diff mbox series

[v4,12/14] serial: liteuart: add IRQ support for the RX path

Message ID 20221116144908.234154-13-gsomlo@gmail.com
State New
Headers
Series serial: liteuart: add IRQ support |

Commit Message

Gabriel L. Somlo Nov. 16, 2022, 2:49 p.m. UTC 
  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>
---

Changes from v3:
  - add shadow irq register to support polling mode and avoid reading
    hardware mmio irq register to learn which irq flags are enabled
    - this also simplifies both liteuart_interrupt() and liteuart_startup()

 drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
 1 file changed, 69 insertions(+), 7 deletions(-)

Comments

Ilpo Järvinen Nov. 18, 2022, 1:58 p.m. UTC | #1 
On Wed, 16 Nov 2022, Gabriel Somlo wrote:

> 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>
> ---
> 
> Changes from v3:
>   - add shadow irq register to support polling mode and avoid reading
>     hardware mmio irq register to learn which irq flags are enabled
>     - this also simplifies both liteuart_interrupt() and liteuart_startup()
> 
>  drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
>  1 file changed, 69 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 8a6e176be08e..fad778578986 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -7,6 +7,7 @@
>  
>  #include <linux/bits.h>
>  #include <linux/console.h>
> +#include <linux/interrupt.h>
>  #include <linux/litex.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> @@ -46,6 +47,7 @@ struct liteuart_port {
>  	struct uart_port port;
>  	struct timer_list timer;
>  	u32 id;
> +	u8 irq_reg;
>  };
>  
>  #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
> @@ -76,6 +78,19 @@ static void liteuart_putchar(struct uart_port *port, unsigned char ch)
>  	litex_write8(port->membase + OFF_RXTX, ch);
>  }
>  
> +static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
> +{
> +	struct liteuart_port *uart = to_liteuart_port(port);
> +
> +	if (set)
> +		uart->irq_reg |= mask;
> +	else
> +		uart->irq_reg &= ~mask;
> +
> +	if (port->irq)
> +		litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
> +}
> +
>  static void liteuart_stop_tx(struct uart_port *port)
>  {
>  }
> @@ -129,13 +144,27 @@ 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 liteuart_port *uart = data;
> +	struct uart_port *port = &uart->port;
> +	u8 isr;
> +
> +	spin_lock(&port->lock);
> +	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> +	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));
>  }
>  
> @@ -161,19 +190,45 @@ 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);
> +	unsigned long flags;
> +	int ret;
>  
> -	/* 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) {
> +			pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
> +				port->line, port->irq);

dev_err() seems more appropriate here.

> +			port->irq = 0;
> +		}
> +	}
>  
> -	/* prepare timer for polling */
> -	timer_setup(&uart->timer, liteuart_timer, 0);
> -	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> +	spin_lock_irqsave(&port->lock, flags);
> +	/* only enabling rx irqs during startup */
> +	liteuart_update_irq_reg(port, true, EV_RX);
> +	spin_unlock_irqrestore(&port->lock, flags);
> +
> +	if (!port->irq) {
> +		timer_setup(&uart->timer, liteuart_timer, 0);
> +		mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> +	}
>  
>  	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);
> +	liteuart_update_irq_reg(port, false, EV_RX | EV_TX);
> +	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,
> @@ -262,6 +317,13 @@ static int liteuart_probe(struct platform_device *pdev)
>  		goto err_erase_id;
>  	}
>  
> +	/* get irq */

This comment is unnecessary.

