6.6-stable review patch. If anyone has any objections, please let me know.
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From: Sam Ravnborg sam@ravnborg.org
[ Upstream commit c6dcd8050fb7c2efec6946ae9c49bc186b0a7475 ]
When using a leon kernel with qemu there where no console prompt. The root cause is the handling of the fifo size in the tx part of the apbuart driver.
The qemu uart driver only have a very rudimentary status handling and do not report the number of chars queued in the tx fifo in the status register. So the driver ends up with a fifo size of 1.
In the tx path the fifo size is divided by 2 - resulting in a fifo size of zero.
The original implementation would always try to send one char, but after the introduction of uart_port_tx_limited() the fifo size is respected even for the first char.
There seems to be no good reason to divide the fifo size with two - so remove this. It looks like something copied from the original amba driver.
With qemu we now have a minimum fifo size of one char, so we show the prompt.
Signed-off-by: Sam Ravnborg sam@ravnborg.org Fixes: d11cc8c3c4b6 ("tty: serial: use uart_port_tx_limited()") Cc: Andreas Larsson andreas@gaisler.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jiri Slaby jirislaby@kernel.org Cc: linux-serial@vger.kernel.org Cc: sparclinux@vger.kernel.org Link: https://lore.kernel.org/r/20231226121607.GA2622970@ravnborg.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/apbuart.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/apbuart.c b/drivers/tty/serial/apbuart.c index d7658f380838..d3cb341f2c55 100644 --- a/drivers/tty/serial/apbuart.c +++ b/drivers/tty/serial/apbuart.c @@ -122,7 +122,7 @@ static void apbuart_tx_chars(struct uart_port *port) { u8 ch;
- uart_port_tx_limited(port, ch, port->fifosize >> 1, + uart_port_tx_limited(port, ch, port->fifosize, true, UART_PUT_CHAR(port, ch), ({}));