
+	if (!list_empty(&head)) {
+		c = list_first_entry(&head, struct mtk_chan, node);
+		cookie = c->vc.chan.cookie;
+
+		spin_lock_irqsave(&c->vc.lock, flags);
+		if (c->cfg.direction == DMA_DEV_TO_MEM) {
+			list_del_init(&c->node);
+			mtk_dma_start_rx(c);
+		} else if (c->cfg.direction == DMA_MEM_TO_DEV) {
+			vd = vchan_find_desc(&c->vc, cookie);
+			c->desc = to_mtk_dma_desc(&vd->tx);
+			list_del_init(&c->node);
+			mtk_dma_start_tx(c);
+		}
+		spin_unlock_irqrestore(&c->vc.lock, flags);
+	}
+}
+
+static int mtk_dma_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	int ret = -EBUSY;
+
+	pm_runtime_get_sync(mtkd->ddev.dev);
+
+	if (!mtkd->ch[c->dma_ch]) {
+		c->base = mtkd->mem_base[c->dma_ch];
+		mtkd->ch[c->dma_ch] = c;
+		ret = 1;
+	}
+	c->requested = false;
+	mtk_dma_reset(c);
+
+	return ret;
+}
+
+static void mtk_dma_free_chan_resources(struct dma_chan *chan)
+{
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+
+	if (c->requested) {
+		c->requested = false;
+		free_irq(mtkd->dma_irq[c->dma_ch], chan);
+	}
+
+	tasklet_kill(&mtkd->task);
+	tasklet_kill(&c->vc.task);
+
+	c->base = NULL;
+	mtkd->ch[c->dma_ch] = NULL;
+	vchan_free_chan_resources(&c->vc);
+
+	dev_dbg(mtkd->ddev.dev, "freeing channel for %u\n", c->dma_sig);
+	c->dma_sig = 0;
+
+	pm_runtime_put_sync(mtkd->ddev.dev);
+}
+
+static enum dma_status mtk_dma_tx_status(struct dma_chan *chan,
+					 dma_cookie_t cookie,
+					 struct dma_tx_state *txstate)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	enum dma_status ret;
+	unsigned long flags;
+
+	if (!txstate)
+		return DMA_ERROR;
+
+	ret = dma_cookie_status(chan, cookie, txstate);
+	spin_lock_irqsave(&c->vc.lock, flags);
+	if (ret == DMA_IN_PROGRESS) {
+		c->rx_ptr = mtk_dma_chan_read(c, VFF_RPT) & MTK_DMA_RING_SIZE;
+		dma_set_residue(txstate, c->rx_ptr);
+	} else if (ret == DMA_COMPLETE && c->cfg.direction == DMA_DEV_TO_MEM) {
+		dma_set_residue(txstate, c->remain_size);
+	} else {
+		dma_set_residue(txstate, 0);
+	}
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return ret;
+}
+
+static struct dma_async_tx_descriptor *mtk_dma_prep_slave_sg
+	(struct dma_chan *chan, struct scatterlist *sgl,
+	unsigned int sglen,	enum dma_transfer_direction dir,
+	unsigned long tx_flags, void *context)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct scatterlist *sgent;
+	struct mtk_dma_desc *d;
+	struct mtk_dma_sg *sg;
+	unsigned int size, i, j, en;
+
+	en = 1;
+
+	if ((dir != DMA_DEV_TO_MEM) &&
+		(dir != DMA_MEM_TO_DEV)) {
+		dev_err(chan->device->dev, "bad direction\n");
+		return NULL;
+	}
+
+	/* Now allocate and setup the descriptor. */
+	d = kzalloc(sizeof(*d) + sglen * sizeof(d->sg[0]), GFP_ATOMIC);
+	if (!d)
+		return NULL;
+
+	d->dir = dir;
+
+	j = 0;
+	for_each_sg(sgl, sgent, sglen, i) {
+		d->sg[j].addr = sg_dma_address(sgent);
+		d->sg[j].en = en;
+		d->sg[j].fn = sg_dma_len(sgent) / en;
+		j++;
+	}
+
+	d->sglen = j;
+
+	if (dir == DMA_MEM_TO_DEV) {
+		for (size = i = 0; i < d->sglen; i++) {
+			sg = &d->sg[i];
+			size += sg->en * sg->fn;
+		}
+		c->remain_size = size;
+	}
+
+	return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
+}
+
+static void mtk_dma_issue_pending(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct virt_dma_desc *vd;
+	struct mtk_dmadev *mtkd;
+	dma_cookie_t cookie;
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	if (c->cfg.direction == DMA_DEV_TO_MEM) {
+		cookie = c->vc.chan.cookie;
+		mtkd = to_mtk_dma_dev(chan->device);
+		if (vchan_issue_pending(&c->vc) && !c->desc) {