Other than that,

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Gabriel L. Somlo Nov. 18, 2022, 2:26 p.m. UTC | #2 
On Fri, Nov 18, 2022 at 03:58:47PM +0200, Ilpo Järvinen wrote:
> On Wed, 16 Nov 2022, Gabriel Somlo wrote:
> 
> > 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>
> > ---
> > 
> > Changes from v3:
> >   - add shadow irq register to support polling mode and avoid reading
> >     hardware mmio irq register to learn which irq flags are enabled
> >     - this also simplifies both liteuart_interrupt() and liteuart_startup()
> > 
> >  drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
> >  1 file changed, 69 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> > index 8a6e176be08e..fad778578986 100644
> > --- a/drivers/tty/serial/liteuart.c
> > +++ b/drivers/tty/serial/liteuart.c
> > @@ -7,6 +7,7 @@
> >  
> >  #include <linux/bits.h>
> >  #include <linux/console.h>
> > +#include <linux/interrupt.h>
> >  #include <linux/litex.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> > @@ -46,6 +47,7 @@ struct liteuart_port {
> >  	struct uart_port port;
> >  	struct timer_list timer;
> >  	u32 id;
> > +	u8 irq_reg;
> >  };
> >  
> >  #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
> > @@ -76,6 +78,19 @@ static void liteuart_putchar(struct uart_port *port, unsigned char ch)
> >  	litex_write8(port->membase + OFF_RXTX, ch);
> >  }
> >  
> > +static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
> > +{
> > +	struct liteuart_port *uart = to_liteuart_port(port);
> > +
> > +	if (set)
> > +		uart->irq_reg |= mask;
> > +	else
> > +		uart->irq_reg &= ~mask;
> > +
> > +	if (port->irq)
> > +		litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
> > +}
> > +
> >  static void liteuart_stop_tx(struct uart_port *port)
> >  {
> >  }
> > @@ -129,13 +144,27 @@ 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 liteuart_port *uart = data;
> > +	struct uart_port *port = &uart->port;
> > +	u8 isr;
> > +
> > +	spin_lock(&port->lock);
> > +	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> > +	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));
> >  }
> >  
> > @@ -161,19 +190,45 @@ 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);
> > +	unsigned long flags;
> > +	int ret;
> >  
> > -	/* 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) {
> > +			pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
> > +				port->line, port->irq);
> 
> dev_err() seems more appropriate here.

Makes sense, good thing `struct uart_port` has a `dev` field :)
I've made the change, and lined it up for the upcoming v5 of the
series.
 
> > +			port->irq = 0;
> > +		}
> > +	}
> >  
> > -	/* prepare timer for polling */
> > -	timer_setup(&uart->timer, liteuart_timer, 0);
> > -	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> > +	spin_lock_irqsave(&port->lock, flags);
> > +	/* only enabling rx irqs during startup */
> > +	liteuart_update_irq_reg(port, true, EV_RX);
> > +	spin_unlock_irqrestore(&port->lock, flags);
> > +
> > +	if (!port->irq) {
> > +		timer_setup(&uart->timer, liteuart_timer, 0);
> > +		mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> > +	}
> >  
> >  	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);
> > +	liteuart_update_irq_reg(port, false, EV_RX | EV_TX);
> > +	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,
> > @@ -262,6 +317,13 @@ static int liteuart_probe(struct platform_device *pdev)
> >  		goto err_erase_id;
> >  	}
> >  
> > +	/* get irq */
> 
> This comment is unnecessary.

Removed in v5.

> Other than that,
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Thanks much, I'll send out v5 a bit later today.

--Gabriel

> -- 
>  i.
> 
> 
> > +	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;
> >
Ilpo Järvinen Nov. 18, 2022, 2:30 p.m. UTC | #3 
On Fri, 18 Nov 2022, Gabriel L. Somlo wrote:

> On Fri, Nov 18, 2022 at 03:58:47PM +0200, Ilpo Järvinen wrote:
> > On Wed, 16 Nov 2022, Gabriel Somlo wrote:
> > 
> > > 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>
> > > ---
> > > 
> > > Changes from v3:
> > >   - add shadow irq register to support polling mode and avoid reading
> > >     hardware mmio irq register to learn which irq flags are enabled
> > >     - this also simplifies both liteuart_interrupt() and liteuart_startup()
> > > 
> > >  drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
> > >  1 file changed, 69 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> > > index 8a6e176be08e..fad778578986 100644
> > > --- a/drivers/tty/serial/liteuart.c
> > > +++ b/drivers/tty/serial/liteuart.c
> > > @@ -7,6 +7,7 @@
> > >  
> > >  #include <linux/bits.h>
> > >  #include <linux/console.h>
> > > +#include <linux/interrupt.h>
> > >  #include <linux/litex.h>
> > >  #include <linux/module.h>
> > >  #include <linux/of.h>
> > > @@ -46,6 +47,7 @@ struct liteuart_port {
> > >  	struct uart_port port;
> > >  	struct timer_list timer;
> > >  	u32 id;
> > > +	u8 irq_reg;
> > >  };
> > >  
> > >  #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
> > > @@ -76,6 +78,19 @@ static void liteuart_putchar(struct uart_port *port, unsigned char ch)
> > >  	litex_write8(port->membase + OFF_RXTX, ch);
> > >  }
> > >  
> > > +static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
> > > +{
> > > +	struct liteuart_port *uart = to_liteuart_port(port);
> > > +
> > > +	if (set)
> > > +		uart->irq_reg |= mask;
> > > +	else
> > > +		uart->irq_reg &= ~mask;
> > > +
> > > +	if (port->irq)
> > > +		litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
> > > +}
> > > +
> > >  static void liteuart_stop_tx(struct uart_port *port)
> > >  {
> > >  }
> > > @@ -129,13 +144,27 @@ 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 liteuart_port *uart = data;
> > > +	struct uart_port *port = &uart->port;
> > > +	u8 isr;
> > > +
> > > +	spin_lock(&port->lock);
> > > +	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> > > +	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));
> > >  }
> > >  
> > > @@ -161,19 +190,45 @@ 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);
> > > +	unsigned long flags;
> > > +	int ret;
> > >  
> > > -	/* 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) {
> > > +			pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
> > > +				port->line, port->irq);
> > 
> > dev_err() seems more appropriate here.
> 
> Makes sense, good thing `struct uart_port` has a `dev` field :)
> I've made the change, and lined it up for the upcoming v5 of the
> series.

Also that pr_fmt() should be dropped (in case you didn't already). It was 
in my mind ealier but should have stated it explicitly.
Gabriel L. Somlo Nov. 18, 2022, 2:36 p.m. UTC | #4 
On Fri, Nov 18, 2022 at 04:30:15PM +0200, Ilpo Järvinen wrote:
> On Fri, 18 Nov 2022, Gabriel L. Somlo wrote:
> 
> > On Fri, Nov 18, 2022 at 03:58:47PM +0200, Ilpo Järvinen wrote:
> > > On Wed, 16 Nov 2022, Gabriel Somlo wrote:
> > > 
> > > > 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>
> > > > ---
> > > > 
> > > > Changes from v3:
> > > >   - add shadow irq register to support polling mode and avoid reading
> > > >     hardware mmio irq register to learn which irq flags are enabled
> > > >     - this also simplifies both liteuart_interrupt() and liteuart_startup()
> > > > 
> > > >  drivers/tty/serial/liteuart.c | 76 +++++++++++++++++++++++++++++++----
> > > >  1 file changed, 69 insertions(+), 7 deletions(-)
> > > > 
> > > > diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> > > > index 8a6e176be08e..fad778578986 100644
> > > > --- a/drivers/tty/serial/liteuart.c
> > > > +++ b/drivers/tty/serial/liteuart.c
> > > > @@ -7,6 +7,7 @@
> > > >  
> > > >  #include <linux/bits.h>
> > > >  #include <linux/console.h>
> > > > +#include <linux/interrupt.h>
> > > >  #include <linux/litex.h>
> > > >  #include <linux/module.h>
> > > >  #include <linux/of.h>
> > > > @@ -46,6 +47,7 @@ struct liteuart_port {
> > > >  	struct uart_port port;
> > > >  	struct timer_list timer;
> > > >  	u32 id;
> > > > +	u8 irq_reg;
> > > >  };
> > > >  
> > > >  #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
> > > > @@ -76,6 +78,19 @@ static void liteuart_putchar(struct uart_port *port, unsigned char ch)
> > > >  	litex_write8(port->membase + OFF_RXTX, ch);
> > > >  }
> > > >  
> > > > +static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
> > > > +{
> > > > +	struct liteuart_port *uart = to_liteuart_port(port);
> > > > +
> > > > +	if (set)
> > > > +		uart->irq_reg |= mask;
> > > > +	else
> > > > +		uart->irq_reg &= ~mask;
> > > > +
> > > > +	if (port->irq)
> > > > +		litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
> > > > +}
> > > > +
> > > >  static void liteuart_stop_tx(struct uart_port *port)
> > > >  {
> > > >  }
> > > > @@ -129,13 +144,27 @@ 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 liteuart_port *uart = data;
> > > > +	struct uart_port *port = &uart->port;
> > > > +	u8 isr;
> > > > +
> > > > +	spin_lock(&port->lock);
> > > > +	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
> > > > +	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));
> > > >  }
> > > >  
> > > > @@ -161,19 +190,45 @@ 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);
> > > > +	unsigned long flags;
> > > > +	int ret;
> > > >  
> > > > -	/* 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) {
> > > > +			pr_err(pr_fmt("line %d irq %d failed: using polling\n"),
> > > > +				port->line, port->irq);
> > > 
> > > dev_err() seems more appropriate here.
> > 
> > Makes sense, good thing `struct uart_port` has a `dev` field :)
> > I've made the change, and lined it up for the upcoming v5 of the
> > series.
> 
> Also that pr_fmt() should be dropped (in case you didn't already). It was 
> in my mind ealier but should have stated it explicitly.

