[PATCH 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/Kconfig        |    9 +
 drivers/dma/Makefile       |    1 +
 drivers/dma/mtk_uart_dma.c |  955 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 965 insertions(+)
 create mode 100644 drivers/dma/mtk_uart_dma.c

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 263495d..d76dc96 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -128,6 +128,15 @@ config DMA_JZ4780
 	  If you have a board based on such a SoC and wish to use DMA for
 	  devices which can use the DMA controller, say Y or M here.
 
+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.
+	  This DMA engine just only if used when 8250 mtk uart is enabled.
+
 config DMA_OMAP
 	tristate "OMAP DMA support"
 	depends on ARCH_OMAP || COMPILE_TEST
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index a4fa336..5f0404a 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_COH901318) += coh901318.o coh901318_lli.o
 obj-$(CONFIG_DMA_BCM2835) += bcm2835-dma.o
 obj-$(CONFIG_DMA_JZ4740) += dma-jz4740.o
 obj-$(CONFIG_DMA_JZ4780) += dma-jz4780.o
+obj-$(CONFIG_DMA_MTK_UART) += mtk_uart_dma.o
 obj-$(CONFIG_DMA_OMAP) += omap-dma.o
 obj-$(CONFIG_DMA_SA11X0) += sa11x0-dma.o
 obj-$(CONFIG_DMA_SUN4I) += sun4i-dma.o
diff --git a/drivers/dma/mtk_uart_dma.c b/drivers/dma/mtk_uart_dma.c
new file mode 100644
index 0000000..b884079
--- /dev/null
+++ b/drivers/dma/mtk_uart_dma.c
@@ -0,0 +1,955 @@
+/*
+ * MTK DMAengine support
+ *
+ * Copyright (c) 2016 MediaTek Inc.
+ * Author: Long Cheng (Long) <long.cheng@xxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.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 "virt-dma.h"
+
+#define MTK_SDMA_REQUESTS	127
+#define MTK_SDMA_CHANNELS	8
+#define MTK_POLLING_CNT	10000
+
+#define DRV_NAME	"mtk-uart-dma"
+
+/*---------------------------------------------------------------------------*/
+#define VFF_INT_FLAG_CLR_B	0
+/*VFF_INT_EN*/
+#define VFF_RX_INT_EN0_B	BIT(0)
+#define VFF_RX_INT_EN1_B	BIT(1)
+#define VFF_TX_INT_EN_B		BIT(0)
+#define VFF_INT_EN_CLR_B	0
+/*VFF_RST*/
+#define VFF_WARM_RST_B		BIT(0)
+/*VFF_EN*/
+#define VFF_EN_B		BIT(0)
+/*VFF_STOP*/
+#define VFF_STOP_B		BIT(0)
+#define VFF_STOP_CLR_B		0
+/*VFF_FLUSH*/
+#define VFF_FLUSH_B		BIT(0)
+#define VFF_FLUSH_CLR_B		0
+
+#define VFF_TX_THRE(n)		((n)*7/8)
+#define VFF_RX_THRE(n)		((n)*3/4)
+
+/*---------------------------------------------------------------------------*/
+
+struct mtk_dmadev {
+	struct dma_device ddev;
+	spinlock_t lock;
+	struct tasklet_struct task;
+	struct list_head pending;
+	void __iomem *base;
+	int irq;
+	struct clk *clk;
+	unsigned int dma_requests;
+	uint32_t irq_enable_mask;
+	struct mtk_chan *lch_map[MTK_SDMA_CHANNELS];
+};
+
+struct mtk_chan {
+	struct virt_dma_chan vc;
+	struct list_head node;
+	void __iomem *channel_base;
+	uint32_t ccr;
+
+	struct dma_slave_config	cfg;
+	unsigned int dma_sig;
+	bool paused;
+	bool requested;
+
