2022-11-16 14:57:31

by Gabriel L. Somlo

Subject: [PATCH v4 13/14] serial: liteuart: add IRQ support for the TX path

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

Signed-off-by: Gabriel Somlo <[email protected]>
---

Changes from v3:
- remove superfluous curly braces from liteuart_interrupt()
- simplified [start|stop]_tx() by using shadow irq register from
patch 12/14
- simplified liteuart_tx_chars() by rebasing on top of tty-next tree

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 fad778578986..977fc4349b47 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

2022-11-18 14:36:53

by Ilpo Järvinen

Subject: Re: [PATCH v4 13/14] serial: liteuart: add IRQ support for the TX path

On Wed, 16 Nov 2022, 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 <[email protected]>
> ---
>
> Changes from v3:
> - remove superfluous curly braces from liteuart_interrupt()
> - simplified [start|stop]_tx() by using shadow irq register from
> patch 12/14
> - simplified liteuart_tx_chars() by rebasing on top of tty-next tree
>
> 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 fad778578986..977fc4349b47 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);

Looks very clean now with uart_port_tx(), thanks.

Reviewed-by: Ilpo J?rvinen <[email protected]>

--
i.