[PATCH v4 2/6] serial: imx: add DMA support for imx6q
Huang Shijie
b32955 at freescale.com
Mon Jul 8 05:14:18 EDT 2013
We only enable the DMA support when the following are meet:
[1] The uart port supports the hardware flow control(CTS/RTS).
(Some uart port does not support the CTS/RTS.)
[2] The application enables the CTS/RTS.
[3] The Soc is imx6q.
For the sdma's firmware limit, we do not support the DMA except
the imx6q platform.
[4] The uart is not used as a console.
Signed-off-by: Huang Shijie <b32955 at freescale.com>
---
drivers/tty/serial/imx.c | 405 +++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 400 insertions(+), 5 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index a9643ef..d04a09e 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -49,9 +49,11 @@
#include <linux/of_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/io.h>
+#include <linux/dma-mapping.h>
#include <asm/irq.h>
#include <linux/platform_data/serial-imx.h>
+#include <linux/platform_data/dma-imx.h>
/* Register definitions */
#define URXD0 0x0 /* Receiver Register */
@@ -83,6 +85,7 @@
#define UCR1_ADBR (1<<14) /* Auto detect baud rate */
#define UCR1_TRDYEN (1<<13) /* Transmitter ready interrupt enable */
#define UCR1_IDEN (1<<12) /* Idle condition interrupt */
+#define UCR1_ICD_REG(x) (((x) & 3) << 10) /* idle condition detect */
#define UCR1_RRDYEN (1<<9) /* Recv ready interrupt enable */
#define UCR1_RDMAEN (1<<8) /* Recv ready DMA enable */
#define UCR1_IREN (1<<7) /* Infrared interface enable */
@@ -91,6 +94,7 @@
#define UCR1_SNDBRK (1<<4) /* Send break */
#define UCR1_TDMAEN (1<<3) /* Transmitter ready DMA enable */
#define IMX1_UCR1_UARTCLKEN (1<<2) /* UART clock enabled, i.mx1 only */
+#define UCR1_ATDMAEN (1<<2) /* Aging DMA Timer Enable */
#define UCR1_DOZE (1<<1) /* Doze */
#define UCR1_UARTEN (1<<0) /* UART enabled */
#define UCR2_ESCI (1<<15) /* Escape seq interrupt enable */
@@ -126,6 +130,7 @@
#define UCR4_ENIRI (1<<8) /* Serial infrared interrupt enable */
#define UCR4_WKEN (1<<7) /* Wake interrupt enable */
#define UCR4_REF16 (1<<6) /* Ref freq 16 MHz */
+#define UCR4_IDDMAEN (1<<6) /* DMA IDLE Condition Detected */
#define UCR4_IRSC (1<<5) /* IR special case */
#define UCR4_TCEN (1<<3) /* Transmit complete interrupt enable */
#define UCR4_BKEN (1<<2) /* Break condition interrupt enable */
@@ -210,6 +215,19 @@ struct imx_port {
struct clk *clk_ipg;
struct clk *clk_per;
const struct imx_uart_data *devdata;
+
+ /* DMA fields */
+ unsigned int dma_is_inited:1;
+ unsigned int dma_is_enabled:1;
+ unsigned int dma_is_rxing:1;
+ unsigned int dma_is_txing:1;
+ struct dma_chan *dma_chan_rx, *dma_chan_tx;
+ struct scatterlist rx_sgl, tx_sgl[2];
+ void *rx_buf;
+ unsigned int rx_bytes, tx_bytes;
+ struct work_struct tsk_dma_rx, tsk_dma_tx;
+ unsigned int dma_tx_nents;
+ wait_queue_head_t dma_wait;
};
struct imx_port_ucrs {
@@ -400,6 +418,13 @@ static void imx_stop_tx(struct uart_port *port)
return;
}
+ /*
+ * We are maybe in the SMP context, so if the DMA TX thread is running
+ * on other cpu, we have to wait for it to finish.