+	int dma_ch;
+	struct mtk_desc *desc;
+	unsigned int sgidx;
+
+	size_t trig;
+	size_t remain_size;
+	size_t rx_ptr;
+
+	/*sync*/
+	struct completion done;	/* dma transfer done */
+	spinlock_t lock;
+	atomic_t loopcnt;
+	atomic_t entry;		/* entry count */
+};
+
+struct mtk_sg {
+	dma_addr_t addr;
+	uint32_t en;		/* number of elements (24-bit) */
+	uint32_t fn;		/* number of frames (16-bit) */
+};
+
+struct mtk_desc {
+	struct virt_dma_desc vd;
+	enum dma_transfer_direction dir;
+	dma_addr_t dev_addr;
+
+	unsigned int sglen;
+	struct mtk_sg sg[0];
+};
+
+enum {
+	VFF_INT_FLAG		= 0x00,
+	VFF_INT_EN		= 0x04,
+	VFF_EN			= 0x08,
+	VFF_RST			= 0x0c,
+	VFF_STOP		= 0x10,
+	VFF_FLUSH		= 0x14,
+	VFF_ADDR		= 0x1c,
+	VFF_LEN			= 0x24,
+	VFF_THRE		= 0x28,
+	VFF_WPT			= 0x2c,
+	VFF_RPT			= 0x30,
+	VFF_VALID_SIZE		= 0x3c,
+	VFF_LEFT_SIZE		= 0x40,
+	VFF_DEBUG_STATUS	= 0x50,
+};
+
+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_desc *
+to_mtk_dma_desc(struct dma_async_tx_descriptor *t)
+{
+	return container_of(t, struct mtk_desc, vd.tx);
+}
+
+static void
+mtk_dma_chan_write(struct mtk_chan *c, unsigned int reg, unsigned int val)
+{
+	writel(val, c->channel_base + reg);
+}
+
+static unsigned int mtk_dma_chan_read(struct mtk_chan *c, unsigned int reg)
+{
+	return readl(c->channel_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);
+
+	spin_lock(&c->lock);
+	if (c->desc != NULL) {
+		kfree(c->desc);
+		c->desc = NULL;
+
+		if (c->cfg.direction == DMA_DEV_TO_MEM)
+			atomic_dec(&c->entry);
+	}
+	spin_unlock(&c->lock);
+}
+
+static int mtk_dma_clk_enable(struct mtk_dmadev *mtkd)
+{
+	int rc;
+
+	rc = clk_prepare_enable(mtkd->clk);
+	if (rc)
+		dev_err(mtkd->ddev.dev, "Couldn't enable the clock\n");
+
+	return rc;
+}
+
+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)) {
+		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, int timeout)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+
+	if (mtk_dma_chan_read(c, VFF_FLUSH) == 0) {
+		mtk_dma_chan_write(c, VFF_FLUSH, VFF_FLUSH_B);
+		if (atomic_dec_and_test(&c->loopcnt))
+			complete(&c->done);
+	}
+}
+
+static int mtk_dma_tx_write(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct timespec a, b;
+	int txcount = c->remain_size;
+	unsigned int tx_size = c->cfg.dst_addr_width*1024;
+	unsigned int len, left;
+	unsigned int wpt;
+	ktime_t begin, end;
+
+	if (atomic_inc_and_test(&c->entry) > 1) {
+		if (vchan_issue_pending(&c->vc) && !c->desc) {
+			spin_lock(&mtkd->lock);
+			list_add_tail(&c->node, &mtkd->pending);
+			spin_unlock(&mtkd->lock);
+			tasklet_schedule(&mtkd->task);
+		}
+	} else {
+		while (mtk_dma_chan_read(c, VFF_LEFT_SIZE) >= c->trig) {
+			left = tx_size - mtk_dma_chan_read(c, VFF_VALID_SIZE);
+			left = (left > 16) ? (left - 16) : (0);
+			len = left < c->remain_size ? left : c->remain_size;
+
+			begin = ktime_get();
+			a = ktime_to_timespec(begin);
+			while (len--) {
+				/*
+				 * DMA limitation.
