[PATCH v2 7/9] tty: serial: fsl-lpuart: Use scatter/gather DMA for Tx
Bhuvanchandra DV
bhuvanchandra.dv at toradex.com
Mon Jun 27 22:32:33 PDT 2016
Drop PIO to DMA switching and use scatter/gather DMA for Tx path to improve
performance.
Some part of the code is borrowed from imx serial driver.
Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv at toradex.com>
---
drivers/tty/serial/fsl_lpuart.c | 257 ++++++++++++++++++----------------------
1 file changed, 113 insertions(+), 144 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 51d2b5a..27687d5 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -244,18 +244,18 @@ struct lpuart_port {
struct dma_chan *dma_rx_chan;
struct dma_async_tx_descriptor *dma_tx_desc;
struct dma_async_tx_descriptor *dma_rx_desc;
- dma_addr_t dma_tx_buf_bus;
dma_cookie_t dma_tx_cookie;
dma_cookie_t dma_rx_cookie;
- unsigned char *dma_tx_buf_virt;
unsigned int dma_tx_bytes;
unsigned int dma_rx_bytes;
- int dma_tx_in_progress;
+ bool dma_tx_in_progress;
unsigned int dma_rx_timeout;
struct timer_list lpuart_timer;
- struct scatterlist rx_sgl;
+ struct scatterlist rx_sgl, tx_sgl[2];
struct circ_buf rx_ring;
int rx_dma_rng_buf_len;
+ unsigned int dma_tx_nents;
+ wait_queue_head_t dma_wait;
};
static const struct of_device_id lpuart_dt_ids[] = {
@@ -316,103 +316,118 @@ static void lpuart32_stop_rx(struct uart_port *port)
lpuart32_write(temp & ~UARTCTRL_RE, port->membase + UARTCTRL);
}
-static void lpuart_pio_tx(struct lpuart_port *sport)
+static void lpuart_dma_tx(struct lpuart_port *sport)
{
struct circ_buf *xmit = &sport->port.state->xmit;
- unsigned long flags;
-
- spin_lock_irqsave(&sport->port.lock, flags);
+ struct scatterlist *sgl = sport->tx_sgl;
+ struct device *dev = sport->port.dev;
+ int ret;
- while (!uart_circ_empty(xmit) &&
- readb(sport->port.membase + UARTTCFIFO) < sport->txfifo_size) {
- writeb(xmit->buf[xmit->tail], sport->port.membase + UARTDR);
- xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
- sport->port.icount.tx++;
- }
+ if (sport->dma_tx_in_progress)
+ return;
- if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
- uart_write_wakeup(&sport->port);
+ sport->dma_tx_bytes = uart_circ_chars_pending(xmit);
- if (uart_circ_empty(xmit))
- writeb(readb(sport->port.membase + UARTCR5) | UARTCR5_TDMAS,
- sport->port.membase + UARTCR5);
+ if (xmit->tail < xmit->head) {
+ sport->dma_tx_nents = 1;
+ sg_init_one(sgl, xmit->buf + xmit->tail, sport->dma_tx_bytes);
+ } else {
+ 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);
+ }
- spin_unlock_irqrestore(&sport->port.lock, flags);
-}
+ ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+ if (!ret) {
+ dev_err(dev, "DMA mapping error for TX.\n");
+ return;
+ }
-static int lpuart_dma_tx(struct lpuart_port *sport, unsigned long count)
-{
- struct circ_buf *xmit = &sport->port.state->xmit;
- dma_addr_t tx_bus_addr;
-
- dma_sync_single_for_device(sport->port.dev, sport->dma_tx_buf_bus,
- UART_XMIT_SIZE, DMA_TO_DEVICE);
- sport->dma_tx_bytes = count & ~(sport->txfifo_size - 1);
- tx_bus_addr = sport->dma_tx_buf_bus + xmit->tail;
- sport->dma_tx_desc = dmaengine_prep_slave_single(sport->dma_tx_chan,
- tx_bus_addr, sport->dma_tx_bytes,
+ sport->dma_tx_desc = dmaengine_prep_slave_sg(sport->dma_tx_chan, sgl,
+ sport->dma_tx_nents,
DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
-
if (!sport->dma_tx_desc) {
- dev_err(sport->port.dev, "Not able to get desc for tx\n");
- return -EIO;
+ dma_unmap_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+ dev_err(dev, "Cannot prepare TX slave DMA!\n");
+ return;
}
sport->dma_tx_desc->callback = lpuart_dma_tx_complete;
sport->dma_tx_desc->callback_param = sport;
- sport->dma_tx_in_progress = 1;
+ sport->dma_tx_in_progress = true;