+			vd = vchan_find_desc(&c->vc, cookie);
+			c->desc = to_mtk_dma_desc(&vd->tx);
+		}
+	} else if (c->cfg.direction == DMA_MEM_TO_DEV) {
+		cookie = c->vc.chan.cookie;
+		if (vchan_issue_pending(&c->vc) && !c->desc) {
+			vd = vchan_find_desc(&c->vc, cookie);
+			c->desc = to_mtk_dma_desc(&vd->tx);
+			mtk_dma_start_tx(c);
+		}
+	}
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+}
+
+static irqreturn_t mtk_dma_rx_interrupt(int irq, void *dev_id)
+{
+	struct dma_chan *chan = (struct dma_chan *)dev_id;
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_RX_INT_FLAG_CLR_B);
+
+	mtk_dma_start_rx(c);
+
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t mtk_dma_tx_interrupt(int irq, void *dev_id)
+{
+	struct dma_chan *chan = (struct dma_chan *)dev_id;
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct mtk_dma_desc *d = c->desc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	if (c->remain_size != 0U) {
+		list_add_tail(&c->node, &mtkd->pending);
+		tasklet_schedule(&mtkd->task);
+	} else {
+		mtk_dma_remove_virt_list(d->vd.tx.cookie, &c->vc);
+		vchan_cookie_complete(&d->vd);
+	}
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_TX_INT_FLAG_CLR_B);
+
+	return IRQ_HANDLED;
+}
+
+static int mtk_dma_slave_config(struct dma_chan *chan,
+				struct dma_slave_config *cfg)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(c->vc.chan.device);
+	int ret;
+
+	c->cfg = *cfg;
+
+	if (cfg->direction == DMA_DEV_TO_MEM) {
+		unsigned int rx_len = cfg->src_addr_width * 1024;
+
+		mtk_dma_chan_write(c, VFF_ADDR, cfg->src_addr);
+		mtk_dma_chan_write(c, VFF_LEN, rx_len);
+		mtk_dma_chan_write(c, VFF_THRE, VFF_RX_THRE(rx_len));
+		mtk_dma_chan_write(c,
+				   VFF_INT_EN, VFF_RX_INT_EN0_B
+				   | VFF_RX_INT_EN1_B);
+		mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_RX_INT_FLAG_CLR_B);
+		mtk_dma_chan_write(c, VFF_EN, VFF_EN_B);
+
+		if (!c->requested) {
+			c->requested = true;
+			ret = request_irq(mtkd->dma_irq[c->dma_ch],
+					  mtk_dma_rx_interrupt,
+					  IRQF_TRIGGER_NONE,
+					  KBUILD_MODNAME, chan);
+			if (ret < 0) {
+				dev_err(chan->device->dev, "Can't request rx dma IRQ\n");
+				return -EINVAL;
+			}
+		}
+	} else if (cfg->direction == DMA_MEM_TO_DEV)	{
+		unsigned int tx_len = cfg->dst_addr_width * 1024;
+
+		mtk_dma_chan_write(c, VFF_ADDR, cfg->dst_addr);
+		mtk_dma_chan_write(c, VFF_LEN, tx_len);
+		mtk_dma_chan_write(c, VFF_THRE, VFF_TX_THRE(tx_len));
+		mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_TX_INT_FLAG_CLR_B);
+		mtk_dma_chan_write(c, VFF_EN, VFF_EN_B);
+
+		if (!c->requested) {
+			c->requested = true;
+			ret = request_irq(mtkd->dma_irq[c->dma_ch],
+					  mtk_dma_tx_interrupt,
+					  IRQF_TRIGGER_NONE,
+					  KBUILD_MODNAME, chan);
+			if (ret < 0) {
+				dev_err(chan->device->dev, "Can't request tx dma IRQ\n");
+				return -EINVAL;
+			}
+		}
+	}
+
+	if (mtkd->support_33bits)
+		mtk_dma_chan_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
+
+	if (mtk_dma_chan_read(c, VFF_EN) != VFF_EN_B) {
+		dev_err(chan->device->dev,
+			"config dma dir[%d] fail\n", cfg->direction);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int mtk_dma_terminate_all(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	list_del_init(&c->node);
+	mtk_dma_stop(c);
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return 0;
+}
+
+static int mtk_dma_device_pause(struct dma_chan *chan)
+{
+	/* just for check caps pass */
+	return -EINVAL;
+}
+
+static int mtk_dma_device_resume(struct dma_chan *chan)
+{