+ */
+ if (sport->dma_is_enabled && sport->dma_is_txing)
+ return;
+
temp = readl(sport->port.membase + UCR1);
writel(temp & ~UCR1_TXMPTYEN, sport->port.membase + UCR1);
}
@@ -412,6 +437,13 @@ static void imx_stop_rx(struct uart_port *port)
struct imx_port *sport = (struct imx_port *)port;
unsigned long temp;
+ /*
+ * We are maybe in the SMP context, so if the DMA TX thread is running
+ * on other cpu, we have to wait for it to finish.
+ */
+ if (sport->dma_is_enabled && sport->dma_is_rxing)
+ return;
+
temp = readl(sport->port.membase + UCR2);
writel(temp & ~UCR2_RXEN, sport->port.membase + UCR2);
}
@@ -447,6 +479,95 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
imx_stop_tx(&sport->port);
}
+static void dma_tx_callback(void *data)
+{
+ struct imx_port *sport = data;
+ struct scatterlist *sgl = &sport->tx_sgl[0];
+ struct circ_buf *xmit = &sport->port.state->xmit;
+ unsigned long flags;
+
+ dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+
+ sport->dma_is_txing = 0;
+
+ /* update the stat */
+ spin_lock_irqsave(&sport->port.lock, flags);
+ xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
+ sport->port.icount.tx += sport->tx_bytes;
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+
+ dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(&sport->port);
+
+ if (waitqueue_active(&sport->dma_wait)) {
+ wake_up(&sport->dma_wait);
+ dev_dbg(sport->port.dev, "exit in %s.\n", __func__);
+ return;
+ }
+
+ schedule_work(&sport->tsk_dma_tx);
+}
+
+static void dma_tx_work(struct work_struct *w)
+{
+ struct imx_port *sport = container_of(w, struct imx_port, tsk_dma_tx);
+ struct circ_buf *xmit = &sport->port.state->xmit;
+ struct scatterlist *sgl = sport->tx_sgl;
+ struct dma_async_tx_descriptor *desc;
+ struct dma_chan *chan = sport->dma_chan_tx;
+ struct device *dev = sport->port.dev;
+ enum dma_status status;
+ unsigned long flags;
+ int ret;
+
+ status = chan->device->device_tx_status(chan, (dma_cookie_t)0, NULL);
+ if (DMA_IN_PROGRESS == status)
+ return;
+
+ spin_lock_irqsave(&sport->port.lock, flags);
+ sport->tx_bytes = uart_circ_chars_pending(xmit);
+ if (sport->tx_bytes == 0) {
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+ return;
+ }
+
+ if (xmit->tail > xmit->head) {
+ sport->dma_tx_nents = 2;
+ sg_init_table(sgl, 2);
+ sg_set_buf(sgl, xmit->buf + xmit->tail,
+ UART_XMIT_SIZE - xmit->tail);
+ sg_set_buf(sgl + 1, xmit->buf, xmit->head);
+ } else {
+ sport->dma_tx_nents = 1;
+ sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
+ }
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+
+ ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+ if (ret == 0) {
+ dev_err(dev, "DMA mapping error for TX.\n");
+ return;
+ }
+ desc = dmaengine_prep_slave_sg(chan, sgl, sport->dma_tx_nents,
+ DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
+ if (!desc) {
+ dev_err(dev, "We cannot prepare for the TX slave dma!\n");
+ return;
+ }
+ desc->callback = dma_tx_callback;
+ desc->callback_param = sport;
+
+ dev_dbg(dev, "TX: prepare to send %lu bytes by DMA.\n",
+ uart_circ_chars_pending(xmit));
+ /* fire it */
+ sport->dma_is_txing = 1;
+ dmaengine_submit(desc);
+ dma_async_issue_pending(chan);
+ return;
+}
+
/*
* interrupts disabled on entry
*/
@@ -473,8 +594,10 @@ static void imx_start_tx(struct uart_port *port)
temp |= UCR4_OREN;
writel(temp, sport->port.membase + UCR4);
- temp = readl(sport->port.membase + UCR1);
- writel(temp | UCR1_TXMPTYEN, sport->port.membase + UCR1);
+ if (!sport->dma_is_enabled) {
+ temp = readl(sport->port.membase + UCR1);
+ writel(temp | UCR1_TXMPTYEN, sport->port.membase + UCR1);
+ }
if (USE_IRDA(sport)) {
temp = readl(sport->port.membase + UCR1);
@@ -486,6 +609,15 @@ static void imx_start_tx(struct uart_port *port)
writel(temp, sport->port.membase + UCR4);
}
+ if (sport->dma_is_enabled) {
+ /*
+ * We may in the interrupt context, so arise a work_struct to
+ * do the real job.
