diff mbox series

[v2,6/7] serial: liteuart: separate RX loop from poll timer

Message ID 20221110004450.772768-7-gsomlo@gmail.com
State New
Headers
Series serial: liteuart: add IRQ support |

Commit Message

Gabriel L. Somlo Nov. 10, 2022, 12:44 a.m. UTC 
  Move the character-receive (RX) loop to its own dedicated function,
and (for now) call that from the poll timer, liteuart_timer().

This is in preparation for adding IRQ support to the receive path.

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
---
 drivers/tty/serial/liteuart.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

Comments

Ilpo Järvinen Nov. 10, 2022, 11:01 a.m. UTC | #1 
On Wed, 9 Nov 2022, Gabriel Somlo wrote:

> Move the character-receive (RX) loop to its own dedicated function,
> and (for now) call that from the poll timer, liteuart_timer().
> 
> This is in preparation for adding IRQ support to the receive path.
> 
> Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
> ---
>  drivers/tty/serial/liteuart.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 047d5ad32e13..aa7052280197 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -67,29 +67,34 @@ static struct uart_driver liteuart_driver = {
>  #endif
>  };
>  
> -static void liteuart_timer(struct timer_list *t)
> +static void liteuart_rx_chars(struct uart_port *port)
>  {
> -	struct liteuart_port *uart = from_timer(uart, t, timer);
> -	struct uart_port *port = &uart->port;
>  	unsigned char __iomem *membase = port->membase;
> -	unsigned int flg = TTY_NORMAL;
> -	int ch;
> -	unsigned long status;
> +	unsigned int status;
> +	unsigned char ch;
>  
>  	while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
>  		ch = litex_read8(membase + OFF_RXTX);
>  		port->icount.rx++;
>  
>  		/* necessary for RXEMPTY to refresh its value */
> -		litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
> +		litex_write8(membase + OFF_EV_PENDING, EV_RX);
>  
>  		/* no overflow bits in status */
>  		if (!(uart_handle_sysrq_char(port, ch)))
> -			uart_insert_char(port, status, 0, ch, flg);
> -
> -		tty_flip_buffer_push(&port->state->port);
> +			uart_insert_char(port, status, 0, ch, TTY_NORMAL);
>  	}
>  
> +	tty_flip_buffer_push(&port->state->port);

This change is doing extra stuff besides moving rx to a dedicated 
function.

I see no reason why those other changes couldn't be put into an entirely 
separate patch. Also, please described those changes properly in the 
commit message (answer the why? question).
Gabriel L. Somlo Nov. 10, 2022, 8:29 p.m. UTC | #2 
On Thu, Nov 10, 2022 at 01:01:47PM +0200, Ilpo Järvinen wrote:
> On Wed, 9 Nov 2022, Gabriel Somlo wrote:
> 
> > Move the character-receive (RX) loop to its own dedicated function,
> > and (for now) call that from the poll timer, liteuart_timer().
> > 
> > This is in preparation for adding IRQ support to the receive path.
> > 
> > Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
> > ---
> >  drivers/tty/serial/liteuart.c | 25 +++++++++++++++----------
> >  1 file changed, 15 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> > index 047d5ad32e13..aa7052280197 100644
> > --- a/drivers/tty/serial/liteuart.c
> > +++ b/drivers/tty/serial/liteuart.c
> > @@ -67,29 +67,34 @@ static struct uart_driver liteuart_driver = {
> >  #endif
> >  };
> >  
> > -static void liteuart_timer(struct timer_list *t)
> > +static void liteuart_rx_chars(struct uart_port *port)
> >  {
> > -	struct liteuart_port *uart = from_timer(uart, t, timer);
> > -	struct uart_port *port = &uart->port;
> >  	unsigned char __iomem *membase = port->membase;
> > -	unsigned int flg = TTY_NORMAL;
> > -	int ch;
> > -	unsigned long status;
> > +	unsigned int status;
> > +	unsigned char ch;
> >  
> >  	while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
> >  		ch = litex_read8(membase + OFF_RXTX);
> >  		port->icount.rx++;
> >  
> >  		/* necessary for RXEMPTY to refresh its value */
> > -		litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
> > +		litex_write8(membase + OFF_EV_PENDING, EV_RX);
> >  
> >  		/* no overflow bits in status */
> >  		if (!(uart_handle_sysrq_char(port, ch)))
> > -			uart_insert_char(port, status, 0, ch, flg);
> > -
> > -		tty_flip_buffer_push(&port->state->port);
> > +			uart_insert_char(port, status, 0, ch, TTY_NORMAL);
> >  	}
> >  
> > +	tty_flip_buffer_push(&port->state->port);
> 
> This change is doing extra stuff besides moving rx to a dedicated 
> function.
> 
> I see no reason why those other changes couldn't be put into an entirely 
> separate patch. Also, please described those changes properly in the 
> commit message (answer the why? question).
 
You're right, calling `tty_flip_buffer_push()` as each character is
received is overkill, we only need to call it once per interrupt once
all available characters have been received.

I forgot I noticed (and fixed) that as part of the move -- I'll split
it out into its own separate patch (probably *before* moving all of rx
to a dedicated function).

Should show up in v3, once I also address all the other feedback I
received.

Thanks again for catching it!

Cheers,
-Gabriel

> -- 
>  i.
> 
> > +}
> > +
> > +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);
> > +
> >  	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
> >  }
> >  
> > 
> 
>
diff mbox series

Patch

diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
index 047d5ad32e13..aa7052280197 100644
--- a/drivers/tty/serial/liteuart.c
+++ b/drivers/tty/serial/liteuart.c
@@ -67,29 +67,34 @@  static struct uart_driver liteuart_driver = {
 #endif
 };
 
-static void liteuart_timer(struct timer_list *t)
+static void liteuart_rx_chars(struct uart_port *port)
 {
-	struct liteuart_port *uart = from_timer(uart, t, timer);
-	struct uart_port *port = &uart->port;
 	unsigned char __iomem *membase = port->membase;
-	unsigned int flg = TTY_NORMAL;
-	int ch;
-	unsigned long status;
+	unsigned int status;
+	unsigned char ch;
 
 	while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
 		ch = litex_read8(membase + OFF_RXTX);
 		port->icount.rx++;
 
 		/* necessary for RXEMPTY to refresh its value */
-		litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
+		litex_write8(membase + OFF_EV_PENDING, EV_RX);
 
 		/* no overflow bits in status */
 		if (!(uart_handle_sysrq_char(port, ch)))
-			uart_insert_char(port, status, 0, ch, flg);
-
-		tty_flip_buffer_push(&port->state->port);
+			uart_insert_char(port, status, 0, ch, TTY_NORMAL);
 	}
 
+	tty_flip_buffer_push(&port->state->port);
+}
+
+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);
+
 	mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
 }