[PATCH v2 0/3] serial: mxs-auart: add DMA support for auart in mx28

[PATCH v2 0/3] serial: mxs-auart: add DMA support for auart in mx28

[Huang Shijie]

This patch set adds the DMA support for auart in mx28.
patch 1:
	In mx23, the DMA has a bug(see errata:2836). We can not add the
	DMA support in mx23, but we can add DMA support to auart in mx28.
	So in order to add the DMA support for the auart in mx28, we should add
	the platform_device_id to distinguish the distinguish SOCs.

patch 2: add the DMA support for mx28
	Only we meet the following conditions, we can enable the DMA support
	for auart:
        (1) We enable the DMA support in the dts file, such as
            arch/arm/boot/dts/imx28.dtsi.
        (2) We enable the hardware flow control.
        (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
            we can not add the DMA support to mx23.

patch 3: enable the DMA support in dts for mx28 
	You can use the /ttyAPP0 to test this patch set. 
	I tested this patch in mx28-evk board.

v1 --> v2:
	[1] use the inline function, not a macro, to distinguish the SOCs.
	[2] remove the "inline" for mxs_auart_tx_chars().
	[3] use the `pio`, not the `pio[1]` to fill the DMA descriptor.
	[4] use bit operation to serialize the DMA TX.
	[5] use the RX/TX DMA channel to enable the DMA support, remove the
	    "fsl,auart-enable-dma".

Huang Shijie (3):
  serial: mxs-auart: distinguish the different SOCs
  serial: mxs-auart: add the DMA support for mx28
  ARM: dts: enable dma support for auart0 in mx28

 .../bindings/tty/serial/fsl-mxs-auart.txt          |    8 +
 arch/arm/boot/dts/imx28.dtsi                       |    1 +
 drivers/tty/serial/mxs-auart.c                     |  360 +++++++++++++++++++-
 3 files changed, 358 insertions(+), 11 deletions(-)

[PATCH v2 1/3] serial: mxs-auart: distinguish the different SOCs

[Huang Shijie]

The current mxs-auart driver is used for both mx23 and mx28.

But in mx23, the DMA has a bug(see errata:2836). We can not add the
DMA support in mx23, but we can add DMA support to auart in mx28.

So in order to add the DMA support for the auart in mx28, we should
distinguish the distinguish SOCs.

This patch adds a new platform_device_id table and a inline function
is_imx28_auart() to distinguish the mx23 and mx28.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 drivers/tty/serial/mxs-auart.c |   42 ++++++++++++++++++++++++++++++++++-----
 1 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 6db3baa..06d7271 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -114,11 +114,17 @@
 
 static struct uart_driver auart_driver;
 
+enum mxs_auart_type {
+	IMX23_AUART,
+	IMX28_AUART,
+};
+
 struct mxs_auart_port {
 	struct uart_port port;
 
 	unsigned int flags;
 	unsigned int ctrl;
+	enum mxs_auart_type devtype;
 
 	unsigned int irq;
 
@@ -126,6 +132,29 @@ struct mxs_auart_port {
 	struct device *dev;
 };
 
+static struct platform_device_id mxs_auart_devtype[] = {
+	{ .name = "mxs-auart-imx23", .driver_data = IMX23_AUART },
+	{ .name = "mxs-auart-imx28", .driver_data = IMX28_AUART },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, mxs_auart_devtype);
+
+static struct of_device_id mxs_auart_dt_ids[] = {
+	{
+		.compatible = "fsl,imx28-auart",
+		.data = &mxs_auart_devtype[IMX28_AUART]
+	}, {
+		.compatible = "fsl,imx23-auart",
+		.data = &mxs_auart_devtype[IMX23_AUART]
+	}, { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mxs_auart_dt_ids);
+
+static inline int is_imx28_auart(struct mxs_auart_port *s)
+{
+	return s->devtype == IMX28_AUART;
+}
+
 static void mxs_auart_stop_tx(struct uart_port *u);
 
 #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)
@@ -706,6 +735,8 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
 
 static int __devinit mxs_auart_probe(struct platform_device *pdev)
 {
+	const struct of_device_id *of_id =
+			of_match_device(mxs_auart_dt_ids, &pdev->dev);
 	struct mxs_auart_port *s;
 	u32 version;
 	int ret = 0;
@@ -730,6 +761,11 @@ static int __devinit mxs_auart_probe(struct platform_device *pdev)
 		goto out_free;
 	}
 
+	if (of_id) {
+		pdev->id_entry = of_id->data;
+		s->devtype = pdev->id_entry->driver_data;
+	}
+
 	s->clk = clk_get(&pdev->dev, NULL);
 	if (IS_ERR(s->clk)) {
 		ret = PTR_ERR(s->clk);
@@ -805,12 +841,6 @@ static int __devexit mxs_auart_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static struct of_device_id mxs_auart_dt_ids[] = {
-	{ .compatible = "fsl,imx23-auart", },
-	{ /* sentinel */ }
-};
-MODULE_DEVICE_TABLE(of, mxs_auart_dt_ids);
-
 static struct platform_driver mxs_auart_driver = {
 	.probe = mxs_auart_probe,
 	.remove = __devexit_p(mxs_auart_remove),
-- 
1.7.0.4

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

Only we meet the following conditions, we can enable the DMA support for
auart:

  (1) We enable the DMA support in the dts file, such as
      arch/arm/boot/dts/imx28.dtsi.

  (2) We enable the hardware flow control.

  (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
      we can not add the DMA support to mx23.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 .../bindings/tty/serial/fsl-mxs-auart.txt          |    8 +
 drivers/tty/serial/mxs-auart.c                     |  318 +++++++++++++++++++-
 2 files changed, 321 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
index 2ee903f..273a8d5 100644
--- a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
+++ b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
@@ -6,11 +6,19 @@ Required properties:
 - reg : Address and length of the register set for the device
 - interrupts : Should contain the auart interrupt numbers
 
+Optional properties:
+- fsl,auart-dma-channel : The DMA channels, the first is for RX, the other
+		is for TX. If you add this property, it also means that you
+		will enable the DMA support for the auart.
+		Note: due to the hardware bug in imx23(see errata : 2836),
+		only the imx28 can enable the DMA support for the auart.
+
 Example:
 auart0: serial at 8006a000 {
 	compatible = "fsl,imx28-auart", "fsl,imx23-auart";
 	reg = <0x8006a000 0x2000>;
 	interrupts = <112 70 71>;
+	fsl,auart-dma-channel = <8 9>;
 };
 
 Note: Each auart port should have an alias correctly numbered in "aliases"
diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 06d7271..d593e0a 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -34,6 +34,8 @@
 #include <linux/io.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/of_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/fsl/mxs-dma.h>
 
