Revert "serial: imx: remove the DMA wait queue"

This reverts commit e2f2786606d49d3aae545c61c04757a64cf7e5f0.

Huang reports that this patch is broken and should be reverted.

Cc: Huang Shijie <b32955@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 3b706add81a9e82a2d24851efb13433651a055a4..e2f93874989b5ac61dac61fa60bb199ef74bc9a9 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -225,6 +225,7 @@ struct imx_port {
        void                    *rx_buf;
        unsigned int            tx_bytes;
        unsigned int            dma_tx_nents;
+       wait_queue_head_t       dma_wait;
 };
 
 struct imx_port_ucrs {
@@ -415,10 +416,12 @@ static void imx_stop_tx(struct uart_port *port)
                return;
        }
 
-       if (sport->dma_is_enabled && sport->dma_is_txing) {
-               dmaengine_terminate_all(sport->dma_chan_tx);
-               sport->dma_is_txing = 0;
-       }
+       /*
+        * 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);
@@ -432,10 +435,12 @@ static void imx_stop_rx(struct uart_port *port)
        struct imx_port *sport = (struct imx_port *)port;
        unsigned long temp;
 
-       if (sport->dma_is_enabled && sport->dma_is_rxing) {
-               dmaengine_terminate_all(sport->dma_chan_rx);
-               sport->dma_is_rxing = 0;
-       }
+       /*
+        * 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);
@@ -496,6 +501,12 @@ static void dma_tx_callback(void *data)
        dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
 
        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;
+       }
 }
 
 static void imx_dma_tx(struct imx_port *sport)
@@ -868,6 +879,10 @@ static void imx_rx_dma_done(struct imx_port *sport)
        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);
 }
 
 /*
@@ -1014,6 +1029,8 @@ static void imx_enable_dma(struct imx_port *sport)
 {
        unsigned long temp;
 
+       init_waitqueue_head(&sport->dma_wait);
+
        /* set UCR1 */
        temp = readl(sport->port.membase + UCR1);
        temp |= UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN |
@@ -1205,13 +1222,10 @@ static void imx_shutdown(struct uart_port *port)
        unsigned long flags;
 
        if (sport->dma_is_enabled) {
-               /*
-                * The upper layer may does not call the @->stop_tx and
-                * @->stop_rx, so we call them ourselves.
-                */
-               imx_stop_tx(port);
+               /* 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);
        }