[PATCH v2 0/4] serial: implement flow control for ASPEED VUART driver

[Jeremy Kerr]

This series implements flow control for the ASPEED VUART driver. This
hardware is slightly unusual in that the RX data rate can quickly
overwhelm the flip buffer code, so the ldisc-driven throttle/unthrottle
mechanisms don't entirely solve the problem.

To do this, we have a couple of minor changes to the tty core to allow
tty drivers to do more explicit flow control.

Then, we implement the standard throttle mechanism, and augment it with
a fast-path to throttle if we overrun the flip buffers before the ldisc
has had a chance to run.

Questions and comments most welcome; I'm fairly new to the tty layer.

Cheers,


Jeremy

--
v2:
 - rebase onto tty-next, dropping applied proc patch
 - 1/4 simplify status mask checks
 - 4/4 Use updated timer API, fix text wrap


Jeremy Kerr (4):
  serial: Introduce UPSTAT_SYNC_FIFO for synchronised FIFOs
  serial/8250: export serial8250_read_char
  serial/aspeed-vuart: Implement rx throttling
  serial/aspeed-vuart: Implement quick throttle mechanism

 drivers/tty/serial/8250/8250_aspeed_vuart.c | 124 ++++++++++++++++++++++++++++
 drivers/tty/serial/8250/8250_port.c         |   3 +-
 drivers/tty/serial/serial_core.c            |   4 +-
 include/linux/serial_8250.h                 |   1 +
 include/linux/serial_core.h                 |   1 +
 5 files changed, 130 insertions(+), 3 deletions(-)

-- 
2.14.1