 #include <asm/cacheflush.h>
 
@@ -71,6 +73,15 @@
 
 #define AUART_CTRL0_SFTRST			(1 << 31)
 #define AUART_CTRL0_CLKGATE			(1 << 30)
+#define AUART_CTRL0_RXTO_ENABLE			(1 << 27)
+#define AUART_CTRL0_RXTIMEOUT(v)		(((v) & 0x7ff) << 16)
+#define AUART_CTRL0_XFER_COUNT(v)		((v) & 0xffff)
+
+#define AUART_CTRL1_XFER_COUNT(v)		((v) & 0xffff)
+
+#define AUART_CTRL2_DMAONERR			(1 << 26)
+#define AUART_CTRL2_TXDMAE			(1 << 25)
+#define AUART_CTRL2_RXDMAE			(1 << 24)
 
 #define AUART_CTRL2_CTSEN			(1 << 15)
 #define AUART_CTRL2_RTSEN			(1 << 14)
@@ -111,6 +122,7 @@
 #define AUART_STAT_BERR				(1 << 18)
 #define AUART_STAT_PERR				(1 << 17)
 #define AUART_STAT_FERR				(1 << 16)
+#define AUART_STAT_RXCOUNT_MASK			0xffff
 
 static struct uart_driver auart_driver;
 
@@ -122,7 +134,10 @@ enum mxs_auart_type {
 struct mxs_auart_port {
 	struct uart_port port;
 
-	unsigned int flags;
+#define MXS_AUART_DMA_CONFIG	0x1
+#define MXS_AUART_DMA_ENABLED	0x2
+#define MXS_AUART_DMA_TX_SYNC	2  /* bit 2 */
+	unsigned long flags;
 	unsigned int ctrl;
 	enum mxs_auart_type devtype;
 
@@ -130,6 +145,20 @@ struct mxs_auart_port {
 
 	struct clk *clk;
 	struct device *dev;
+
+	/* for DMA */
+	struct mxs_dma_data dma_data;
+	int dma_channel_rx, dma_channel_tx;
+	int dma_irq_rx, dma_irq_tx;
+	int dma_channel;
+
+	struct scatterlist tx_sgl;
+	struct dma_chan	*tx_dma_chan;
+	void *tx_dma_buf;
+
+	struct scatterlist rx_sgl;
+	struct dma_chan	*rx_dma_chan;
+	void *rx_dma_buf;
 };
 
 static struct platform_device_id mxs_auart_devtype[] = {
@@ -155,14 +184,107 @@ static inline int is_imx28_auart(struct mxs_auart_port *s)
 	return s->devtype == IMX28_AUART;
 }
 
+static inline bool auart_dma_enabled(struct mxs_auart_port *s)
+{
+	return s->flags & MXS_AUART_DMA_ENABLED;
+}
+
 static void mxs_auart_stop_tx(struct uart_port *u);
 
 #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)
 
-static inline void mxs_auart_tx_chars(struct mxs_auart_port *s)
+static void mxs_auart_tx_chars(struct mxs_auart_port *s);
+
+static void dma_tx_callback(void *param)
 {
+	struct mxs_auart_port *s = param;
 	struct circ_buf *xmit = &s->port.state->xmit;
 
+	dma_unmap_sg(s->dev, &s->tx_sgl, 1, DMA_TO_DEVICE);
+
+	/* clear the bit used to serialize the DMA tx. */
+	clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
+	smp_mb__after_clear_bit();
+
+	/* wake up the possible processes. */
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&s->port);
+
+	mxs_auart_tx_chars(s);
+}
+
+static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
+{
+	struct dma_async_tx_descriptor *desc;
+	struct scatterlist *sgl = &s->tx_sgl;
+	struct dma_chan *channel = s->tx_dma_chan;
+	u32 pio;
+
+	/* [1] : send PIO. Note, the first pio word is CTRL1. */
+	pio = AUART_CTRL1_XFER_COUNT(size);
+	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
+					1, DMA_TRANS_NONE, 0);
+	if (!desc) {
+		dev_err(s->dev, "step 1 error\n");
+		return -EINVAL;
+	}
+
+	/* [2] : set DMA buffer. */
+	sg_init_one(sgl, s->tx_dma_buf, size);
+	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
+	desc = dmaengine_prep_slave_sg(channel, sgl,
+			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!desc) {
+		dev_err(s->dev, "step 2 error\n");
+		return -EINVAL;
+	}
+
+	/* [3] : submit the DMA */
+	desc->callback = dma_tx_callback;
+	desc->callback_param = s;
+	dmaengine_submit(desc);
+	dma_async_issue_pending(channel);
+	return 0;
+}
+
+static void mxs_auart_tx_chars(struct mxs_auart_port *s)
+{
+	struct circ_buf *xmit = &s->port.state->xmit;
+
+	if (auart_dma_enabled(s)) {
+		int i = 0;
+		int size;
+		void *buffer = s->tx_dma_buf;
+
+		if (test_and_set_bit(MXS_AUART_DMA_TX_SYNC, &s->flags))
+			return;
+
+		while (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
+			size = min_t(u32, UART_XMIT_SIZE - i,
+				     CIRC_CNT_TO_END(xmit->head,
+						     xmit->tail,
+						     UART_XMIT_SIZE));
+			memcpy(buffer + i, xmit->buf + xmit->tail, size);
+			xmit->tail = (xmit->tail + size) & (UART_XMIT_SIZE - 1);
+
+			i += size;
+			if (i >= UART_XMIT_SIZE)
+				break;
+		}
+
+		if (uart_tx_stopped(&s->port))
+			mxs_auart_stop_tx(&s->port);
+
+		if (i) {
+			mxs_auart_dma_tx(s, i);
+		} else {
+			clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
+			smp_mb__after_clear_bit();
+		}
+		return;
+	}
+
+
 	while (!(readl(s->port.membase + AUART_STAT) &
 		 AUART_STAT_TXFF)) {
 		if (s->port.x_char) {
@@ -316,10 +438,155 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
 	return mctrl;
 }
 
