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Subject[PATCH v1 3/3] serial: liteuart: add IRQ support
Date
Add support for IRQ-driven RX. The TX path remains "polling" based,
which is fine since TX is synchronous.

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
---
drivers/tty/serial/liteuart.c | 65 +++++++++++++++++++++++++++++++----
1 file changed, 58 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 90a29ed79bff..47ce3ecc50f2 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>
@@ -90,13 +91,27 @@ 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 uart_port *port = data;
+ unsigned int isr;
+
+ isr = litex_read32(port->membase + OFF_EV_PENDING);
+
+ 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));
}

@@ -165,19 +180,48 @@ static void liteuart_stop_rx(struct uart_port *port)
static int liteuart_startup(struct uart_port *port)
{
struct liteuart_port *uart = to_liteuart_port(port);
+ unsigned long flags;
+ 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,
+ DRV_NAME, port);
+ if (ret == 0) {
+ /* we only need interrupts on the rx path! */
+ irq_mask = EV_RX;
+ } else {
+ pr_err(DRV_NAME ": can't attach LiteUART %d irq=%d; "
+ "switching to 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));
+ }
+
+ spin_lock_irqsave(&port->lock, flags);
+ litex_write8(port->membase + OFF_EV_ENABLE, irq_mask);
+ spin_unlock_irqrestore(&port->lock, flags);

return 0;
}

static void liteuart_shutdown(struct uart_port *port)
{
+ struct liteuart_port *uart = to_liteuart_port(port);
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->lock, flags);
+ litex_write8(port->membase + OFF_EV_ENABLE, 0);
+ spin_unlock_irqrestore(&port->lock, flags);
+
+ 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,
@@ -266,6 +310,13 @@ 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
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