+ */
+ schedule_work(&sport->tsk_dma_tx);
+ return;
+ }
+
if (readl(sport->port.membase + uts_reg(sport)) & UTS_TXEMPTY)
imx_transmit_buffer(sport);
}
@@ -601,6 +733,28 @@ out:
return IRQ_HANDLED;
}
+/*
+ * If the RXFIFO is filled with some data, and then we
+ * arise a DMA operation to receive them.
+ */
+static void imx_dma_rxint(struct imx_port *sport)
+{
+ unsigned long temp;
+
+ temp = readl(sport->port.membase + USR2);
+ if ((temp & USR2_RDR) && !sport->dma_is_rxing) {
+ sport->dma_is_rxing = 1;
+
+ /* disable the `Recerver Ready Interrrupt` */
+ temp = readl(sport->port.membase + UCR1);
+ temp &= ~(UCR1_RRDYEN);
+ writel(temp, sport->port.membase + UCR1);
+
+ /* tell the DMA to receive the data. */
+ schedule_work(&sport->tsk_dma_rx);
+ }
+}
+
static irqreturn_t imx_int(int irq, void *dev_id)
{
struct imx_port *sport = dev_id;
@@ -609,8 +763,12 @@ static irqreturn_t imx_int(int irq, void *dev_id)
sts = readl(sport->port.membase + USR1);
- if (sts & USR1_RRDY)
- imx_rxint(irq, dev_id);
+ if (sts & USR1_RRDY) {
+ if (sport->dma_is_enabled)
+ imx_dma_rxint(sport);
+ else
+ imx_rxint(irq, dev_id);
+ }
if (sts & USR1_TRDY &&
readl(sport->port.membase + UCR1) & UCR1_TXMPTYEN)
@@ -667,7 +825,8 @@ static void imx_set_mctrl(struct uart_port *port, unsigned int mctrl)
temp = readl(sport->port.membase + UCR2) & ~UCR2_CTS;
if (mctrl & TIOCM_RTS)
- temp |= UCR2_CTS;
+ if (!sport->dma_is_enabled)
+ temp |= UCR2_CTS;
writel(temp, sport->port.membase + UCR2);
}
@@ -706,6 +865,226 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
return 0;
}
+#define RX_BUF_SIZE (PAGE_SIZE)
+static int start_rx_dma(struct imx_port *sport);
+static void dma_rx_work(struct work_struct *w)
+{
+ struct imx_port *sport = container_of(w, struct imx_port, tsk_dma_rx);
+ struct tty_port *port = &sport->port.state->port;
+
+ if (sport->rx_bytes) {
+ tty_insert_flip_string(port, sport->rx_buf, sport->rx_bytes);
+ tty_flip_buffer_push(port);
+ sport->rx_bytes = 0;
+ }
+
+ if (sport->dma_is_rxing)
+ start_rx_dma(sport);
+}
+
+static void imx_rx_dma_done(struct imx_port *sport)
+{
+ unsigned long temp;
+
+ /* Enable this interrupt when the RXFIFO is empty. */
+ temp = readl(sport->port.membase + UCR1);
+ temp |= UCR1_RRDYEN;
+ writel(temp, sport->port.membase + UCR1);
+
+ sport->dma_is_rxing = 0;
+
+ /* Is the shutdown waiting for us? */
+ if (waitqueue_active(&sport->dma_wait))
+ wake_up(&sport->dma_wait);
+}
+
+/*
+ * There are three kinds of RX DMA interrupts(such as in the MX6Q):
+ * [1] the RX DMA buffer is full.