sport->dma_tx_cookie = dmaengine_submit(sport->dma_tx_desc);
dma_async_issue_pending(sport->dma_tx_chan);
- return 0;
-}
-
-static void lpuart_prepare_tx(struct lpuart_port *sport)
-{
- struct circ_buf *xmit = &sport->port.state->xmit;
- unsigned long count = CIRC_CNT_TO_END(xmit->head,
- xmit->tail, UART_XMIT_SIZE);
-
- if (!count)
- return;
-
- if (count < sport->txfifo_size)
- writeb(readb(sport->port.membase + UARTCR5) & ~UARTCR5_TDMAS,
- sport->port.membase + UARTCR5);
- else {
- writeb(readb(sport->port.membase + UARTCR5) | UARTCR5_TDMAS,
- sport->port.membase + UARTCR5);
- lpuart_dma_tx(sport, count);
- }
}
static void lpuart_dma_tx_complete(void *arg)
{
struct lpuart_port *sport = arg;
+ struct scatterlist *sgl = &sport->tx_sgl[0];
struct circ_buf *xmit = &sport->port.state->xmit;
unsigned long flags;
- async_tx_ack(sport->dma_tx_desc);
-
spin_lock_irqsave(&sport->port.lock, flags);
+ dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+
xmit->tail = (xmit->tail + sport->dma_tx_bytes) & (UART_XMIT_SIZE - 1);
- sport->dma_tx_in_progress = 0;
+
+ sport->port.icount.tx += sport->dma_tx_bytes;
+ sport->dma_tx_in_progress = false;
+ spin_unlock_irqrestore(&sport->port.lock, flags);
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&sport->port);
- lpuart_prepare_tx(sport);
+ if (waitqueue_active(&sport->dma_wait)) {
+ wake_up(&sport->dma_wait);
+ return;
+ }
+
+ spin_lock_irqsave(&sport->port.lock, flags);
+
+ if (!uart_circ_empty(xmit) && !uart_tx_stopped(&sport->port))
+ lpuart_dma_tx(sport);
spin_unlock_irqrestore(&sport->port.lock, flags);
}
+static int lpuart_dma_tx_request(struct uart_port *port)
+{
+ struct lpuart_port *sport = container_of(port,
+ struct lpuart_port, port);
+ struct dma_slave_config dma_tx_sconfig = {};
+ int ret;
+
+ dma_tx_sconfig.dst_addr = sport->port.mapbase + UARTDR;
+ dma_tx_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ dma_tx_sconfig.dst_maxburst = 1;
+ dma_tx_sconfig.direction = DMA_MEM_TO_DEV;
+ ret = dmaengine_slave_config(sport->dma_tx_chan, &dma_tx_sconfig);
+
+ if (ret) {
+ dev_err(sport->port.dev,
+ "DMA slave config failed, err = %d\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
static void lpuart_flush_buffer(struct uart_port *port)
{
struct lpuart_port *sport = container_of(port, struct lpuart_port, port);
+
if (sport->lpuart_dma_tx_use) {
+ if (sport->dma_tx_in_progress) {
+ dma_unmap_sg(sport->port.dev, &sport->tx_sgl[0],
+ sport->dma_tx_nents, DMA_TO_DEVICE);
+ sport->dma_tx_in_progress = false;
+ }
dmaengine_terminate_all(sport->dma_tx_chan);
- sport->dma_tx_in_progress = 0;
}
}
@@ -469,8 +484,8 @@ static void lpuart_start_tx(struct uart_port *port)
writeb(temp | UARTCR2_TIE, port->membase + UARTCR2);
if (sport->lpuart_dma_tx_use) {
- if (!uart_circ_empty(xmit) && !sport->dma_tx_in_progress)
- lpuart_prepare_tx(sport);
+ if (!uart_circ_empty(xmit) && !uart_tx_stopped(port))
+ lpuart_dma_tx(sport);
} else {
if (readb(port->membase + UARTSR1) & UARTSR1_TDRE)
lpuart_transmit_buffer(sport);
@@ -489,6 +504,29 @@ static void lpuart32_start_tx(struct uart_port *port)
lpuart32_transmit_buffer(sport);
}
+/* return TIOCSER_TEMT when transmitter is not busy */
+static unsigned int lpuart_tx_empty(struct uart_port *port)
+{
+ struct lpuart_port *sport = container_of(port,
+ struct lpuart_port, port);
+ unsigned char sr1 = readb(port->membase + UARTSR1);
+ unsigned char sfifo = readb(port->membase + UARTSFIFO);
+
+ if (sport->dma_tx_in_progress)
+ return 0;
+
+ if (sr1 & UARTSR1_TC && sfifo & UARTSFIFO_TXEMPT)
+ return TIOCSER_TEMT;
+
+ return 0;
+}
+
+static unsigned int lpuart32_tx_empty(struct uart_port *port)
+{
+ return (lpuart32_read(port->membase + UARTSTAT) & UARTSTAT_TC) ?
