serial: tegra: Correct shutdown of UARTs

There are two issues in the shutdown path of the UARTs which are:
1. The function tegra_uart_shutdown() calls tegra_uart_flush_buffer()
   to stop DMA TX transfers. However, tegra_uart_flush_buffer() is
   called after the DMA channels have already been freed and so actually
   does nothing.
2. The function that frees the DMA channels
   (tegra_uart_dma_channel_free()), unmaps the dma buffer before
   freeing the DMA channel and does not ensure the DMA has been
   stopped.

Resolve this by fixing the code in tegra_uart_dma_channel_free() to
ensure the DMA is stopped, free the DMA channel and then unmap the DMA
buffer. Finally, remove the unnecessary call to tegra_uart_flush_buffer().

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 987c05665e626f26a5a6ad5e92d8e79eaa930c45..96378da9aefce841270f2ca2bcfdd07a3427abe0 100644 (file)
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -1020,24 +1020,23 @@ scrub:
 static void tegra_uart_dma_channel_free(struct tegra_uart_port *tup,
                bool dma_to_memory)
 {
-       struct dma_chan *dma_chan;
-
        if (dma_to_memory) {
+               dmaengine_terminate_all(tup->rx_dma_chan);
+               dma_release_channel(tup->rx_dma_chan);
                dma_free_coherent(tup->uport.dev, TEGRA_UART_RX_DMA_BUFFER_SIZE,
                                tup->rx_dma_buf_virt, tup->rx_dma_buf_phys);
-               dma_chan = tup->rx_dma_chan;
                tup->rx_dma_chan = NULL;
                tup->rx_dma_buf_phys = 0;
                tup->rx_dma_buf_virt = NULL;
        } else {
+               dmaengine_terminate_all(tup->tx_dma_chan);
+               dma_release_channel(tup->tx_dma_chan);
                dma_unmap_single(tup->uport.dev, tup->tx_dma_buf_phys,
                        UART_XMIT_SIZE, DMA_TO_DEVICE);
-               dma_chan = tup->tx_dma_chan;
                tup->tx_dma_chan = NULL;
                tup->tx_dma_buf_phys = 0;
                tup->tx_dma_buf_virt = NULL;
        }
-       dma_release_channel(dma_chan);
 }
 
 static int tegra_uart_startup(struct uart_port *u)
@@ -1104,8 +1103,6 @@ static void tegra_uart_shutdown(struct uart_port *u)
        tegra_uart_dma_channel_free(tup, true);
        tegra_uart_dma_channel_free(tup, false);
        free_irq(u->irq, tup);
-
-       tegra_uart_flush_buffer(u);
 }
 
 static void tegra_uart_enable_ms(struct uart_port *u)