+				 * Workaround: Polling flush bit to zero,
+				 * set 1s timeout
+				 */
+				while (mtk_dma_chan_read(c, VFF_FLUSH)) {
+					end = ktime_get();
+					b = ktime_to_timespec(end);
+					if ((b.tv_sec - a.tv_sec) > 1 ||
+						((b.tv_sec - a.tv_sec) == 1 &&
+						b.tv_nsec > a.tv_nsec)) {
+						dev_info(chan->device->dev,
+							"[UART] Polling flush timeout\n");
+						return 0;
+					}
+				}
+
+				wpt = mtk_dma_chan_read(c, VFF_WPT);
+
+				if ((wpt & 0x0000ffffl) ==
+					(mtk_dma_chan_read(c, VFF_LEN) - 1))
+					mtk_dma_chan_write(c, VFF_WPT,
+								(~wpt)&0x10000);
+				else
+					mtk_dma_chan_write(c, VFF_WPT, wpt+1);
+				c->remain_size--;
+			}
+			if (c->remain_size == 0)
+				break;
+		}
+
+		if (txcount != c->remain_size) {
+			mtk_dma_chan_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+			mtk_dma_tx_flush(chan, 0);
+		}
+	}
+	atomic_dec(&c->entry);
+	return 0;
+}
+
+
+static void mtk_dma_start_tx(struct mtk_chan *c)
+{
+	if (mtk_dma_chan_read(c, VFF_LEFT_SIZE) == 0) {
+		dev_info(c->vc.chan.device->dev, "%s maybe need fix? %d @L %d\n",
+				__func__, mtk_dma_chan_read(c, VFF_LEFT_SIZE),
+				__LINE__);
+		mtk_dma_chan_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+	} else {
+		reinit_completion(&c->done);
+		atomic_inc(&c->loopcnt);
+		atomic_inc(&c->loopcnt);
+		mtk_dma_tx_write(&c->vc.chan);
+	}
+	c->paused = false;
+}
+
+static void mtk_dma_get_dst_pos(struct mtk_chan *c)
+{
+	int count;
+	unsigned int rxptr, txptr, txreg, rxreg;
+	size_t rx_size;
+
+	rx_size = c->cfg.src_addr_width*1024;
+
+	rxreg = mtk_dma_chan_read(c, VFF_RPT);
+	txreg = mtk_dma_chan_read(c, VFF_WPT);
+	rxptr = rxreg & 0x0000ffffl;
+	txptr = txreg & 0x0000ffffl;
+	count = ((rxreg ^ txreg) & 0x00010000) ?
+			(txptr + rx_size - rxptr) : (txptr - rxptr);
+
+	c->remain_size = count;
+	c->rx_ptr = rxptr;
+
+	mtk_dma_chan_write(c, VFF_RPT, txreg);
+}
+
+static void mtk_dma_start_rx(struct mtk_chan *c)
+{
+	struct mtk_desc *d = c->desc;
+
+	if (mtk_dma_chan_read(c, VFF_VALID_SIZE) != 0 && c->desc != NULL) {
+		mtk_dma_get_dst_pos(c);
+		mtk_dma_remove_virt_list(d->vd.tx.cookie, &c->vc);
+		vchan_cookie_complete(&d->vd);
+	}
+}
+
+static void mtk_dma_reset(struct mtk_chan *c)
+{
+	struct timespec a, b;
+	ktime_t begin, end;
+
+	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);
+
+	begin = ktime_get();
+	a = ktime_to_timespec(begin);
+	while (mtk_dma_chan_read(c, VFF_EN)) {
+		end = ktime_get();
+		b = ktime_to_timespec(end);
+		if ((b.tv_sec - a.tv_sec) > 1 ||
+			((b.tv_sec - a.tv_sec) == 1 &&
+			b.tv_nsec > a.tv_nsec)) {
+			dev_info(c->vc.chan.device->dev,
+				"[UART] Polling VFF EN 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);
+}
+
+static void mtk_dma_stop(struct mtk_chan *c)
+{
+	int polling_cnt;
+
+	mtk_dma_chan_write(c, VFF_FLUSH, VFF_FLUSH_CLR_B);
+
+	polling_cnt = 0;
+	while (mtk_dma_chan_read(c, VFF_FLUSH))	{
+		polling_cnt++;
+		if (polling_cnt > MTK_POLLING_CNT) {
+			dev_info(c->vc.chan.device->dev, "mtk_uart_stop_dma: polling VFF_FLUSH fail VFF_DEBUG_STATUS=0x%x\n",
+					mtk_dma_chan_read(c, VFF_DEBUG_STATUS));
+			break;
+		}
+	}
+
+	polling_cnt = 0;
+	/*set stop as 1 -> wait until en is 0 -> set stop as 0*/
+	mtk_dma_chan_write(c, VFF_STOP, VFF_STOP_B);
+	while (mtk_dma_chan_read(c, VFF_EN)) {
