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>

1 files changed, 28 insertions, 14 deletions

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 3b706add81a9..e2f93874989b 100644
--- 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);
         }