+	/* just for check caps pass */
+	return -EINVAL;
+}
+
+static void mtk_dma_free(struct mtk_dmadev *mtkd)
+{
+	tasklet_kill(&mtkd->task);
+	while (list_empty(&mtkd->ddev.channels) == 0) {
+		struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
+			struct mtk_chan, vc.chan.device_node);
+
+		list_del(&c->vc.chan.device_node);
+		tasklet_kill(&c->vc.task);
+		devm_kfree(mtkd->ddev.dev, c);
+	}
+}
+
+static const struct of_device_id mtk_uart_dma_match[] = {
+	{ .compatible = "mediatek,mt6577-uart-dma", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, mtk_uart_dma_match);
+
+static int mtk_apdma_probe(struct platform_device *pdev)
+{
+	struct mtk_dmadev *mtkd;
+	struct resource *res;
+	struct mtk_chan *c;
+	unsigned int i;
+	int rc;
+
+	mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
+	if (!mtkd)
+		return -ENOMEM;
+
+	for (i = 0; i < MTK_APDMA_CHANNELS; i++) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
+		if (!res)
+			return -ENODEV;
+		mtkd->mem_base[i] = devm_ioremap_resource(&pdev->dev, res);
+		if (IS_ERR(mtkd->mem_base[i]))
+			return PTR_ERR(mtkd->mem_base[i]);
+	}
+
+	for (i = 0; i < MTK_APDMA_CHANNELS; i++) {
+		mtkd->dma_irq[i] = platform_get_irq(pdev, i);
+		if ((int)mtkd->dma_irq[i] < 0) {
+			dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
+			return -EINVAL;
+		}
+	}
+
+	mtkd->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(mtkd->clk)) {
+		dev_err(&pdev->dev, "No clock specified\n");
+		return PTR_ERR(mtkd->clk);
+	}
+
+	if (of_property_read_bool(pdev->dev.of_node, "dma-33bits")) {
+		dev_info(&pdev->dev, "Support dma 33bits\n");
+		mtkd->support_33bits = true;
+	}
+
+	if (mtkd->support_33bits)
+		rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(33));
+	else
+		rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	if (rc)
+		return rc;
+
+	dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
+	mtkd->ddev.device_alloc_chan_resources = mtk_dma_alloc_chan_resources;
+	mtkd->ddev.device_free_chan_resources = mtk_dma_free_chan_resources;
+	mtkd->ddev.device_tx_status = mtk_dma_tx_status;
+	mtkd->ddev.device_issue_pending = mtk_dma_issue_pending;
+	mtkd->ddev.device_prep_slave_sg = mtk_dma_prep_slave_sg;
+	mtkd->ddev.device_config = mtk_dma_slave_config;
+	mtkd->ddev.device_pause = mtk_dma_device_pause;
+	mtkd->ddev.device_resume = mtk_dma_device_resume;
+	mtkd->ddev.device_terminate_all = mtk_dma_terminate_all;
+	mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
+	mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
+	mtkd->ddev.dev = &pdev->dev;
+	INIT_LIST_HEAD(&mtkd->ddev.channels);
+	INIT_LIST_HEAD(&mtkd->pending);
+
+	spin_lock_init(&mtkd->lock);
+	tasklet_init(&mtkd->task, mtk_dma_sched, (unsigned long)mtkd);
+
+	mtkd->dma_requests = MTK_APDMA_DEFAULT_REQUESTS;
+	if (of_property_read_u32(pdev->dev.of_node,
+				 "dma-requests", &mtkd->dma_requests)) {
+		dev_info(&pdev->dev,
+			 "Missing dma-requests property, using %u.\n",
+			 MTK_APDMA_DEFAULT_REQUESTS);
+	}
+
+	for (i = 0; i < MTK_APDMA_CHANNELS; i++) {
+		c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
+		if (!c)
+			goto err_no_dma;
+
+		c->vc.desc_free = mtk_dma_desc_free;
+		vchan_init(&c->vc, &mtkd->ddev);
+		INIT_LIST_HEAD(&c->node);
+	}
+
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+
+	rc = dma_async_device_register(&mtkd->ddev);
+	if (rc)
+		goto rpm_disable;
+
+	platform_set_drvdata(pdev, mtkd);
+
+	if (pdev->dev.of_node) {
+		mtk_dma_info.dma_cap = mtkd->ddev.cap_mask;
+
+		/* Device-tree DMA controller registration */