+static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
+{
+	struct mxs_auart_port *s = param;
+
+	if (!mxs_dma_is_apbx(chan))
+		return false;
+
+	if (s->dma_channel == chan->chan_id) {
+		chan->private = &s->dma_data;
+		return true;
+	}
+	return false;
+}
+
+static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
+static void dma_rx_callback(void *arg)
+{
+	struct mxs_auart_port *s = (struct mxs_auart_port *) arg;
+	struct tty_struct *tty = s->port.state->port.tty;
+	int count;
+	u32 stat;
+
+	stat = readl(s->port.membase + AUART_STAT);
+	stat &= ~(AUART_STAT_OERR | AUART_STAT_BERR |
+			AUART_STAT_PERR | AUART_STAT_FERR);
+
+	count = stat & AUART_STAT_RXCOUNT_MASK;
+	tty_insert_flip_string(tty, s->rx_dma_buf, count);
+
+	writel(stat, s->port.membase + AUART_STAT);
+	tty_flip_buffer_push(tty);
+
+	/* start the next DMA for RX. */
+	mxs_auart_dma_prep_rx(s);
+}
+
+static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s)
+{
+	struct dma_async_tx_descriptor *desc;
+	struct scatterlist *sgl = &s->rx_sgl;
+	struct dma_chan *channel = s->rx_dma_chan;
+	u32 pio[1];
+
+	/* [1] : send PIO */
+	pio[0] = AUART_CTRL0_RXTO_ENABLE
+		| AUART_CTRL0_RXTIMEOUT(0x80)
+		| AUART_CTRL0_XFER_COUNT(UART_XMIT_SIZE);
+	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
+					1, DMA_TRANS_NONE, 0);
+	if (!desc) {
+		dev_err(s->dev, "step 1 error\n");
+		return -EINVAL;
+	}
+
+	/* [2] : send DMA request */
+	sg_init_one(sgl, s->rx_dma_buf, UART_XMIT_SIZE);
+	dma_map_sg(s->dev, sgl, 1, DMA_FROM_DEVICE);
+	desc = dmaengine_prep_slave_sg(channel, sgl, 1, DMA_DEV_TO_MEM,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!desc) {
+		dev_err(s->dev, "step 2 error\n");
+		return -1;
+	}
+
+	/* [3] : submit the DMA, but do not issue it. */
+	desc->callback = dma_rx_callback;
+	desc->callback_param = s;
+	dmaengine_submit(desc);
+	dma_async_issue_pending(channel);
+	return 0;
+}
+
+static void mxs_auart_dma_exit_channel(struct mxs_auart_port *s)
+{
+	if (s->tx_dma_chan) {
+		dma_release_channel(s->tx_dma_chan);
+		s->tx_dma_chan = NULL;
+	}
+	if (s->rx_dma_chan) {
+		dma_release_channel(s->rx_dma_chan);
+		s->rx_dma_chan = NULL;
+	}
+
+	kfree(s->tx_dma_buf);
+	kfree(s->rx_dma_buf);
+	s->tx_dma_buf = NULL;
+	s->rx_dma_buf = NULL;
+}
+
+static void mxs_auart_dma_exit(struct mxs_auart_port *s)
+{
+
+	writel(AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE | AUART_CTRL2_DMAONERR,
+		s->port.membase + AUART_CTRL2_CLR);
+
+	mxs_auart_dma_exit_channel(s);
+	s->flags &= ~MXS_AUART_DMA_ENABLED;
+}
+
+static int mxs_auart_dma_init(struct mxs_auart_port *s)
+{
+	dma_cap_mask_t mask;
+
+	if (auart_dma_enabled(s))
+		return 0;
+
+	/* We do not get the right DMA channels. */
+	if (s->dma_channel_rx == -1 || s->dma_channel_rx == -1)
+		return -EINVAL;
+
+	/* init for RX */
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+	s->dma_channel = s->dma_channel_rx;
+	s->dma_data.chan_irq = s->dma_irq_rx;
+	s->rx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
+	if (!s->rx_dma_chan)
+		goto err_out;
+	s->rx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
+	if (!s->rx_dma_buf)
+		goto err_out;
+
+	/* init for TX */
+	s->dma_channel = s->dma_channel_tx;
+	s->dma_data.chan_irq = s->dma_irq_tx;
+	s->tx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
+	if (!s->tx_dma_chan)
+		goto err_out;
+	s->tx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
+	if (!s->tx_dma_buf)
+		goto err_out;
+
+	/* set the flags */
+	s->flags |= MXS_AUART_DMA_ENABLED;
+	dev_dbg(s->dev, "enabled the DMA support.");
+
+	return 0;
+
+err_out:
+	mxs_auart_dma_exit_channel(s);
+	return -EINVAL;
+
+}
+
 static void mxs_auart_settermios(struct uart_port *u,
 				 struct ktermios *termios,
 				 struct ktermios *old)
 {
+	struct mxs_auart_port *s = to_auart_port(u);
 	u32 bm, ctrl, ctrl2, div;
 	unsigned int cflag, baud;
 
@@ -391,10 +658,23 @@ static void mxs_auart_settermios(struct uart_port *u,
 		ctrl |= AUART_LINECTRL_STP2;
 
 	/* figure out the hardware flow control settings */
-	if (cflag & CRTSCTS)
+	if (cflag & CRTSCTS) {
+		/*
+		 * The DMA has a bug(see errata:2836) in mx23.
+		 * So we can not implement the DMA for auart in mx23,
+		 * we can only implement the DMA support for auart
+		 * in mx28.
+		 */
+		if (is_imx28_auart(s) && (s->flags & MXS_AUART_DMA_CONFIG)) {
+			if (!mxs_auart_dma_init(s))
+				/* enable DMA tranfer */
+				ctrl2 |= AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE
+				       | AUART_CTRL2_DMAONERR;
+		}
 		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
-	else
+	} else {
 		ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
+	}
 
 	/* set baud rate */
 	baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);
@@ -406,6 +686,17 @@ static void mxs_auart_settermios(struct uart_port *u,
 	writel(ctrl2, u->membase + AUART_CTRL2);
 
 	uart_update_timeout(u, termios->c_cflag, baud);
+
+	/* prepare for the DMA RX. */
+	if (auart_dma_enabled(s)) {
+		if (!mxs_auart_dma_prep_rx(s)) {
+			/* Disable the normal RX interrupt. */
+			writel(AUART_INTR_RXIEN, u->membase + AUART_INTR_CLR);
+		} else {
+			mxs_auart_dma_exit(s);
+			dev_err(s->dev, "We can not start up the DMA.\n");
+		}
+	}
 }
 
 static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
@@ -484,6 +775,9 @@ static void mxs_auart_shutdown(struct uart_port *u)
 {
 	struct mxs_auart_port *s = to_auart_port(u);
 
+	if (auart_dma_enabled(s))
+		mxs_auart_dma_exit(s);
+
 	writel(AUART_CTRL2_UARTEN, u->membase + AUART_CTRL2_CLR);
 
 	writel(AUART_INTR_RXIEN | AUART_INTR_RTIEN | AUART_INTR_CTSMIEN,
@@ -717,6 +1011,7 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
 		struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
+	u32 dma_channel[2];
 	int ret;
 
 	if (!np)
@@ -730,6 +1025,20 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
 	}
 	s->port.line = ret;
 
+	s->dma_irq_rx = platform_get_irq(pdev, 1);
+	s->dma_irq_tx = platform_get_irq(pdev, 2);
+
+	ret = of_property_read_u32_array(np, "fsl,auart-dma-channel",
+					dma_channel, 2);
+	if (ret == 0) {
+		s->dma_channel_rx = dma_channel[0];
+		s->dma_channel_tx = dma_channel[1];
+
+		s->flags |= MXS_AUART_DMA_CONFIG;
+	} else {
+		s->dma_channel_rx = -1;
+		s->dma_channel_tx = -1;
+	}
 	return 0;
 }
 
@@ -787,7 +1096,6 @@ static int __devinit mxs_auart_probe(struct platform_device *pdev)
 	s->port.type = PORT_IMX;
 	s->port.dev = s->dev = get_device(&pdev->dev);
 