+ TIOCSER_TEMT : 0;
+}
+
static irqreturn_t lpuart_txint(int irq, void *dev_id)
{
struct lpuart_port *sport = dev_id;
@@ -662,12 +700,8 @@ static irqreturn_t lpuart_int(int irq, void *dev_id)
if (sts & UARTSR1_RDRF)
lpuart_rxint(irq, dev_id);
- if (sts & UARTSR1_TDRE) {
- if (sport->lpuart_dma_tx_use)
- lpuart_pio_tx(sport);
- else
- lpuart_txint(irq, dev_id);
- }
+ if (sts & UARTSR1_TDRE)
+ lpuart_txint(irq, dev_id);
return IRQ_HANDLED;
}
@@ -692,29 +726,6 @@ static irqreturn_t lpuart32_int(int irq, void *dev_id)
return IRQ_HANDLED;
}
-/* return TIOCSER_TEMT when transmitter is not busy */
-static unsigned int lpuart_tx_empty(struct uart_port *port)
-{
- struct lpuart_port *sport = container_of(port,
- struct lpuart_port, port);
- unsigned char sr1 = readb(port->membase + UARTSR1);
- unsigned char sfifo = readb(port->membase + UARTSFIFO);
-
- if (sport->dma_tx_in_progress)
- return 0;
-
- if (sr1 & UARTSR1_TC && sfifo & UARTSFIFO_TXEMPT)
- return TIOCSER_TEMT;
-
- return 0;
-}
-
-static unsigned int lpuart32_tx_empty(struct uart_port *port)
-{
- return (lpuart32_read(port->membase + UARTSTAT) & UARTSTAT_TC) ?
- TIOCSER_TEMT : 0;
-}
-
static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)
{
struct tty_port *port = &sport->port.state->port;
@@ -890,18 +901,6 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
return 0;
}
-static void lpuart_dma_tx_free(struct uart_port *port)
-{
- struct lpuart_port *sport = container_of(port,
- struct lpuart_port, port);
-
- dma_unmap_single(sport->port.dev, sport->dma_tx_buf_bus,
- UART_XMIT_SIZE, DMA_TO_DEVICE);
-
- sport->dma_tx_buf_bus = 0;
- sport->dma_tx_buf_virt = NULL;
-}
-
static void lpuart_dma_rx_free(struct uart_port *port)
{
struct lpuart_port *sport = container_of(port,
@@ -1061,44 +1060,6 @@ static void lpuart32_setup_watermark(struct lpuart_port *sport)
lpuart32_write(ctrl_saved, sport->port.membase + UARTCTRL);
}
-static int lpuart_dma_tx_request(struct uart_port *port)
-{
- struct lpuart_port *sport = container_of(port,
- struct lpuart_port, port);
- struct dma_slave_config dma_tx_sconfig;
- dma_addr_t dma_bus;
- unsigned char *dma_buf;
- int ret;
-
- dma_bus = dma_map_single(sport->dma_tx_chan->device->dev,
- sport->port.state->xmit.buf,
- UART_XMIT_SIZE, DMA_TO_DEVICE);
-
- if (dma_mapping_error(sport->dma_tx_chan->device->dev, dma_bus)) {
- dev_err(sport->port.dev, "dma_map_single tx failed\n");
- return -ENOMEM;
- }
-
- dma_buf = sport->port.state->xmit.buf;
- dma_tx_sconfig.dst_addr = sport->port.mapbase + UARTDR;
- dma_tx_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
- dma_tx_sconfig.dst_maxburst = sport->txfifo_size;
- dma_tx_sconfig.direction = DMA_MEM_TO_DEV;
- ret = dmaengine_slave_config(sport->dma_tx_chan, &dma_tx_sconfig);
-
- if (ret < 0) {
- dev_err(sport->port.dev,
- "Dma slave config failed, err = %d\n", ret);
- return ret;
- }
-
- sport->dma_tx_buf_virt = dma_buf;
- sport->dma_tx_buf_bus = dma_bus;
- sport->dma_tx_in_progress = 0;
-
- return 0;
-}
-
static void rx_dma_timer_init(struct lpuart_port *sport)
{
setup_timer(&sport->lpuart_timer, lpuart_timer_func,
@@ -1151,6 +1112,7 @@ static int lpuart_startup(struct uart_port *port)
}
if (sport->dma_tx_chan && !lpuart_dma_tx_request(port)) {
+ init_waitqueue_head(&sport->dma_wait);
sport->lpuart_dma_tx_use = true;
temp = readb(port->membase + UARTCR5);
writeb(temp | UARTCR5_TDMAS, port->membase + UARTCR5);
@@ -1220,8 +1182,15 @@ static void lpuart_shutdown(struct uart_port *port)
lpuart_dma_rx_free(&sport->port);
}
- if (sport->lpuart_dma_tx_use)
- lpuart_dma_tx_free(&sport->port);
+ if (sport->lpuart_dma_tx_use) {
+ if (wait_event_interruptible(sport->dma_wait,
+ !sport->dma_tx_in_progress) != false) {
+ sport->dma_tx_in_progress = false;
+ dmaengine_terminate_all(sport->dma_tx_chan);
+ }
+
+ lpuart_stop_tx(port);
+ }
}
static void lpuart32_shutdown(struct uart_port *port)
--
2.9.0
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