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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>
This commit is contained in:
Jon Hunter 2015-05-05 15:17:58 +01:00 committed by Greg Kroah-Hartman
parent 49433c802c
commit d92aca3a76
1 changed files with 4 additions and 7 deletions
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11
drivers/tty/serial/serial-tegra.c
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@ -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)