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  1. 18 Oct, 2015 9 commits
    • Peter Hurley's avatar
      tty: Remove tty_wait_until_sent_from_close() · 79c1faa4
      Peter Hurley authored 
      tty_wait_until_sent_from_close() drops the tty lock while waiting
for the tty driver to finish sending previously accepted data (ie.,
data remaining in its write buffer and transmit fifo).

tty_wait_until_sent_from_close() was added by commit a57a7bf3
("TTY: define tty_wait_until_sent_from_close") to prevent the entire
tty subsystem from being unable to open new ttys while waiting for
one tty to close while output drained.

However, since commit 0911261d ("tty: Don't take tty_mutex for tty
count changes"), holding a tty lock while closing does not prevent other
ttys from being opened/closed/hung up, but only prevents lifetime event
changes for the tty under lock.

Holding the tty lock while waiting for output to drain does prevent
parallel non-blocking opens (O_NONBLOCK) from advancing or returning
while the tty lock is held. However, all parallel opens _already_
block even if the tty lock is dropped while closing and the parallel
open advances. Blocking in open has been in mainline since at least 2.6.29
(see tty_port_block_til_ready(); note the test for O_NONBLOCK is _after_
the wait while ASYNC_CLOSING).

IOW, before this patch a non-blocking open will sleep anyway for the
_entire_ duration of a parallel hardware shutdown, and when it wakes, the
error return will cause a release of its tty, and it will restart with
a fresh attempt to open. Similarly with a blocking open that is already
waiting; when it's woken, the hardware shutdown has already completed
to ASYNC_INITIALIZED is not set, which forces a release and restart as
well.

So, holding the tty lock across the _entire_ close (which is what this
patch does), even while waiting for output to drain, is equivalent to
the current outcome wrt parallel opens.

Cc: Alan Cox <alan@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Karsten Keil <isdn@linux-pingi.de>
CC: linuxppc-dev@lists.ozlabs.org
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      79c1faa4
    • Jon Hunter's avatar
      serial: tegra: Add helper function for handling RX buffer · 32ede4a5
      Jon Hunter authored 
      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: default avatarJon Hunter <jonathanh@nvidia.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      32ede4a5
    • Jon Hunter's avatar
      serial: tegra: Remove redundant code and check in tegra_uart_stop_rx() · b0e066cc
      Jon Hunter authored 
      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: default avatarJon Hunter <jonathanh@nvidia.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b0e066cc
    • Jon Hunter's avatar
      serial: tegra: Remove unnecessary return statements · 2230a947
      Jon Hunter authored 
      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: default avatarJon Hunter <jonathanh@nvidia.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      2230a947
    • Jon Hunter's avatar
      serial: tegra: Handle another RX race condition · 2a24bb28
      Jon Hunter authored 
      Commit 853a6997 ("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 9b88748b ("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 a9c3f68f
("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: default avatarChristopher Freeman <cfreeman@nvidia.com>
Signed-off-by: default avatarJon Hunter <jonathanh@nvidia.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      2a24bb28
    • Peter Hurley's avatar
      serial: 8250_omap: Remove RTS clear · 0abcc6df
      Peter Hurley authored 
      Clearing UART_MCR_RTS or UART_MCR_XONANY is unnecessary; these bits
are never set in the shadow mcr. The RTS clear is especially confusing.
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      0abcc6df
    • Scott Wood's avatar
      serial: Enable Freescale 16550 workaround on arm · d43b54d2
      Scott Wood authored 
      The same serial hardware is present on LS2080A which is arm64, and
LS1021A which is arm32, so don't limit the workaround to PPC.

Unlike PPC which uses arch/powerpc/kernel/legacy_serial.c, the ARM
targets use drivers/tty/serial/of_serial.c, so add the handle_irq
override check there as well.
Signed-off-by: default avatarScott Wood <scottwood@freescale.com>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      d43b54d2
    • Andreas Werner's avatar
      tty: serial: men_z135_uart.c: use mcb memory region size instead of hardcoded one · 37f06799
      Andreas Werner authored 
      There is no need to hardcode the MEN_Z135_MEM_SIZE. The MCB subsystem
already knowns the size which is located in the chameleon table.
MCB parse the chameleon table to get the resources of each IP and provide
the mcb_request_mem function to get those resources.

Use mcb_request_mem to get the resources. This function also takes care of
the memory region naming allocated by the driver for each of the instances.
Signed-off-by: default avatarAndreas Werner <andy@wernerandy.de>
Acked-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      37f06799
    • Andre Przywara's avatar
      serial: atmel: fix compiler warning on address cast · 270c2ade
      Andre Przywara authored 
      Turning on KVM and LPAE support on top of a multi_v7_defconfig will
produce a compiler warning in the Atmel serial driver:
drivers/tty/serial/atmel_serial.c: In function 'atmel_verify_port':
drivers/tty/serial/atmel_serial.c:2299:6: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  if ((void *)port->mapbase != ser->iomem_base)
      ^

Fix that by using the cast on the right hand side instead, as similar
code already does in other drivers.
Signed-off-by: default avatarAndre Przywara <andre.przywara@arm.com>
Acked-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      270c2ade
  3. 12 Oct, 2015 1 commit
  5. 11 Oct, 2015 8 commits
  7. 10 Oct, 2015 12 commits
  9. 09 Oct, 2015 10 commits
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