linux-kernel - Re: [PATCH] atmel serial reduce trasmitting window & code style patch

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Date:	Tue, 8 Apr 2008 10:32:31 +0200
From:	Marc Pignat <marc.pignat@...s.ch>
To:	Michael Trimarchi <trimarchimichael@...oo.it>
Cc:	linux-kernel@...r.kernel.org,
	Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: Re: [PATCH] atmel serial reduce trasmitting window & code style patch

Hi all!

I just inlined your second patch for commenting.

On Thursday 03 April 2008, Michael Trimarchi wrote:
> Hi,
...
> http://it.docs.yahoo.com/mail/overview/index.html

> diff --git a/drivers/serial/atmel_serial.c b/drivers/serial/atmel_serial.c
> index 9f58eb3..511a0cc 100644
> --- a/drivers/serial/atmel_serial.c
> +++ b/drivers/serial/atmel_serial.c
> @@ -123,6 +123,7 @@ struct atmel_uart_char {
>  };
>  
>  #define ATMEL_SERIAL_RINGSIZE	1024
> +#define ATMEL_SERIAL_TXSIZE	32
>  
>  /*
>   * We wrap our port structure around the generic uart_port.
> @@ -426,6 +427,7 @@ static void atmel_rx_chars(struct uart_port *port)
>  static void atmel_tx_chars(struct uart_port *port)
>  {
>  	struct circ_buf *xmit = &port->info->xmit;
> +	int count = 0;
 
>  	if (port->x_char && UART_GET_CSR(port) & ATMEL_US_TXRDY) {
>  		UART_PUT_CHAR(port, port->x_char);
> @@ -435,10 +437,12 @@ static void atmel_tx_chars(struct uart_port *port)
>  	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
>  		return;
>  
> -	while (UART_GET_CSR(port) & ATMEL_US_TXRDY) {
> +	while (UART_GET_CSR(port) & ATMEL_US_TXRDY &&
> +	       count < ATMEL_SERIAL_TXSIZE) {
>  		UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
>  		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>  		port->icount.tx++;
> +		count++;
>  		if (uart_circ_empty(xmit))
>  			break;
>  	}
For me this loop will never run more than 2-3 times.
The CPU is much faster than the serial transmitter, so after 2 loops
UART_GET_CSR(port) & ATMEL_US_TXRDY will be false and the loop will exit.

If your patch does something, I can't understand how!

Best regards

Marc
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