+		polling_cnt++;
+		if (polling_cnt > MTK_POLLING_CNT) {
+			dev_info(c->vc.chan.device->dev, "mtk_uart_stop_dma: polling VFF_EN fail VFF_DEBUG_STATUS=0x%x\n",
+					mtk_dma_chan_read(c, VFF_DEBUG_STATUS));
+			break;
+		}
+	}
+	mtk_dma_chan_write(c, VFF_STOP, VFF_STOP_CLR_B);
+	mtk_dma_chan_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
+	mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_INT_FLAG_CLR_B);
+
+	c->paused = 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 mtk_chan *c;
+	struct virt_dma_desc *vd;
+	dma_cookie_t cookie;
+	LIST_HEAD(head);
+
+	spin_lock_irq(&mtkd->lock);
+	list_splice_tail_init(&mtkd->pending, &head);
+	spin_unlock_irq(&mtkd->lock);
+
+	while (!list_empty(&head)) {
+		c = list_first_entry(&head, struct mtk_chan, node);
+		cookie = c->vc.chan.cookie;
+
+		spin_lock_irq(&c->vc.lock);
+
+		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);
+		} else {
+			dev_warn(c->vc.chan.device->dev, "%s maybe error @Line%d\n",
+				__func__, __LINE__);
+		}
+		spin_unlock_irq(&c->vc.lock);
+	}
+}
+
+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;
+
+	ret = -EBUSY;
+
+	if (mtkd->lch_map[c->dma_ch] == NULL) {
+		c->channel_base = mtkd->base + 0x80 * c->dma_ch;
+		mtkd->lch_map[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 == true) {
+		c->requested = false;
+		free_irq(mtkd->irq + c->dma_ch, chan);
+	}
+
+	c->channel_base = NULL;
+	mtkd->lch_map[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;
+}
+
+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;
+
+	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) & 0x0000ffffl;
+		txstate->residue = c->rx_ptr;
+	} else if (ret == DMA_COMPLETE && c->cfg.direction == DMA_DEV_TO_MEM) {
+		txstate->residue = c->remain_size;
+	} else {
+		txstate->residue = 0;
+	}
+
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return ret;
+}
+
+static size_t mtk_dma_desc_size(struct mtk_desc *d)
+{
+	struct mtk_sg *sg;
+	unsigned int i;
+	size_t size;
+
+	for (size = i = 0; i < d->sglen; i++) {
+		sg = &d->sg[i];
+		size += sg->en * sg->fn;
+	}
+	return size;
+}
+
+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);
+	enum dma_slave_buswidth dev_width;
+	struct scatterlist *sgent;
+	struct mtk_desc *d;
+	dma_addr_t dev_addr;
+	unsigned int i, j, en, frame_bytes;
+
+	en = frame_bytes = 1;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		dev_addr = c->cfg.src_addr;
+		dev_width = c->cfg.src_addr_width;
+	} else if (dir == DMA_MEM_TO_DEV) {
+		dev_addr = c->cfg.dst_addr;
+		dev_width = c->cfg.dst_addr_width;
+	} else {
+		dev_err(chan->device->dev, "%s: bad direction?\n", __func__);
+		return NULL;
+	}
+
+	/* Now allocate and setup the descriptor. */
+	d = kmalloc(sizeof(*d) + sglen * sizeof(d->sg[0]),
+				GFP_KERNEL | ___GFP_ZERO);
+	if (!d)
+		return NULL;
+
+	d->dir = dir;
+	d->dev_addr = dev_addr;
+
+	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) / frame_bytes;
+		j++;
+	}
+
+	d->sglen = j;
+
+	if (dir == DMA_MEM_TO_DEV)
+		c->remain_size = mtk_dma_desc_size(d);
+
+	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 mtk_dmadev *mtkd;
+	struct virt_dma_desc *vd;
+	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);
+			if (atomic_read(&c->entry) > 0)
+				atomic_set(&c->entry, 0);
+		}