-	s->flags = 0;
 	s->ctrl = 0;
 
 	s->irq = platform_get_irq(pdev, 0);
-- 
1.7.0.4

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Vinod Koul]

On Wed, 2012-10-24 at 18:27 +0800, Huang Shijie wrote:
> Only we meet the following conditions, we can enable the DMA support for
> auart:
> 
>   (1) We enable the DMA support in the dts file, such as
>       arch/arm/boot/dts/imx28.dtsi.
> 
>   (2) We enable the hardware flow control.
> 
>   (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
>       we can not add the DMA support to mx23.
> 
> Signed-off-by: Huang Shijie <b32955@freescale.com>

>  
>  #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)

> +
> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
> +{
> +	struct dma_async_tx_descriptor *desc;
> +	struct scatterlist *sgl = &s->tx_sgl;
> +	struct dma_chan *channel = s->tx_dma_chan;
> +	u32 pio;
> +
> +	/* [1] : send PIO. Note, the first pio word is CTRL1. */
> +	pio = AUART_CTRL1_XFER_COUNT(size);
> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
> +					1, DMA_TRANS_NONE, 0);
this seems like a hack. API expects a scatterlist as argument.
Same thing about direction, NONE doesnt mean anything for dma transfer.
> +	if (!desc) {
> +		dev_err(s->dev, "step 1 error\n");
> +		return -EINVAL;
> +	}
> +
> +	/* [2] : set DMA buffer. */
> +	sg_init_one(sgl, s->tx_dma_buf, size);
> +	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
> +	desc = dmaengine_prep_slave_sg(channel, sgl,
> +			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +	if (!desc) {
> +		dev_err(s->dev, "step 2 error\n");
> +		return -EINVAL;
> +	}
> +
> +	/* [3] : submit the DMA */
> +	desc->callback = dma_tx_callback;
> +	desc->callback_param = s;
> +	dmaengine_submit(desc);
> +	dma_async_issue_pending(channel);
> +	return 0;
> +}
> +

>  
> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
> +{
> +	struct mxs_auart_port *s = param;
> +
> +	if (!mxs_dma_is_apbx(chan))
> +		return false;
> +
> +	if (s->dma_channel == chan->chan_id) {
> +		chan->private = &s->dma_data;
dont use chan->private. You need to dmaengine_slave_config API

> +		return true;
> +	}
> +	return false;
> +}
> +

-- 
Vinod Koul
Intel Corp.

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

? 2012?10?25? 12:18, Vinod Koul ??:
>
>> +
>> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
>> +{
>> +	struct dma_async_tx_descriptor *desc;
>> +	struct scatterlist *sgl =&s->tx_sgl;
>> +	struct dma_chan *channel = s->tx_dma_chan;
>> +	u32 pio;
>> +
>> +	/* [1] : send PIO. Note, the first pio word is CTRL1. */
>> +	pio = AUART_CTRL1_XFER_COUNT(size);
>> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
>> +					1, DMA_TRANS_NONE, 0);
> this seems like a hack. API expects a scatterlist as argument.
> Same thing about direction, NONE doesnt mean anything for dma transfer.
It's not a hack. this DMA descriptor is used to set the registers.
Please see the code in drivers/dma/mxs-dma.c:mxs_dam_prep_slave_sg().


>> +	if (!desc) {
>> +		dev_err(s->dev, "step 1 error\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	/* [2] : set DMA buffer. */
>> +	sg_init_one(sgl, s->tx_dma_buf, size);
>> +	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
>> +	desc = dmaengine_prep_slave_sg(channel, sgl,
>> +			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>> +	if (!desc) {
>> +		dev_err(s->dev, "step 2 error\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	/* [3] : submit the DMA */
>> +	desc->callback = dma_tx_callback;
>> +	desc->callback_param = s;
>> +	dmaengine_submit(desc);
>> +	dma_async_issue_pending(channel);
>> +	return 0;
>> +}
>> +
>>
>> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
>> +{
>> +	struct mxs_auart_port *s = param;
>> +
>> +	if (!mxs_dma_is_apbx(chan))
>> +		return false;
>> +
>> +	if (s->dma_channel == chan->chan_id) {
>> +		chan->private =&s->dma_data;
> dont use chan->private. You need to dmaengine_slave_config API
please see the drivers/dma/mxs-dma.c:mxs_dam_alloc_chan_resoures().

The mxs-dma driver uses ->private to store the channel interrupt number.

thanks
Huang Shijie
>> +		return true;
>> +	}
>> +	return false;
>> +}
>> +

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Vinod Koul]

On Thu, 2012-10-25 at 13:50 +0800, Huang Shijie wrote:
> ? 2012?10?25? 12:18, Vinod Koul ??:
> >
> >> +
> >> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
> >> +{
> >> +	struct dma_async_tx_descriptor *desc;
> >> +	struct scatterlist *sgl =&s->tx_sgl;
> >> +	struct dma_chan *channel = s->tx_dma_chan;
> >> +	u32 pio;
> >> +
> >> +	/* [1] : send PIO. Note, the first pio word is CTRL1. */
> >> +	pio = AUART_CTRL1_XFER_COUNT(size);
> >> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
> >> +					1, DMA_TRANS_NONE, 0);
> > this seems like a hack. API expects a scatterlist as argument.
> > Same thing about direction, NONE doesnt mean anything for dma transfer.
> It's not a hack. this DMA descriptor is used to set the registers.
> Please see the code in drivers/dma/mxs-dma.c:mxs_dam_prep_slave_sg().
yes it is, and also an abuse of the api.
prep_slave_sg() expects a scatter list and you are passing something
else and using DMA_TRANS_NONE to do that, which makes no sense!!!

If you have to setup your registers you need to setup based on what APIs
passed you and not by abusing.

> >> +	if (!desc) {
> >> +		dev_err(s->dev, "step 1 error\n");
> >> +		return -EINVAL;
> >> +	}
> >> +
> >> +	/* [2] : set DMA buffer. */
> >> +	sg_init_one(sgl, s->tx_dma_buf, size);
> >> +	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
> >> +	desc = dmaengine_prep_slave_sg(channel, sgl,
> >> +			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> >> +	if (!desc) {
> >> +		dev_err(s->dev, "step 2 error\n");
> >> +		return -EINVAL;
> >> +	}
> >> +
> >> +	/* [3] : submit the DMA */
> >> +	desc->callback = dma_tx_callback;
> >> +	desc->callback_param = s;
> >> +	dmaengine_submit(desc);
> >> +	dma_async_issue_pending(channel);
> >> +	return 0;
> >> +}
> >> +
> >>
> >> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
> >> +{
> >> +	struct mxs_auart_port *s = param;
> >> +
> >> +	if (!mxs_dma_is_apbx(chan))
> >> +		return false;
> >> +
> >> +	if (s->dma_channel == chan->chan_id) {
> >> +		chan->private =&s->dma_data;
> > dont use chan->private. You need to dmaengine_slave_config API
> please see the drivers/dma/mxs-dma.c:mxs_dam_alloc_chan_resoures().
> 
> The mxs-dma driver uses ->private to store the channel interrupt number.
And which it should not be doing. private is not supposed to be used for
passing info. If it is generic add to slave config.

