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authorHuang Shijie <b32955@freescale.com>2013-10-15 11:23:40 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-17 05:25:30 +0400
commit7cb92fd2a0515ea2ae905bf6c90a84aed2b78ffb (patch)
tree03787b19a1187f87a3d12b99b098fd40a98018d7 /drivers/tty
parentf0ef8834b280ebb6c271f155ea040bf4af6c1881 (diff)
downloadlinux-7cb92fd2a0515ea2ae905bf6c90a84aed2b78ffb.tar.xz
serial: imx: optimization: remove the workqueues for DMA
I worried that the delay of the sdma_run_channel0() maybe too long for interrupt context, so I added the workqueues for RX/TX DMA. But tested with bluetooth device, I find that the delay of sdma_run_channel0() is about 8us (tested in imx6dl sabreauto board). I think the delay is acceptable. This patch removes the RX/TX workqueues for DMA, it makes the code more clear. Signed-off-by: Huang Shijie <b32955@freescale.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/imx.c54
1 files changed, 10 insertions, 44 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 13c2c2d09cac..bb84f8d4c54e 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -223,8 +223,7 @@ struct imx_port {
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 tx_bytes;
unsigned int dma_tx_nents;
wait_queue_head_t dma_wait;
};
@@ -505,32 +504,23 @@ static void dma_tx_callback(void *data)
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)
+static void imx_dma_tx(struct imx_port *sport)
{
- 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 = dmaengine_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 && xmit->head > 0) {
sport->dma_tx_nents = 2;
@@ -542,7 +532,6 @@ static void dma_tx_work(struct work_struct *w)
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) {
@@ -609,11 +598,7 @@ static void imx_start_tx(struct uart_port *port)
}
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);
+ imx_dma_tx(sport);
return;
}
@@ -732,6 +717,7 @@ out:
return IRQ_HANDLED;
}
+static int start_rx_dma(struct imx_port *sport);
/*
* If the RXFIFO is filled with some data, and then we
* arise a DMA operation to receive them.
@@ -750,7 +736,7 @@ static void imx_dma_rxint(struct imx_port *sport)
writel(temp, sport->port.membase + UCR1);
/* tell the DMA to receive the data. */
- schedule_work(&sport->tsk_dma_rx);
+ start_rx_dma(sport);
}
}
@@ -872,22 +858,6 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
}
#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;
@@ -919,6 +889,7 @@ 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 tty_port *port = &sport->port.state->port;
struct dma_tx_state state;
enum dma_status status;
unsigned int count;
@@ -931,8 +902,10 @@ static void dma_rx_callback(void *data)
dev_dbg(sport->port.dev, "We get %d bytes.\n", count);
if (count) {
- sport->rx_bytes = count;
- schedule_work(&sport->tsk_dma_rx);
+ tty_insert_flip_string(port, sport->rx_buf, count);
+ tty_flip_buffer_push(port);
+
+ start_rx_dma(sport);
} else
imx_rx_dma_done(sport);
}
@@ -1014,7 +987,6 @@ static int imx_uart_dma_init(struct imx_port *sport)
ret = -ENOMEM;
goto err;
}
- sport->rx_bytes = 0;
/* Prepare for TX : */
sport->dma_chan_tx = dma_request_slave_channel(dev, "tx");
@@ -1045,11 +1017,7 @@ err:
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 */
@@ -1070,7 +1038,6 @@ static void imx_enable_dma(struct imx_port *sport)
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);
@@ -1088,7 +1055,6 @@ static void imx_disable_dma(struct imx_port *sport)
writel(temp, sport->port.membase + UCR4);
sport->dma_is_enabled = 0;
- port->low_latency = 0;
}
/* half the RX buffer size */