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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>
This commit is contained in:
Huang Shijie 2013-10-15 15:23:40 +08:00 committed by Greg Kroah-Hartman
parent f0ef8834b2
commit 7cb92fd2a0
1 changed files with 10 additions and 44 deletions
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54
drivers/tty/serial/imx.c
View File

@ -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 */