Understood. I've used dev_err() before, it just slipped my mind to
check for the availability of a `dev` field in `struct uart_port`...  :)

Thanks again for the review!

Best,
--Gabriel
diff mbox series

Patch

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 8a6e176be08e..fad778578986 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -7,6 +7,7 @@ 
 
 #include <linux/bits.h>
 #include <linux/console.h>
+#include <linux/interrupt.h>
 #include <linux/litex.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -46,6 +47,7 @@  struct liteuart_port {
 	struct uart_port port;
 	struct timer_list timer;
 	u32 id;
+	u8 irq_reg;
 };
 
 #define to_liteuart_port(port)	container_of(port, struct liteuart_port, port)
@@ -76,6 +78,19 @@  static void liteuart_putchar(struct uart_port *port, unsigned char ch)
 	litex_write8(port->membase + OFF_RXTX, ch);
 }
 
+static void liteuart_update_irq_reg(struct uart_port *port, bool set, u8 mask)
+{
+	struct liteuart_port *uart = to_liteuart_port(port);
+
+	if (set)
+		uart->irq_reg |= mask;
+	else
+		uart->irq_reg &= ~mask;
+
+	if (port->irq)
+		litex_write8(port->membase + OFF_EV_ENABLE, uart->irq_reg);
+}
+
 static void liteuart_stop_tx(struct uart_port *port)
 {
 }
@@ -129,13 +144,27 @@  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 liteuart_port *uart = data;
+	struct uart_port *port = &uart->port;
+	u8 isr;
+
+	spin_lock(&port->lock);
+	isr = litex_read8(port->membase + OFF_EV_PENDING) & uart->irq_reg;
+	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));
 }
 
@@ -161,19 +190,45 @@  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);
+	unsigned long flags;
+	int ret;
 
-	/* 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) {
+			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));
+	spin_lock_irqsave(&port->lock, flags);
+	/* only enabling rx irqs during startup */
+	liteuart_update_irq_reg(port, true, EV_RX);
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	if (!port->irq) {
+		timer_setup(&uart->timer, liteuart_timer, 0);
+		mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
+	}
 
 	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);
+	liteuart_update_irq_reg(port, false, EV_RX | EV_TX);
+	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,
@@ -262,6 +317,13 @@  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;