-- 
Vinod Koul
Intel Corp.

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

? 2012?10?25? 14:07, Vinod Koul ??:
> On Thu, 2012-10-25 at 13:50 +0800, Huang Shijie wrote:
>> ? 2012?10?25? 12:18, Vinod Koul ??:
>>>> +
>>>> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
>>>> +{
>>>> +	struct dma_async_tx_descriptor *desc;
>>>> +	struct scatterlist *sgl =&s->tx_sgl;
>>>> +	struct dma_chan *channel = s->tx_dma_chan;
>>>> +	u32 pio;
>>>> +
>>>> +	/* [1] : send PIO. Note, the first pio word is CTRL1. */
>>>> +	pio = AUART_CTRL1_XFER_COUNT(size);
>>>> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
>>>> +					1, DMA_TRANS_NONE, 0);
>>> this seems like a hack. API expects a scatterlist as argument.
>>> Same thing about direction, NONE doesnt mean anything for dma transfer.
>> It's not a hack. this DMA descriptor is used to set the registers.
>> Please see the code in drivers/dma/mxs-dma.c:mxs_dam_prep_slave_sg().
> yes it is, and also an abuse of the api.
> prep_slave_sg() expects a scatter list and you are passing something
> else and using DMA_TRANS_NONE to do that, which makes no sense!!!
>
> If you have to setup your registers you need to setup based on what APIs
> passed you and not by abusing.
>
yes. I have to setup the register. Could you told me which API is the 
right API?

It seems to the mxs-dma needs a patch again.

>>>> +	if (!desc) {
>>>> +		dev_err(s->dev, "step 1 error\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	/* [2] : set DMA buffer. */
>>>> +	sg_init_one(sgl, s->tx_dma_buf, size);
>>>> +	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
>>>> +	desc = dmaengine_prep_slave_sg(channel, sgl,
>>>> +			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>>>> +	if (!desc) {
>>>> +		dev_err(s->dev, "step 2 error\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	/* [3] : submit the DMA */
>>>> +	desc->callback = dma_tx_callback;
>>>> +	desc->callback_param = s;
>>>> +	dmaengine_submit(desc);
>>>> +	dma_async_issue_pending(channel);
>>>> +	return 0;
>>>> +}
>>>> +
>>>>
>>>> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
>>>> +{
>>>> +	struct mxs_auart_port *s = param;
>>>> +
>>>> +	if (!mxs_dma_is_apbx(chan))
>>>> +		return false;
>>>> +
>>>> +	if (s->dma_channel == chan->chan_id) {
>>>> +		chan->private =&s->dma_data;
>>> dont use chan->private. You need to dmaengine_slave_config API
>> please see the drivers/dma/mxs-dma.c:mxs_dam_alloc_chan_resoures().
>>
>> The mxs-dma driver uses ->private to store the channel interrupt number.
> And which it should not be doing. private is not supposed to be used for
> passing info. If it is generic add to slave config.
>
Could you give me an example which do not use the private?
The imx-sdma also uses the private to pass some info.

thanks
Huang Shijie

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Vinod Koul]

On Thu, 2012-10-25 at 17:15 +0800, Huang Shijie wrote:
> yes. I have to setup the register. Could you told me which API is the 
> right API?
dmaengine_slave_config() should be used to send the slave specfic
parameters
> 
> It seems to the mxs-dma needs a patch again. 
Yes definitely :)

-- 
Vinod Koul
Intel Corp.

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

? 2012?10?25? 19:08, Vinod Koul ??:
> On Thu, 2012-10-25 at 17:15 +0800, Huang Shijie wrote:
>> yes. I have to setup the register. Could you told me which API is the
>> right API?
> dmaengine_slave_config() should be used to send the slave specfic
> parameters
It seems hard to set the registers by the

dmaengine_slave_config().

[1] firstly, there are several drivers use the mxs-dma, the gpmi-nand, mxs-mmc,spi-mxs, i2c-mxs.
        If we set the registers by the dmaengine_slave_config(), we must have the register base address for gpmi, mxs, spi, i2c.
      It's not a good idea to access these registers in the mxs-dma driver.

[2] secondly, take gpmi_read_page() for example, it uses the DMA_TRANS_NONE several times :
     If we set the registers by the dmaengine_slave_config(), the gpmi_read_page() will become like:
     .....................................
     dmaengine_slave_config()
     dmaengine_prep_slave_sg().
     ...................................

     dmaengine_slave_config()
     dmaengine_prep_slave_sg().
     ...................................

      dmaengine_slave_config()
      dmaengine_prep_slave_sg().
     ...................................

     Is it a nice look?

  [3] dma_slave_config{} does not have the fields to contain the registers value.


So I think the  current code it's ok, we'd better do not change it.

thanks
Huang Shijie

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Lauri Hintsala]

Hi Huang,

DMA support doesn't work with latest stable v3.6.5 or development 
3.7-rc5 kernels. I get following error message when I open the serial 
port /dev/ttyAPP0:

[   48.730000] mxs-auart 8006a000.serial: step 1 error
[   48.750000] mxs-auart 8006a000.serial: We can not start up the DMA.


On 10/24/2012 01:27 PM, Huang Shijie wrote:
> Only we meet the following conditions, we can enable the DMA support for
> auart:
>
>    (1) We enable the DMA support in the dts file, such as
>        arch/arm/boot/dts/imx28.dtsi.
>
>    (2) We enable the hardware flow control.

Why HW flow control is required?

We need high speed auart without flow control. I have tested kernel from 
Freescale's BSP and the performance was good without HW flow control.