+ * [2] the Aging timer expires(wait for 8 bytes long)
+ * [3] the Idle Condition Detect(enabled the UCR4_IDDMAEN).
+ *
+ * The [2] is trigger when a character was been sitting in the FIFO
+ * meanwhile [3] can wait for 32 bytes long when the RX line is
+ * on IDLE state and RxFIFO is empty.
+ */
+static void dma_rx_callback(void *data)
+{
+ struct imx_port *sport = data;
+ struct dma_chan *chan = sport->dma_chan_rx;
+ struct scatterlist *sgl = &sport->rx_sgl;
+ struct dma_tx_state state;
+ enum dma_status status;
+ unsigned int count;
+
+ /* unmap it first */
+ dma_unmap_sg(sport->port.dev, sgl, 1, DMA_FROM_DEVICE);
+
+ status = chan->device->device_tx_status(chan, (dma_cookie_t)0, &state);
+ count = RX_BUF_SIZE - state.residue;
+ dev_dbg(sport->port.dev, "We get %d bytes.\n", count);
+
+ if (count) {
+ sport->rx_bytes = count;
+ schedule_work(&sport->tsk_dma_rx);
+ } else
+ imx_rx_dma_done(sport);
+}
+
+static int start_rx_dma(struct imx_port *sport)
+{
+ struct scatterlist *sgl = &sport->rx_sgl;
+ struct dma_chan *chan = sport->dma_chan_rx;
+ struct device *dev = sport->port.dev;
+ struct dma_async_tx_descriptor *desc;
+ int ret;
+
+ sg_init_one(sgl, sport->rx_buf, RX_BUF_SIZE);
+ ret = dma_map_sg(dev, sgl, 1, DMA_FROM_DEVICE);
+ if (ret == 0) {
+ dev_err(dev, "DMA mapping error for RX.\n");
+ return -EINVAL;
+ }
+ desc = dmaengine_prep_slave_sg(chan, sgl, 1, DMA_DEV_TO_MEM,
+ DMA_PREP_INTERRUPT);
+ if (!desc) {
+ dev_err(dev, "We cannot prepare for the RX slave dma!\n");
+ return -EINVAL;
+ }
+ desc->callback = dma_rx_callback;
+ desc->callback_param = sport;
+
+ dev_dbg(dev, "RX: prepare for the DMA.\n");
+ dmaengine_submit(desc);
+ dma_async_issue_pending(chan);
+ return 0;
+}
+
+static void imx_uart_dma_exit(struct imx_port *sport)
+{
+ if (sport->dma_chan_rx) {
+ dma_release_channel(sport->dma_chan_rx);
+ sport->dma_chan_rx = NULL;
+
+ kfree(sport->rx_buf);
+ sport->rx_buf = NULL;
+ }
+
+ if (sport->dma_chan_tx) {
+ dma_release_channel(sport->dma_chan_tx);
+ sport->dma_chan_tx = NULL;
+ }
+
+ sport->dma_is_inited = 0;
+}
+
+static int imx_uart_dma_init(struct imx_port *sport)
+{
+ struct dma_slave_config slave_config;
+ struct device *dev = sport->port.dev;
+ int ret;
+
+ /* Prepare for RX : */
+ sport->dma_chan_rx = dma_request_slave_channel(dev, "rx");
+ if (!sport->dma_chan_rx) {
+ dev_dbg(dev, "cannot get the DMA channel.\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_DEV_TO_MEM;
+ slave_config.src_addr = sport->port.mapbase + URXD0;
+ slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.src_maxburst = RXTL;
+ ret = dmaengine_slave_config(sport->dma_chan_rx, &slave_config);
+ if (ret) {
+ dev_err(dev, "error in RX dma configuration.\n");
+ goto err;
+ }
+
+ sport->rx_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!sport->rx_buf) {
+ dev_err(dev, "cannot alloc DMA buffer.\n");
+ ret = -ENOMEM;
+ goto err;
+ }
+ sport->rx_bytes = 0;
+
+ /* Prepare for TX : */
+ sport->dma_chan_tx = dma_request_slave_channel(dev, "tx");
+ if (!sport->dma_chan_tx) {
