[PATCH v6 0/1] serial/8250: Use fifo in 8250 console driver

[Wander Lairson Costa]

This is v7 of the serial fifo patch. In relation to the previous
reverted patch, I describe the main changes in the "What changed from
v3" section.

What changed from v6
--------------------

* Add a comment on why we are using tx_loadsz instead of fifosize.

What changed from v5
--------------------

* Fixed a typo in patch patch "port-state" becomes "port->state".

What changed from v4
--------------------

* It squashes all the patches in a single patch
* It adds `port-state &&` check in the `use_fifo` condition as a
* preventive measure.

What changed from v3
--------------------

* Reads the FCR value from the port struct. The earlier patch
erroneously read the value from the controller, but FCR is a write-only
register. Thanks to Jiri Slaby for point this out.

* Use tx_loadsz as the transmitter fifo size. We previously used the
port->fifosize field, which caused data loss in some controllers. Thanks
Jon Hunter for the bug report.

* Exclude the BCM283x from fifo write. This is based on Phil Elwell's
original patch [1].

* Check if the port is initialized before write through fifo.
The serial driver set the value of uart_8250_port.fcr in the function
serial8250_config_port, but only writes the value to the controller
register later in the initalization code. That opens a small window in
which is not safe to use the fifo for console write. Unfortunately, I
lost track of who originally reported the issue. If s/he is reading
this, please speak up so I can give you the due credit.

[1] https://lore.kernel.org/all/20220126141124.4086065-1-phil@xxxxxxxxxxxxxxx/

Wander Lairson Costa (1):
  serial/8250: Use fifo in 8250 console driver

 drivers/tty/serial/8250/8250_port.c | 68 ++++++++++++++++++++++++++---
 1 file changed, 62 insertions(+), 6 deletions(-)

-- 
2.35.1