Best Regards,
Lauri Hintsala


>    (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
>        we can not add the DMA support to mx23.
>
> Signed-off-by: Huang Shijie <b32955@freescale.com>
> ---
>   .../bindings/tty/serial/fsl-mxs-auart.txt          |    8 +
>   drivers/tty/serial/mxs-auart.c                     |  318 +++++++++++++++++++-
>   2 files changed, 321 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> index 2ee903f..273a8d5 100644
> --- a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> +++ b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> @@ -6,11 +6,19 @@ Required properties:
>   - reg : Address and length of the register set for the device
>   - interrupts : Should contain the auart interrupt numbers
>
> +Optional properties:
> +- fsl,auart-dma-channel : The DMA channels, the first is for RX, the other
> +		is for TX. If you add this property, it also means that you
> +		will enable the DMA support for the auart.
> +		Note: due to the hardware bug in imx23(see errata : 2836),
> +		only the imx28 can enable the DMA support for the auart.
> +
>   Example:
>   auart0: serial at 8006a000 {
>   	compatible = "fsl,imx28-auart", "fsl,imx23-auart";
>   	reg = <0x8006a000 0x2000>;
>   	interrupts = <112 70 71>;
> +	fsl,auart-dma-channel = <8 9>;
>   };
>
>   Note: Each auart port should have an alias correctly numbered in "aliases"
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index 06d7271..d593e0a 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -34,6 +34,8 @@
>   #include <linux/io.h>
>   #include <linux/pinctrl/consumer.h>
>   #include <linux/of_device.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/fsl/mxs-dma.h>
>
>   #include <asm/cacheflush.h>
>
> @@ -71,6 +73,15 @@
>
>   #define AUART_CTRL0_SFTRST			(1 << 31)
>   #define AUART_CTRL0_CLKGATE			(1 << 30)
> +#define AUART_CTRL0_RXTO_ENABLE			(1 << 27)
> +#define AUART_CTRL0_RXTIMEOUT(v)		(((v) & 0x7ff) << 16)
> +#define AUART_CTRL0_XFER_COUNT(v)		((v) & 0xffff)
> +
> +#define AUART_CTRL1_XFER_COUNT(v)		((v) & 0xffff)
> +
> +#define AUART_CTRL2_DMAONERR			(1 << 26)
> +#define AUART_CTRL2_TXDMAE			(1 << 25)
> +#define AUART_CTRL2_RXDMAE			(1 << 24)
>
>   #define AUART_CTRL2_CTSEN			(1 << 15)
>   #define AUART_CTRL2_RTSEN			(1 << 14)
> @@ -111,6 +122,7 @@
>   #define AUART_STAT_BERR				(1 << 18)
>   #define AUART_STAT_PERR				(1 << 17)
>   #define AUART_STAT_FERR				(1 << 16)
> +#define AUART_STAT_RXCOUNT_MASK			0xffff
>
>   static struct uart_driver auart_driver;
>
> @@ -122,7 +134,10 @@ enum mxs_auart_type {
>   struct mxs_auart_port {
>   	struct uart_port port;
>
> -	unsigned int flags;
> +#define MXS_AUART_DMA_CONFIG	0x1
> +#define MXS_AUART_DMA_ENABLED	0x2
> +#define MXS_AUART_DMA_TX_SYNC	2  /* bit 2 */
> +	unsigned long flags;
>   	unsigned int ctrl;
>   	enum mxs_auart_type devtype;
>
> @@ -130,6 +145,20 @@ struct mxs_auart_port {
>
>   	struct clk *clk;
>   	struct device *dev;
> +
> +	/* for DMA */
> +	struct mxs_dma_data dma_data;
> +	int dma_channel_rx, dma_channel_tx;
> +	int dma_irq_rx, dma_irq_tx;
> +	int dma_channel;
> +
> +	struct scatterlist tx_sgl;
> +	struct dma_chan	*tx_dma_chan;
> +	void *tx_dma_buf;
> +
> +	struct scatterlist rx_sgl;
> +	struct dma_chan	*rx_dma_chan;
> +	void *rx_dma_buf;
>   };
>
>   static struct platform_device_id mxs_auart_devtype[] = {
> @@ -155,14 +184,107 @@ static inline int is_imx28_auart(struct mxs_auart_port *s)
>   	return s->devtype == IMX28_AUART;
>   }
>
> +static inline bool auart_dma_enabled(struct mxs_auart_port *s)
> +{
> +	return s->flags & MXS_AUART_DMA_ENABLED;
> +}
> +
>   static void mxs_auart_stop_tx(struct uart_port *u);
>
>   #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)
>
> -static inline void mxs_auart_tx_chars(struct mxs_auart_port *s)
> +static void mxs_auart_tx_chars(struct mxs_auart_port *s);
> +
> +static void dma_tx_callback(void *param)
>   {
> +	struct mxs_auart_port *s = param;
>   	struct circ_buf *xmit = &s->port.state->xmit;
>
> +	dma_unmap_sg(s->dev, &s->tx_sgl, 1, DMA_TO_DEVICE);
> +
> +	/* clear the bit used to serialize the DMA tx. */
> +	clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
> +	smp_mb__after_clear_bit();
> +
> +	/* wake up the possible processes. */
> +	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> +		uart_write_wakeup(&s->port);
> +
> +	mxs_auart_tx_chars(s);
> +}
> +
> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
> +{
> +	struct dma_async_tx_descriptor *desc;
> +	struct scatterlist *sgl = &s->tx_sgl;
> +	struct dma_chan *channel = s->tx_dma_chan;
> +	u32 pio;
> +
> +	/* [1] : send PIO. Note, the first pio word is CTRL1. */
> +	pio = AUART_CTRL1_XFER_COUNT(size);
> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio,
> +					1, DMA_TRANS_NONE, 0);
> +	if (!desc) {
> +		dev_err(s->dev, "step 1 error\n");
> +		return -EINVAL;
> +	}
> +
> +	/* [2] : set DMA buffer. */
> +	sg_init_one(sgl, s->tx_dma_buf, size);
> +	dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
> +	desc = dmaengine_prep_slave_sg(channel, sgl,
> +			1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +	if (!desc) {
> +		dev_err(s->dev, "step 2 error\n");
> +		return -EINVAL;
> +	}
> +
> +	/* [3] : submit the DMA */
> +	desc->callback = dma_tx_callback;
> +	desc->callback_param = s;
> +	dmaengine_submit(desc);
> +	dma_async_issue_pending(channel);
> +	return 0;
> +}
> +
> +static void mxs_auart_tx_chars(struct mxs_auart_port *s)
> +{
> +	struct circ_buf *xmit = &s->port.state->xmit;
> +
> +	if (auart_dma_enabled(s)) {
> +		int i = 0;
> +		int size;
> +		void *buffer = s->tx_dma_buf;
> +
> +		if (test_and_set_bit(MXS_AUART_DMA_TX_SYNC, &s->flags))
> +			return;
> +
> +		while (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
> +			size = min_t(u32, UART_XMIT_SIZE - i,
> +				     CIRC_CNT_TO_END(xmit->head,
> +						     xmit->tail,
> +						     UART_XMIT_SIZE));
> +			memcpy(buffer + i, xmit->buf + xmit->tail, size);
> +			xmit->tail = (xmit->tail + size) & (UART_XMIT_SIZE - 1);
> +
> +			i += size;
> +			if (i >= UART_XMIT_SIZE)
> +				break;
> +		}
> +
> +		if (uart_tx_stopped(&s->port))
> +			mxs_auart_stop_tx(&s->port);
> +
> +		if (i) {
> +			mxs_auart_dma_tx(s, i);
> +		} else {
> +			clear_bit(MXS_AUART_DMA_TX_SYNC, &s->flags);
> +			smp_mb__after_clear_bit();
> +		}
> +		return;
> +	}
> +
> +
>   	while (!(readl(s->port.membase + AUART_STAT) &
>   		 AUART_STAT_TXFF)) {
>   		if (s->port.x_char) {
> @@ -316,10 +438,155 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
>   	return mctrl;
>   }
>
> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
> +{
> +	struct mxs_auart_port *s = param;
> +
> +	if (!mxs_dma_is_apbx(chan))
> +		return false;
> +
> +	if (s->dma_channel == chan->chan_id) {