+		rc = of_dma_controller_register(pdev->dev.of_node,
+						of_dma_simple_xlate,
+						&mtk_dma_info);
+		if (rc)
+			goto dma_remove;
+	}
+
+	return rc;
+
+dma_remove:
+	dma_async_device_unregister(&mtkd->ddev);
+rpm_disable:
+	pm_runtime_disable(&pdev->dev);
+err_no_dma:
+	mtk_dma_free(mtkd);
+	return rc;
+}
+
+static int mtk_apdma_remove(struct platform_device *pdev)
+{
+	struct mtk_dmadev *mtkd = platform_get_drvdata(pdev);
+
+	if (pdev->dev.of_node)
+		of_dma_controller_free(pdev->dev.of_node);
+
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
+
+	dma_async_device_unregister(&mtkd->ddev);
+
+	mtk_dma_free(mtkd);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int mtk_dma_suspend(struct device *dev)
+{
+	struct mtk_dmadev *mtkd = dev_get_drvdata(dev);
+
+	if (!pm_runtime_suspended(dev))
+		mtk_dma_clk_disable(mtkd);
+
+	return 0;
+}
+
+static int mtk_dma_resume(struct device *dev)
+{
+	int ret;
+	struct mtk_dmadev *mtkd = dev_get_drvdata(dev);
+
+	if (!pm_runtime_suspended(dev)) {
+		ret = mtk_dma_clk_enable(mtkd);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int mtk_dma_runtime_suspend(struct device *dev)
+{
+	struct mtk_dmadev *mtkd = dev_get_drvdata(dev);
+
+	mtk_dma_clk_disable(mtkd);
+
+	return 0;
+}
+
+static int mtk_dma_runtime_resume(struct device *dev)
+{
+	int ret;
+	struct mtk_dmadev *mtkd = dev_get_drvdata(dev);
+
+	ret = mtk_dma_clk_enable(mtkd);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+#endif /* CONFIG_PM_SLEEP */
+
+static const struct dev_pm_ops mtk_dma_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(mtk_dma_suspend, mtk_dma_resume)
+	SET_RUNTIME_PM_OPS(mtk_dma_runtime_suspend,
+			   mtk_dma_runtime_resume, NULL)
+};
+
+static struct platform_driver mtk_dma_driver = {
+	.probe	= mtk_apdma_probe,
+	.remove	= mtk_apdma_remove,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.pm		= &mtk_dma_pm_ops,
+		.of_match_table = of_match_ptr(mtk_uart_dma_match),
+	},
+};
+
+static bool mtk_dma_filter_fn(struct dma_chan *chan, void *param)
+{
+	if (chan->device->dev->driver == &mtk_dma_driver.driver) {
+		struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+		struct mtk_chan *c = to_mtk_dma_chan(chan);
+		unsigned int req = *(unsigned int *)param;
+
+		if (req <= mtkd->dma_requests) {
+			c->dma_sig = req;
+			c->dma_ch = req;
+			return true;
+		}
+	}
+	return false;
+}
+
+module_platform_driver(mtk_dma_driver);
+
+MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
+MODULE_AUTHOR("Long Cheng <long.cheng@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+
diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
index 27bac0b..bef436e 100644
--- a/drivers/dma/mediatek/Kconfig
+++ b/drivers/dma/mediatek/Kconfig
@@ -1,4 +1,15 @@
 
+config DMA_MTK_UART
+	tristate "MediaTek SoCs APDMA support for UART"
+	depends on OF
+	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
+	help
+	  Support for the UART DMA engine found on MediaTek MTK SoCs.
+	  when 8250 mtk uart is enabled, and if you want to using DMA,
+	  you can enable the config. the DMA engine just only be used
+	  with MediaTek Socs.
+
 config MTK_HSDMA
 	tristate "MediaTek High-Speed DMA controller support"
 	depends on ARCH_MEDIATEK || COMPILE_TEST
diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
index 6e778f8..2f2efd9 100644
--- a/drivers/dma/mediatek/Makefile
+++ b/drivers/dma/mediatek/Makefile
@@ -1 +1,2 @@
+obj-$(CONFIG_DMA_MTK_UART) += 8250_mtk_dma.o
 obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
-- 
1.7.9.5