[PATCH v3 12/14] serial: liteuart: add IRQ support for the RX path

Gabriel Somlo
2022-11-12T21:22:30Z

Add support for IRQ-driven RX. Support for the TX path will be added
in a separate commit.

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
---
drivers/tty/serial/liteuart.c | 61 +++++++++++++++++++++++++++++++----
1 file changed, 54 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index cf1ce597b45e..e30adb30277f 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -6,6 +6,7 @@
*/

#include <linux/console.h>
+#include <linux/interrupt.h>
#include <linux/litex.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -130,13 +131,29 @@ static void liteuart_rx_chars(struct uart_port *port)
tty_flip_buffer_push(&port->state->port);
}

+static irqreturn_t liteuart_interrupt(int irq, void *data)
+{
+ struct liteuart_port *uart = data;
+ struct uart_port *port = &uart->port;
+ u8 isr = litex_read8(port->membase + OFF_EV_PENDING);
+
+ /* for now, only rx path triggers interrupts */
+ isr &= EV_RX;
+
+ spin_lock(&port->lock);
+ if (isr & EV_RX)
+ liteuart_rx_chars(port);
+ spin_unlock(&port->lock);
+
+ return IRQ_RETVAL(isr);
+}
+
static void liteuart_timer(struct timer_list *t)
{
struct liteuart_port *uart = from_timer(uart, t, timer);
struct uart_port *port = &uart->port;

- liteuart_rx_chars(port);
-
+ liteuart_interrupt(0, port);
mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
}

@@ -162,19 +179,42 @@ static unsigned int liteuart_get_mctrl(struct uart_port *port)
static int liteuart_startup(struct uart_port *port)
{
struct liteuart_port *uart = to_liteuart_port(port);
+ int ret;
+ u8 irq_mask = 0;

- /* disable events */
- litex_write8(port->membase + OFF_EV_ENABLE, 0);
+ if (port->irq) {
+ ret = request_irq(port->irq, liteuart_interrupt, 0,
+ KBUILD_MODNAME, uart);
+ if (ret == 0) {
+ /* only enable rx interrupts at this time */
+ irq_mask = EV_RX;
+ } else {
+ pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
+ port->line, port->irq);
+ port->irq = 0;
+ }
+ }

- /* prepare timer for polling */
- timer_setup(&uart->timer, liteuart_timer, 0);
- mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+ if (!port->irq) {
+ timer_setup(&uart->timer, liteuart_timer, 0);
+ mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+ }
+
+ litex_write8(port->membase + OFF_EV_ENABLE, irq_mask);

return 0;
}

static void liteuart_shutdown(struct uart_port *port)
{
+ struct liteuart_port *uart = to_liteuart_port(port);
+
+ litex_write8(port->membase + OFF_EV_ENABLE, 0);
+
+ if (port->irq)
+ free_irq(port->irq, port);
+ else
+ del_timer_sync(&uart->timer);
}

static void liteuart_set_termios(struct uart_port *port, struct ktermios *new,
@@ -263,6 +303,13 @@ static int liteuart_probe(struct platform_device *pdev)
goto err_erase_id;
}

+ /* get irq */
+ ret = platform_get_irq_optional(pdev, 0);
+ if (ret < 0 && ret != -ENXIO)
+ return ret;
+ if (ret > 0)
+ port->irq = ret;
+
/* values not from device tree */
port->dev = &pdev->dev;
port->iotype = UPIO_MEM;
--
2.37.3