linux.git/drivers/tty/serial/serial-tegra.c, branch v4.7

serial: tegra: Remove unused variable

2016-04-30T16:26:55+00:00

The local mcr variable is never used in the tegra_uart_set_mctrl()
function, so it should be removed.

Signed-off-by: Thierry Reding 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Add helper function for handling RX buffer

2015-10-18T04:07:57+00:00

In the tegra UART driver there are three places where the RX DMA buffer
is handled and pushed up to the tty layer. In all three instances the
same functions are called and so instead of duplicating the code in three
places, move this code to a new helper function and use this new function.

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Remove redundant code and check in tegra_uart_stop_rx()

2015-10-18T04:07:57+00:00

The serial-tegra driver always uses DMA and hence the driver always
allocates DMA channels. Therefore, the test to see if the RX DMA channel
is initialised in tegra_uart_stop_rx() is unnecessary and so remove
the test and the code that corresponds to the case where the RX DMA
channel is not initialised. Please note that the call to
tegra_uart_stop_rx() should always be before the call to
tegra_uart_shutdown() which will uninitialise the RX DMA channel.

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Remove unnecessary return statements

2015-10-18T04:07:57+00:00

Some functions in the serial-tegra driver have unnecessary return
statements at the end of a void function and so remove them.

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Handle another RX race condition

2015-10-18T04:07:57+00:00

Commit 853a699739fe ("serial: tegra: handle race condition on uart rx
side") attempted to fix a race condition between the RX end of
transmission interrupt and RX DMA completion callback. Despite this
fix there is still another case where these two paths can race and
result in duplicated data. The race condition is as follows:

1. DMA completion interrupt occurs and schedules tasklet to call DMA
   callback.
2. DMA callback for the UART driver starts to execute. This will copy
   the data from the DMA buffer and restart the DMA. This is done under
   uart port spinlock.
3. During the callback, UART interrupt is raised for end of receive. The
   UART ISR runs and waits to acquire port spinlock held by the DMA
   callback.
4. DMA callback gives up spinlock after copying the data, but before
   restarting DMA.
5. UART ISR acquires the spin lock and reads the same DMA buffer because
   DMA has not been restarted yet.

The release of the spinlock during the DMA callback was introduced by
commit 9b88748b362c ("tty: serial: tegra: drop uart_port->lock before
calling tty_flip_buffer_push()") to fix a spinlock lock-up issue when
calling tty_flip_buffer_push(). However, since then commit a9c3f68f3cd8
("tty: Fix low_latency BUG") migrated tty_flip_buffer_push() to always
use a workqueue, allowing tty_flip_buffer_push() to be called from
within atomic sections. Therefore, we can remove the unlocking of the
spinlock from the DMA callback and UART ISR and this will ensure that
the race condition no longer occurs.

Reported-by: Christopher Freeman 
Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Fix memory leak on DMA setup failure

2015-05-24T19:53:44+00:00

If the call to dmaengine_slave_config() fails, then the DMA buffer will
not be freed/unmapped. Fix this by moving the code that stores the
address of the buffer in the tegra_uart_port structure to before the
call to dmaengine_slave_config().

Reported-by: Alexandre Courbot 
Signed-off-by: Jon Hunter 
Reviewed-by: Alexandre Courbot 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Correct error handling on DMA setup

2015-05-10T17:12:19+00:00

Function tegra_uart_dma_channel_allocate() does not check that
dma_map_single() mapped the DMA buffer correctly. Add a check for this
and appropriate error handling.

Furthermore, if dmaengine_slave_config() (called by
tegra_uart_dma_channel_allocate()) fails, then memory allocated/mapped
is not freed/unmapped. Therefore, call tegra_uart_dma_channel_free()
instead of just dma_release_channel() if  dmaengine_slave_config() fails.

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Correct shutdown of UARTs

2015-05-10T17:12:19+00:00

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 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Fix cookie used by TX channel

2015-05-10T17:12:19+00:00

The DMA cookie for the RX channel is being used by the TX channel.
Therefore, fix driver to use the correct DMA cookie for the TX channel.

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman

serial: tegra: Use unsigned types for RX and TX byte counts

2015-05-10T17:12:19+00:00

The function tty_insert_flip_string() takes an argument "size" which is
of type size_t. This is an unsigned type. Update the count,
rx_bytes_requested and tx_bytes_requested in the tegra serial driver to
be unsigned integers so that an unsigned type is passed to
tty_insert_flip_string().

Signed-off-by: Jon Hunter 
Signed-off-by: Greg Kroah-Hartman