[PATCH v5 13/14] serial: liteuart: add IRQ support for the TX path

From: Gabriel Somlo
Date: Fri Nov 18 2022 - 09:57:16 EST


Switch the TX path to IRQ-driven operation, while maintaining support
for polling mode via the poll timer.

Signed-off-by: Gabriel Somlo <gsomlo@xxxxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/liteuart.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 678c37c952cf..850125870efb 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -93,27 +93,12 @@ static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)

static void liteuart_stop_tx(struct uart_port *port)
{
+ liteuart_update_irq_reg(port, false, EV_TX);
}

static void liteuart_start_tx(struct uart_port *port)
{
- struct circ_buf *xmit = &port->state->xmit;
- unsigned char ch;
-
- if (unlikely(port->x_char)) {
- litex_write8(port->membase + OFF_RXTX, port->x_char);
- port->icount.tx++;
- port->x_char = 0;
- } else if (!uart_circ_empty(xmit)) {
- while (xmit->head != xmit->tail) {
- ch = xmit->buf[xmit->tail];
- uart_xmit_advance(port, 1);
- liteuart_putchar(port, ch);
- }
- }
-
- if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
- uart_write_wakeup(port);
+ liteuart_update_irq_reg(port, true, EV_TX);
}

static void liteuart_stop_rx(struct uart_port *port)
@@ -144,6 +129,15 @@ static void liteuart_rx_chars(struct uart_port *port)
tty_flip_buffer_push(&port->state->port);
}

+static void liteuart_tx_chars(struct uart_port *port)
+{
+ u8 ch;
+
+ uart_port_tx(port, ch,
+ !litex_read8(port->membase + OFF_TXFULL),
+ litex_write8(port->membase + OFF_RXTX, ch));
+}
+
static irqreturn_t liteuart_interrupt(int irq, void *data)
{
struct liteuart_port *uart = data;
@@ -154,6 +148,8 @@ static irqreturn_t liteuart_interrupt(int irq, void *data)
isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
if (isr & EV_RX)
liteuart_rx_chars(port);
+ if (isr & EV_TX)
+ liteuart_tx_chars(port);
spin_unlock(&port->lock);

return IRQ_RETVAL(isr);
--
2.38.1