diff mbox series

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

Message ID 20221118145512.509950-14-gsomlo@gmail.com
State New
Headers
Series serial: liteuart: add IRQ support |

Commit Message

Gabriel L. Somlo Nov. 18, 2022, 2:55 p.m. UTC 
  Switch the TX path to IRQ-driven operation, while maintaining support
for polling mode via the poll timer.

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

Comments

Jiri Slaby Nov. 21, 2022, 8:58 a.m. UTC | #1 
On 18. 11. 22, 15:55, Gabriel Somlo wrote:
> Switch the TX path to IRQ-driven operation, while maintaining support
> for polling mode via the poll timer.
> 
> Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
...
> @@ -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);

Wait, how do you ensure the OFF_EV_PENDING reg contains EV_RX and/or 
EV_TX in the polling mode?

thanks,
Gabriel L. Somlo Nov. 21, 2022, 2:07 p.m. UTC | #2 
On Mon, Nov 21, 2022 at 09:58:41AM +0100, Jiri Slaby wrote:
> On 18. 11. 22, 15:55, Gabriel Somlo wrote:
> > Switch the TX path to IRQ-driven operation, while maintaining support
> > for polling mode via the poll timer.
> > 
> > Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
> > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> ...
> > @@ -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);
> 
> Wait, how do you ensure the OFF_EV_PENDING reg contains EV_RX and/or EV_TX
> in the polling mode?

The hardware (well, *gateware*) is coded to populate the EV_PENDING
register regardless of whether IRQs are enabled via the EV_ENABLE
register (or indeed, whether IRQs are even "wired into" the design at
all). See

https://github.com/enjoy-digital/litex/blob/master/litex/soc/cores/uart.py
and
https://github.com/enjoy-digital/litex/blob/master/litex/soc/interconnect/csr_eventmanager.py

for a starting point on why it's OK to just assume that...

Thanks,
--Gabriel
diff mbox series

Patch

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);