+	} 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, 0x03);
+
+	if (!(atomic_add_return(1, &c->entry) > 1))
+		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_chan *c = to_mtk_dma_chan(chan);
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(chan->device);
+	struct mtk_desc *d = c->desc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+
+	if (c->remain_size != 0) {
+		/* maybe never can't enter*/
+		dev_warn(chan->device->dev, "%s errrrrr---remain[%d]-----%d--\n",
+			__func__, (int)c->remain_size, __LINE__);
+		spin_lock(&mtkd->lock);
+		list_add_tail(&c->node, &mtkd->pending);
+		spin_unlock(&mtkd->lock);
+		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_INT_FLAG_CLR_B);
+
+	if (atomic_dec_and_test(&c->loopcnt))
+		complete(&c->done);
+
+	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;
+
+	memcpy(&c->cfg, cfg, sizeof(c->cfg));
+
+	if (cfg->direction == DMA_DEV_TO_MEM) {
+		mtk_dma_chan_write(c, VFF_ADDR, cfg->src_addr);
+		mtk_dma_chan_write(c, VFF_LEN, cfg->src_addr_width*1024);
+		mtk_dma_chan_write(c, VFF_THRE,
+					VFF_RX_THRE(cfg->src_addr_width*1024));
+		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_INT_FLAG_CLR_B);
+		mtk_dma_chan_write(c, VFF_EN, VFF_EN_B);
+
+		if (c->requested == false) {
+			atomic_set(&c->entry, 0);
+			c->requested = true;
+			ret = request_irq(mtkd->irq + c->dma_ch,
+						mtk_dma_rx_interrupt,
+						IRQF_TRIGGER_NONE,
+						DRV_NAME, chan);
+			if (ret) {
+				dev_err(chan->device->dev, "Cannot request IRQ\n");
+				return IRQ_NONE;
+			}
+		}
+	} else if (cfg->direction == DMA_MEM_TO_DEV)	{
+		mtk_dma_chan_write(c, VFF_ADDR, cfg->dst_addr);
+		mtk_dma_chan_write(c, VFF_LEN, cfg->dst_addr_width*1024);
+		mtk_dma_chan_write(c, VFF_THRE,
+					VFF_TX_THRE(cfg->dst_addr_width*1024));
+		mtk_dma_chan_write(c, VFF_INT_FLAG, VFF_INT_FLAG_CLR_B);
+		mtk_dma_chan_write(c, VFF_EN, VFF_EN_B);
+
+		if (c->requested == false) {
+			c->requested = true;
+			ret = request_irq(mtkd->irq + c->dma_ch,
+						mtk_dma_tx_interrupt,
+						IRQF_TRIGGER_NONE,
+						DRV_NAME, chan);
+			if (ret) {
+				dev_err(chan->device->dev, "Cannot request IRQ\n");
+				return IRQ_NONE;
+			}
+		}
+	}
+
+	if (mtk_dma_chan_read(c, VFF_EN) != VFF_EN_B) {
+		dev_err(chan->device->dev, "Start DMA fail\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int mtk_dma_terminate_all(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_dma_chan(chan);
+	struct mtk_dmadev *mtkd = to_mtk_dma_dev(c->vc.chan.device);
+	unsigned long flags;
+	LIST_HEAD(head);
+
+	if (atomic_read(&c->loopcnt) != 0)
+		wait_for_completion(&c->done);
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+
+	/* Prevent this channel being scheduled */
+	spin_lock(&mtkd->lock);
+	list_del_init(&c->node);
+	spin_unlock(&mtkd->lock);
+
+	if (c->desc) {
+		mtk_dma_remove_virt_list(c->desc->vd.tx.cookie, &c->vc);
+		mtk_dma_desc_free(&c->desc->vd);
+		if (!c->paused)
+			mtk_dma_stop(c);
+	}
+
+	vchan_get_all_descriptors(&c->vc, &head);
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+	vchan_dma_desc_free_list(&c->vc, &head);
+
+	return 0;
+}
+
+static int mtk_dma_pause(struct dma_chan *chan)
+{
+	/* Pause/Resume only allowed with cyclic mode */
+	return -EINVAL;
+}
+
+static int mtk_dma_resume(struct dma_chan *chan)