> +		chan->private = &s->dma_data;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
> +static void dma_rx_callback(void *arg)
> +{
> +	struct mxs_auart_port *s = (struct mxs_auart_port *) arg;
> +	struct tty_struct *tty = s->port.state->port.tty;
> +	int count;
> +	u32 stat;
> +
> +	stat = readl(s->port.membase + AUART_STAT);
> +	stat &= ~(AUART_STAT_OERR | AUART_STAT_BERR |
> +			AUART_STAT_PERR | AUART_STAT_FERR);
> +
> +	count = stat & AUART_STAT_RXCOUNT_MASK;
> +	tty_insert_flip_string(tty, s->rx_dma_buf, count);
> +
> +	writel(stat, s->port.membase + AUART_STAT);
> +	tty_flip_buffer_push(tty);
> +
> +	/* start the next DMA for RX. */
> +	mxs_auart_dma_prep_rx(s);
> +}
> +
> +static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s)
> +{
> +	struct dma_async_tx_descriptor *desc;
> +	struct scatterlist *sgl = &s->rx_sgl;
> +	struct dma_chan *channel = s->rx_dma_chan;
> +	u32 pio[1];
> +
> +	/* [1] : send PIO */
> +	pio[0] = AUART_CTRL0_RXTO_ENABLE
> +		| AUART_CTRL0_RXTIMEOUT(0x80)
> +		| AUART_CTRL0_XFER_COUNT(UART_XMIT_SIZE);
> +	desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
> +					1, DMA_TRANS_NONE, 0);
> +	if (!desc) {
> +		dev_err(s->dev, "step 1 error\n");
> +		return -EINVAL;
> +	}
> +
> +	/* [2] : send DMA request */
> +	sg_init_one(sgl, s->rx_dma_buf, UART_XMIT_SIZE);
> +	dma_map_sg(s->dev, sgl, 1, DMA_FROM_DEVICE);
> +	desc = dmaengine_prep_slave_sg(channel, sgl, 1, DMA_DEV_TO_MEM,
> +					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +	if (!desc) {
> +		dev_err(s->dev, "step 2 error\n");
> +		return -1;
> +	}
> +
> +	/* [3] : submit the DMA, but do not issue it. */
> +	desc->callback = dma_rx_callback;
> +	desc->callback_param = s;
> +	dmaengine_submit(desc);
> +	dma_async_issue_pending(channel);
> +	return 0;
> +}
> +
> +static void mxs_auart_dma_exit_channel(struct mxs_auart_port *s)
> +{
> +	if (s->tx_dma_chan) {
> +		dma_release_channel(s->tx_dma_chan);
> +		s->tx_dma_chan = NULL;
> +	}
> +	if (s->rx_dma_chan) {
> +		dma_release_channel(s->rx_dma_chan);
> +		s->rx_dma_chan = NULL;
> +	}
> +
> +	kfree(s->tx_dma_buf);
> +	kfree(s->rx_dma_buf);
> +	s->tx_dma_buf = NULL;
> +	s->rx_dma_buf = NULL;
> +}
> +
> +static void mxs_auart_dma_exit(struct mxs_auart_port *s)
> +{
> +
> +	writel(AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE | AUART_CTRL2_DMAONERR,
> +		s->port.membase + AUART_CTRL2_CLR);
> +
> +	mxs_auart_dma_exit_channel(s);
> +	s->flags &= ~MXS_AUART_DMA_ENABLED;
> +}
> +
> +static int mxs_auart_dma_init(struct mxs_auart_port *s)
> +{
> +	dma_cap_mask_t mask;
> +
> +	if (auart_dma_enabled(s))
> +		return 0;
> +
> +	/* We do not get the right DMA channels. */
> +	if (s->dma_channel_rx == -1 || s->dma_channel_rx == -1)
> +		return -EINVAL;
> +
> +	/* init for RX */
> +	dma_cap_zero(mask);
> +	dma_cap_set(DMA_SLAVE, mask);
> +	s->dma_channel = s->dma_channel_rx;
> +	s->dma_data.chan_irq = s->dma_irq_rx;
> +	s->rx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
> +	if (!s->rx_dma_chan)
> +		goto err_out;
> +	s->rx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
> +	if (!s->rx_dma_buf)
> +		goto err_out;
> +
> +	/* init for TX */
> +	s->dma_channel = s->dma_channel_tx;
> +	s->dma_data.chan_irq = s->dma_irq_tx;
> +	s->tx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
> +	if (!s->tx_dma_chan)
> +		goto err_out;
> +	s->tx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
> +	if (!s->tx_dma_buf)
> +		goto err_out;
> +
> +	/* set the flags */
> +	s->flags |= MXS_AUART_DMA_ENABLED;
> +	dev_dbg(s->dev, "enabled the DMA support.");
> +
> +	return 0;
> +
> +err_out:
> +	mxs_auart_dma_exit_channel(s);
> +	return -EINVAL;
> +
> +}
> +
>   static void mxs_auart_settermios(struct uart_port *u,
>   				 struct ktermios *termios,
>   				 struct ktermios *old)
>   {
> +	struct mxs_auart_port *s = to_auart_port(u);
>   	u32 bm, ctrl, ctrl2, div;
>   	unsigned int cflag, baud;
>
> @@ -391,10 +658,23 @@ static void mxs_auart_settermios(struct uart_port *u,
>   		ctrl |= AUART_LINECTRL_STP2;
>
>   	/* figure out the hardware flow control settings */
> -	if (cflag & CRTSCTS)
> +	if (cflag & CRTSCTS) {
> +		/*
> +		 * The DMA has a bug(see errata:2836) in mx23.
> +		 * So we can not implement the DMA for auart in mx23,
> +		 * we can only implement the DMA support for auart
> +		 * in mx28.
> +		 */
> +		if (is_imx28_auart(s) && (s->flags & MXS_AUART_DMA_CONFIG)) {
> +			if (!mxs_auart_dma_init(s))
> +				/* enable DMA tranfer */
> +				ctrl2 |= AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE
> +				       | AUART_CTRL2_DMAONERR;
> +		}
>   		ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
> -	else
> +	} else {
>   		ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
> +	}
>
>   	/* set baud rate */
>   	baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);
> @@ -406,6 +686,17 @@ static void mxs_auart_settermios(struct uart_port *u,
>   	writel(ctrl2, u->membase + AUART_CTRL2);
>
>   	uart_update_timeout(u, termios->c_cflag, baud);
> +
> +	/* prepare for the DMA RX. */
> +	if (auart_dma_enabled(s)) {
> +		if (!mxs_auart_dma_prep_rx(s)) {
> +			/* Disable the normal RX interrupt. */
> +			writel(AUART_INTR_RXIEN, u->membase + AUART_INTR_CLR);
> +		} else {
> +			mxs_auart_dma_exit(s);
> +			dev_err(s->dev, "We can not start up the DMA.\n");
> +		}
> +	}
>   }
>
>   static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
> @@ -484,6 +775,9 @@ static void mxs_auart_shutdown(struct uart_port *u)
>   {
>   	struct mxs_auart_port *s = to_auart_port(u);
>
> +	if (auart_dma_enabled(s))
> +		mxs_auart_dma_exit(s);
> +
>   	writel(AUART_CTRL2_UARTEN, u->membase + AUART_CTRL2_CLR);
>
>   	writel(AUART_INTR_RXIEN | AUART_INTR_RTIEN | AUART_INTR_CTSMIEN,
> @@ -717,6 +1011,7 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
>   		struct platform_device *pdev)
>   {
>   	struct device_node *np = pdev->dev.of_node;
> +	u32 dma_channel[2];
>   	int ret;
>
>   	if (!np)
> @@ -730,6 +1025,20 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
>   	}
>   	s->port.line = ret;
>
> +	s->dma_irq_rx = platform_get_irq(pdev, 1);
> +	s->dma_irq_tx = platform_get_irq(pdev, 2);
> +
> +	ret = of_property_read_u32_array(np, "fsl,auart-dma-channel",
> +					dma_channel, 2);
> +	if (ret == 0) {
> +		s->dma_channel_rx = dma_channel[0];
> +		s->dma_channel_tx = dma_channel[1];
> +
> +		s->flags |= MXS_AUART_DMA_CONFIG;
> +	} else {
> +		s->dma_channel_rx = -1;
> +		s->dma_channel_tx = -1;
> +	}
>   	return 0;
>   }
>
> @@ -787,7 +1096,6 @@ static int __devinit mxs_auart_probe(struct platform_device *pdev)
>   	s->port.type = PORT_IMX;
>   	s->port.dev = s->dev = get_device(&pdev->dev);
>
> -	s->flags = 0;
>   	s->ctrl = 0;
>
>   	s->irq = platform_get_irq(pdev, 0);
>