+ dev_err(dev, "cannot get the TX DMA channel!\n");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ slave_config.dst_addr = sport->port.mapbase + URTX0;
+ slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.dst_maxburst = TXTL;
+ ret = dmaengine_slave_config(sport->dma_chan_tx, &slave_config);
+ if (ret) {
+ dev_err(dev, "error in TX dma configuration.");
+ goto err;
+ }
+
+ sport->dma_is_inited = 1;
+
+ return 0;
+err:
+ imx_uart_dma_exit(sport);
+ return ret;
+}
+
+static void imx_enable_dma(struct imx_port *sport)
+{
+ unsigned long temp;
+ struct tty_port *port = &sport->port.state->port;
+
+ port->low_latency = 1;
+ INIT_WORK(&sport->tsk_dma_tx, dma_tx_work);
+ INIT_WORK(&sport->tsk_dma_rx, dma_rx_work);
+ init_waitqueue_head(&sport->dma_wait);
+
+ /* set UCR1 */
+ temp = readl(sport->port.membase + UCR1);
+ temp |= UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN |
+ /* wait for 32 idle frames for IDDMA interrupt */
+ UCR1_ICD_REG(3);
+ writel(temp, sport->port.membase + UCR1);
+
+ /* set UCR4 */
+ temp = readl(sport->port.membase + UCR4);
+ temp |= UCR4_IDDMAEN;
+ writel(temp, sport->port.membase + UCR4);
+
+ sport->dma_is_enabled = 1;
+}
+
+static void imx_disable_dma(struct imx_port *sport)
+{
+ unsigned long temp;
+ struct tty_port *port = &sport->port.state->port;
+
+ /* clear UCR1 */
+ temp = readl(sport->port.membase + UCR1);
+ temp &= ~(UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN);
+ writel(temp, sport->port.membase + UCR1);
+
+ /* clear UCR2 */
+ temp = readl(sport->port.membase + UCR2);
+ temp &= ~(UCR2_CTSC | UCR2_CTS);
+ writel(temp, sport->port.membase + UCR2);
+
+ /* clear UCR4 */
+ temp = readl(sport->port.membase + UCR4);
+ temp &= ~UCR4_IDDMAEN;
+ writel(temp, sport->port.membase + UCR4);
+
+ sport->dma_is_enabled = 0;
+ port->low_latency = 0;
+}
+
/* half the RX buffer size */
#define CTSTL 16
@@ -870,6 +1249,15 @@ static void imx_shutdown(struct uart_port *port)
unsigned long temp;
unsigned long flags;
+ if (sport->dma_is_enabled) {
+ /* We have to wait for the DMA to finish. */
+ wait_event(sport->dma_wait,
+ !sport->dma_is_rxing && !sport->dma_is_txing);
+ imx_stop_rx(port);
+ imx_disable_dma(sport);
+ imx_uart_dma_exit(sport);
+ }
+
spin_lock_irqsave(&sport->port.lock, flags);
temp = readl(sport->port.membase + UCR2);
temp &= ~(UCR2_TXEN);
@@ -956,6 +1344,11 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
if (sport->have_rtscts) {
ucr2 &= ~UCR2_IRTS;
ucr2 |= UCR2_CTSC;
+
+ /* Can we enable the DMA support? */
+ if (is_imx6q_uart(sport) && !uart_console(port)
+ && !sport->dma_is_inited)
+ imx_uart_dma_init(sport);
} else {
termios->c_cflag &= ~CRTSCTS;
}
@@ -1069,6 +1462,8 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
if (UART_ENABLE_MS(&sport->port, termios->c_cflag))
imx_enable_ms(&sport->port);
+ if (sport->dma_is_inited && !sport->dma_is_enabled)
+ imx_enable_dma(sport);
spin_unlock_irqrestore(&sport->port.lock, flags);
}
--
1.7.1
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