+{
+	/* Pause/Resume only allowed with cyclic mode */
+	return -EINVAL;
+}
+
+static int mtk_dma_chan_init(struct mtk_dmadev *mtkd)
+{
+	struct mtk_chan *c;
+
+	c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
+	if (!c)
+		return -ENOMEM;
+
+	c->vc.desc_free = mtk_dma_desc_free;
+	vchan_init(&c->vc, &mtkd->ddev);
+	spin_lock_init(&c->lock);
+	INIT_LIST_HEAD(&c->node);
+
+	init_completion(&c->done);
+	atomic_set(&c->loopcnt, 0);
+	atomic_set(&c->entry, 0);
+
+	return 0;
+}
+
+static void mtk_dma_free(struct mtk_dmadev *mtkd)
+{
+	tasklet_kill(&mtkd->task);
+	while (!list_empty(&mtkd->ddev.channels)) {
+		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_dma_probe(struct platform_device *pdev)
+{
+	struct mtk_dmadev *mtkd;
+	struct resource *res;
+	int rc, i;
+
+	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	if (rc)
+		return rc;
+
+	mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
+	if (!mtkd)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+	mtkd->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(mtkd->base))
+		return PTR_ERR(mtkd->base);
+
+	mtkd->irq = platform_get_irq(pdev, 0);
+	if (mtkd->irq < 0) {
+		dev_err(&pdev->dev, "Cannot claim IRQ\n");
+		return mtkd->irq;
+	}
+
+	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);
+	}
+
+	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_pause;
+	mtkd->ddev.device_resume = mtk_dma_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_BURST;
+	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_SDMA_REQUESTS;
+	if (pdev->dev.of_node && 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_SDMA_REQUESTS);
+	}
+
+	for (i = 0; i < MTK_SDMA_CHANNELS; i++) {
+		rc = mtk_dma_chan_init(mtkd);
+		if (rc) {
+			mtk_dma_free(mtkd);
+			return rc;
+		}
+	}
+
+	rc = mtk_dma_clk_enable(mtkd);
+	if (rc) {
+		pr_warn("MTK-UART-DMA: enable clk failed: %d\n",
+			rc);
+		mtk_dma_free(mtkd);
+		return rc;
+	}
+
+	rc = dma_async_device_register(&mtkd->ddev);
+	if (rc) {
+		pr_warn("MTK-UART-DMA: failed to register slave DMA engine device: %d\n",
+			rc);
+		mtk_dma_clk_disable(mtkd);
+		mtk_dma_free(mtkd);
+		return rc;
+	}
+
+	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) {
+			pr_warn("MTK-UART-DMA: failed to register DMA controller\n");
+			dma_async_device_unregister(&mtkd->ddev);
+			mtk_dma_clk_disable(mtkd);
+			mtk_dma_free(mtkd);
+		}
+	}
+
+	return rc;
+}
+
+static int mtk_dma_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);
+
+	mtk_dma_clk_disable(mtkd);
+
+	dma_async_device_unregister(&mtkd->ddev);
+
+	mtk_dma_free(mtkd);
+
+	return 0;
+}
+
+static struct platform_driver mtk_dma_driver = {
+	.probe	= mtk_dma_probe,
+	.remove	= mtk_dma_remove,
+	.driver = {
+		.name = "mtk-uart-dma-engine",
+		.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 = (int)req;
+			return true;
+		}
+	}
+	return false;
+}
+
+static int mtk_dma_init(void)
+{
+	return platform_driver_register(&mtk_dma_driver);
+}
+subsys_initcall(mtk_dma_init);
+
+static void __exit mtk_dma_exit(void)
+{
+	platform_driver_unregister(&mtk_dma_driver);
+}
+module_exit(mtk_dma_exit);
+
+MODULE_DESCRIPTION("MediaTek MTK APDMA Controller Driver");
+MODULE_AUTHOR("Long Cheng (Long) <long.cheng@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+
-- 
1.7.9.5