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  1. 14 12月, 2015 6 次提交
  3. 18 10月, 2015 1 次提交
  5. 05 9月, 2015 5 次提交
  7. 05 8月, 2015 5 次提交
  9. 24 7月, 2015 1 次提交
  11. 25 5月, 2015 12 次提交
  13. 20 5月, 2015 1 次提交
  15. 10 5月, 2015 1 次提交
  17. 07 5月, 2015 2 次提交
  19. 11 3月, 2015 1 次提交
  21. 07 3月, 2015 3 次提交
    • J
      drivers/tty: amba: defer DMA probe until the DMA channel is required. · 1c9be310
      由 Jorge Ramirez-Ortiz 提交于 
      Fix a race condition that happens when device_initcall(pl011_dma_initicall)
is executed before all the devices have been probed - this issue was observed on
a hisi_6220 SoC (HiKey board from Linaro).

The deferred driver probing framework relies on late_initcall to trigger
deferred probes so it is just possible that, even with a valid DMA driver ready
to be loaded, we fail to synchronize with it.

The proposed implementation delays probing the DMA until dma_startup.

As this is invoked on port startup and port resume - but DMA probing is only
required once - we avoid calling multiple times using a new field in
uart_amba_port to track this scenario.

This commit allows for subsequent attempts to associate an external DMA if the
DMA driver itself is not available (but present in the deferred probe pending
list).
Signed-off-by: NJorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      1c9be310
    • D
      serial/amba-pl011: Leave the TX IRQ alone when the UART is not open · f2ee6dfa
      由 Dave Martin 提交于 
      Getting the TX IRQ re-asserted from scratch can be inefficient in
some setups.

This patch avoids clearing the TX IRQ across pl011_shutdown()...
pl011_startup(), so that if the port is closed and reopened, the
IRQ will still work afterwards without having to bootstrap it again.

The TX IRQ continues to be masked in IMSC when the UART is not in
use.
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Tested-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      f2ee6dfa
    • D
      serial/amba-pl011: Activate TX IRQ passively · 734745ca
      由 Dave Martin 提交于 
      The current PL011 driver transmits a dummy character when the UART
is opened, to assert the TX IRQ for the first time
(see pl011_startup()).  The UART is put in loopback mode temporarily,
so the receiver presumably shouldn't see anything.

However...

At least some platforms containing a PL011 send characters down the
wire even when loopback mode is enabled.  This means that a
spurious NUL character may be seen at the receiver when the PL011 is
opened through the TTY layer.

The current code also temporarily sets the baud rate to maximum and
the character width to the minimum, to that the dummy TX completes
as quickly as possible.  If this is seen by the receiver it will
result in a framing error and can knock the receiver out of sync --
turning subsequent output into garbage until synchronisation
is reestablished.  (Particularly problematic during boot with systemd.)

To avoid spurious transmissions, this patch removes assumptions about
whether the TX IRQ will fire until at least one TX IRQ has been seen.

Instead, the UART will unmask the TX IRQ and then slow-start via
polling and timer-based soft IRQs initially.  If the TTY layer writes
enough data to fill the FIFO to the interrupt threshold in one go,
the TX IRQ should assert, at which point the driver changes to
fully interrupt-driven TX.

In this way, the TX IRQ is activated as a side-effect instead of
being done deliberately.

This should also mean that the driver works on the SBSA Generic
UART[1] (a cut-down PL011) without invasive changes.  The Generic
UART lacks some features needed for the dummy TX approach to work
(FIFO disabling and loopback).

[1] Server Base System Architecture (ARM-DEN-0029-v2.3)
    http://infocenter.arm.com/
    (click-thru required :/)
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Tested-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      734745ca
  23. 08 11月, 2014 2 次提交