[PATCH 4/6] Serial: AT91: Enable tx dma
Elen Song
elen.song at atmel.com
Mon Oct 29 05:10:37 EDT 2012
Tx dma will setup a single transfer,
when transfer end, it will call atmel_dma_tx_complete to do finish stuff.
Signed-off-by: Elen Song <elen.song at atmel.com>
---
drivers/tty/serial/atmel_serial.c | 99 +++++++++++++++++++++++++++++++++++++
1 file changed, 99 insertions(+)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index c02a919..352ef4a 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -590,6 +590,39 @@ static void atmel_tx_chars(struct uart_port *port)
UART_PUT_IER(port, atmel_port->tx_done_mask);
}
+static void atmel_dma_tx_complete(void *arg)
+{
+ struct atmel_uart_port *atmel_port = arg;
+ struct uart_port *port = &atmel_port->uart;
+ struct circ_buf *xmit = &port->state->xmit;
+ struct dma_chan *chan = atmel_port->chan_tx;
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->lock, flags);
+
+ if (chan)
+ dmaengine_terminate_all(chan);
+ xmit->tail += sg_dma_len(&atmel_port->sg_tx);
+ xmit->tail &= UART_XMIT_SIZE - 1;
+
+ port->icount.tx += sg_dma_len(&atmel_port->sg_tx);
+
+ spin_lock_irq(&atmel_port->lock_tx);
+ async_tx_ack(atmel_port->desc_tx);
+ atmel_port->cookie_tx = -EINVAL;
+ atmel_port->desc_tx = NULL;
+ spin_unlock_irq(&atmel_port->lock_tx);
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(port);
+
+ /* Do we really need this? */
+ if (!uart_circ_empty(xmit))
+ tasklet_schedule(&atmel_port->tasklet);
+
+ spin_unlock_irqrestore(&port->lock, flags);
+}
+
static void atmel_tx_dma_release(struct atmel_uart_port *atmel_port)
{
struct dma_chan *chan = atmel_port->chan_tx;
@@ -602,6 +635,70 @@ static void atmel_tx_dma_release(struct atmel_uart_port *atmel_port)
}
}
+/*
+ * Called from tasklet with TXRDY interrupt is disabled.
+ */
+static void atmel_tx_dma(struct uart_port *port)
+{
+ struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+ struct circ_buf *xmit = &port->state->xmit;
+ struct dma_chan *chan = atmel_port->chan_tx;
+ struct dma_async_tx_descriptor *desc;
+ struct scatterlist *sg = &atmel_port->sg_tx;
+
+ /* Make sure we have an idle channel */
+ if (atmel_port->desc_tx != NULL)
+ return;
+
+ if (!uart_circ_empty(xmit) && !uart_tx_stopped(port)) {
+ /*
+ * DMA is idle now.
+ * Port xmit buffer is already mapped,
+ * and it is one page... Just adjust
+ * offsets and lengths. Since it is a circular buffer,
+ * we have to transmit till the end, and then the rest.
+ * Take the port lock to get a
+ * consistent xmit buffer state.
+ */
+ sg->offset = xmit->tail & (UART_XMIT_SIZE - 1);
+ sg_dma_address(sg) = (sg_dma_address(sg) &
+ ~(UART_XMIT_SIZE - 1))
+ + sg->offset;
+ sg_dma_len(sg) = CIRC_CNT_TO_END(xmit->head,
+ xmit->tail,
+ UART_XMIT_SIZE);
+ BUG_ON(!sg_dma_len(sg));
+
+ desc = dmaengine_prep_slave_sg(chan,
+ sg,
+ atmel_port->sg_len_tx,
+ DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT |
+ DMA_CTRL_ACK);
+ if (!desc) {
+ dev_err(port->dev, "Failed to send via dma!\n");
+ return;
+ }
+
+ dma_sync_sg_for_device(port->dev, sg, 1, DMA_MEM_TO_DEV);
+
+ atmel_port->desc_tx = desc;
+ desc->callback = atmel_dma_tx_complete;
+ desc->callback_param = atmel_port;
+ atmel_port->cookie_tx = dmaengine_submit(desc);
+
+ dma_async_issue_pending(chan);
+ } else {
+ if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
+ /* DMA done, stop TX, start RX for RS485 */
+ atmel_start_rx(port);
+ }
+ }
+
+ if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+ uart_write_wakeup(port);
+}
+
static bool filter(struct dma_chan *chan, void *slave)
{
struct at_dma_slave *sl = slave;
@@ -991,6 +1088,8 @@ static void atmel_tasklet_func(unsigned long data)
if (atmel_use_pdc_tx(port))
atmel_tx_pdc(port);
+ else if (atmel_use_dma_tx(port))
+ atmel_tx_dma(port);
else
atmel_tx_chars(port);
--
1.7.9.5
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