tty: serial: use uart_port_tx_limited()

uart_port_tx_limited() is a new helper to send characters to the device.
Use it in these drivers.

mux.c also needs to define tx_done(). But I'm not sure if the driver
really wants to wait for all the characters to dismiss from the HW fifo
at this code point. Hence I marked this as FIXME.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: "Pali Rohár" <pali@kernel.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang7@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: linux-riscv@lists.infradead.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20221004104927.14361-4-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 29 deletions

diff --git a/drivers/tty/serial/apbuart.c b/drivers/tty/serial/apbuart.c
index 450f4edfda0f..915ee4b0d594 100644
--- a/drivers/tty/serial/apbuart.c
+++ b/drivers/tty/serial/apbuart.c
@@ -122,36 +122,12 @@ static void apbuart_rx_chars(struct uart_port *port)
 
 static void apbuart_tx_chars(struct uart_port *port)
 {
-	struct circ_buf *xmit = &port->state->xmit;
-	int count;
-
-	if (port->x_char) {
-		UART_PUT_CHAR(port, port->x_char);
-		port->icount.tx++;
-		port->x_char = 0;
-		return;
-	}
-
-	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		apbuart_stop_tx(port);
-		return;
-	}
-
-	/* amba: fill FIFO */
-	count = port->fifosize >> 1;
-	do {
-		UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
-		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
-		port->icount.tx++;
-		if (uart_circ_empty(xmit))
-			break;
-	} while (--count > 0);
-
-	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-		uart_write_wakeup(port);
+	u8 ch;
 
-	if (uart_circ_empty(xmit))
-		apbuart_stop_tx(port);
+	uart_port_tx_limited(port, ch, port->fifosize >> 1,
+		true,
+		UART_PUT_CHAR(port, ch),
+		({}));
 }
 
 static irqreturn_t apbuart_int(int irq, void *dev_id)