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

? 2012?11?13? 17:42, Lauri Hintsala ??:
> Hi Huang,
>
> DMA support doesn't work with latest stable v3.6.5 or development 
> 3.7-rc5 kernels. I get following error message when I open the serial 
> port /dev/ttyAPP0:
>
> [ 48.730000] mxs-auart 8006a000.serial: step 1 error
> [ 48.750000] mxs-auart 8006a000.serial: We can not start up the DMA.
>
I tested this patch set in imx28-evk board Rev C with linux-next-20121114.
it works fine.

Maybe you can try the linux-next code.

About the flow control:
If we do not enable the HW flow control, the data may lost. And I do not 
know how to handle with the Xon/Xoff when the DMA is supported.

Best Regards
Huang Shijie

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Lauri Hintsala]

Hi,

On 11/15/2012 05:20 AM, Huang Shijie wrote:
> ? 2012?11?13? 17:42, Lauri Hintsala ??:
>> Hi Huang,
>>
>> DMA support doesn't work with latest stable v3.6.5 or development
>> 3.7-rc5 kernels. I get following error message when I open the serial
>> port /dev/ttyAPP0:
>>
>> [ 48.730000] mxs-auart 8006a000.serial: step 1 error
>> [ 48.750000] mxs-auart 8006a000.serial: We can not start up the DMA.
>>
> I tested this patch set in imx28-evk board Rev C with linux-next-20121114.
> it works fine.
>
> Maybe you can try the linux-next code.

I tested linux-next-20121114 on apx4devkit (imx28 based device) and I 
got the same error message:

# stty -F /dev/ttyAPP0 crtscts; microcom /dev/ttyAPP0 -s 115200
[  133.710000] mxs-auart 8006a000.serial: step 1 error
[  133.720000] mxs-auart 8006a000.serial: We can not start up the DMA.


> About the flow control:
> If we do not enable the HW flow control, the data may lost. And I do not
> know how to handle with the Xon/Xoff when the DMA is supported.

I do not have the answer but it is already implemented in Freescale's 
reference kernel 
(http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/serial/mxs-auart.c?h=imx_2.6.35_11.09.01). 
So I think it is possible to handle all data without HW flow control.


Best Regards,
Lauri Hintsala

[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Huang Shijie]

? 2012?11?15? 15:22, Lauri Hintsala ??:
> Hi,
>
> On 11/15/2012 05:20 AM, Huang Shijie wrote:
>> ? 2012?11?13? 17:42, Lauri Hintsala ??:
>>> Hi Huang,
>>>
>>> DMA support doesn't work with latest stable v3.6.5 or development
>>> 3.7-rc5 kernels. I get following error message when I open the serial
>>> port /dev/ttyAPP0:
>>>
>>> [ 48.730000] mxs-auart 8006a000.serial: step 1 error
>>> [ 48.750000] mxs-auart 8006a000.serial: We can not start up the DMA.
>>>
>> I tested this patch set in imx28-evk board Rev C with 
>> linux-next-20121114.
>> it works fine.
>>
>> Maybe you can try the linux-next code.
>
> I tested linux-next-20121114 on apx4devkit (imx28 based device) and I 
> got the same error message:
>
> # stty -F /dev/ttyAPP0 crtscts; microcom /dev/ttyAPP0 -s 115200
> [  133.710000] mxs-auart 8006a000.serial: step 1 error
> [  133.720000] mxs-auart 8006a000.serial: We can not start up the DMA.
Could you test this patch?

thanks
Huang  Shijie
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[PATCH v2 2/3] serial: mxs-auart: add the DMA support for mx28

[Lauri Hintsala]

Hi,

On 11/15/2012 11:11 AM, Huang Shijie wrote:
>> I tested linux-next-20121114 on apx4devkit (imx28 based device) and I
>> got the same error message:
>>
>> # stty -F /dev/ttyAPP0 crtscts; microcom /dev/ttyAPP0 -s 115200
>> [  133.710000] mxs-auart 8006a000.serial: step 1 error
>> [  133.720000] mxs-auart 8006a000.serial: We can not start up the DMA.
> Could you test this patch?

I don't get error messages with your latest patch but the CPU freezes 
after it has received first byte. Freezing happens only if flow control 
(and of course DMA) is enabled. Sending data doesn't freeze the CPU. Are 
you able to send data without freezing?

I used busybox's microcom to transfer data.

Lauri

[PATCH v2 3/3] ARM: dts: enable dma support for auart0 in mx28

[Huang Shijie]

enable the dma support for auart0 in mx28.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 arch/arm/boot/dts/imx28.dtsi |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
index e16d631..73d1a9f 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -798,6 +798,7 @@
 				compatible = "fsl,imx28-auart", "fsl,imx23-auart";
 				reg = <0x8006a000 0x2000>;
 				interrupts = <112 70 71>;
+				fsl,auart-dma-channel = <8 9>;
 				clocks = <&clks 45>;
 				status = "disabled";
 			};
-- 
1.7.0.4