""" The mini-UART on BCM283x is doubly crippled - it has 8-byte FIFOs and the THRE bit indicates that the TX FIFO is not-full rather than empty. The optimisation to enable the use of the FIFO assumes that it is safe to write fifosize bytes whenever THRE is set, but the BCM283x quirk (indicated by the presence of UART_CAP_MINI) makes it necessary to check the FIFO state after each byte. See: https://github.com/raspberrypi/linux/issues/4849 """ Thanks to Phil Elwell for reporting the issue and providing the original patch. Reported-by: Phil Elwell <phil@xxxxxxxxxxxxxxx> Co-author: Phil Elwell <phil@xxxxxxxxxxxxxxx> Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx> --- drivers/tty/serial/8250/8250_port.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index d3a93e5d55f7..4acf620be241 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3409,6 +3409,11 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, } use_fifo = (up->capabilities & UART_CAP_FIFO) && + /* + * BCM283x requires to check the fifo + * after each byte. + */ + !(up->capabilities & UART_CAP_MINI) && up->tx_loadsz > 1 && (up->fcr & UART_FCR_ENABLE_FIFO) && /* -- 2.35.1
