linux-kernel - Re: [PATCH v2 4/4] serial: samsung: Fix UART status handling in DMA mode

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Date:	Fri, 11 Sep 2015 15:07:58 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Robert Baldyga <r.baldyga@...sung.com>, gregkh@...uxfoundation.org
Cc:	jslaby@...e.com, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, m.szyprowski@...sung.com
Subject: Re: [PATCH v2 4/4] serial: samsung: Fix UART status handling in DMA
 mode

On 10.09.2015 22:41, Robert Baldyga wrote:
> This patch fixes UART status handling in DMA mode.

I don't see any changes here. You did not respond to my comment neither.

Code looks itself good... except a locking issue but I don't know what's
the cause. It may be not related to the patchset and maybe just not all
of issues are fixed yet. Anyway I'll describe it in 3/4.

Best regards,
Krzysztof

> For this purpose we
> use s3c24xx_serial_rx_drain_fifo() instead of uart_rx_drain_fifo(), which
> does the same thing plus checks for special conditions (such as 'break').
> 
> Thanks to this we have, for example, Magic SysRq handling, which was
> missing in DMA mode so far. Since we can use UART in DMA mode as serial
> console, this is a quite important improvement.
> 
> This change additionally simplifies RX handling code, as we no longer
> need uart_rx_drain_fifo() function, so we can remove it.
> 
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
> ---
>  drivers/tty/serial/samsung.c | 30 +++---------------------------
>  1 file changed, 3 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index 1d7dd86..d72cd73 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -385,32 +385,6 @@ static void s3c24xx_uart_copy_rx_to_tty(struct s3c24xx_uart_port *ourport,
>  	}
>  }
>  
> -static int s3c24xx_serial_rx_fifocnt(struct s3c24xx_uart_port *ourport,
> -				     unsigned long ufstat);
> -
> -static void uart_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
> -{
> -	struct uart_port *port = &ourport->port;
> -	struct tty_port *tty = &port->state->port;
> -	unsigned int ch, ufstat;
> -	unsigned int count;
> -
> -	ufstat = rd_regl(port, S3C2410_UFSTAT);
> -	count = s3c24xx_serial_rx_fifocnt(ourport, ufstat);
> -
> -	if (!count)
> -		return;
> -
> -	while (count-- > 0) {
> -		ch = rd_regb(port, S3C2410_URXH);
> -
> -		ourport->port.icount.rx++;
> -		tty_insert_flip_char(tty, ch, TTY_NORMAL);
> -	}
> -
> -	tty_flip_buffer_push(tty);
> -}
> -
>  static void s3c24xx_serial_stop_rx(struct uart_port *port)
>  {
>  	struct s3c24xx_uart_port *ourport = to_ourport(port);
> @@ -573,6 +547,8 @@ static void enable_rx_pio(struct s3c24xx_uart_port *ourport)
>  	ourport->rx_mode = S3C24XX_RX_PIO;
>  }
>  
> +static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport);
> +
>  static irqreturn_t s3c24xx_serial_rx_chars_dma(void *dev_id)
>  {
>  	unsigned int utrstat, ufstat, received;
> @@ -606,7 +582,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_dma(void *dev_id)
>  		enable_rx_pio(ourport);
>  	}
>  
> -	uart_rx_drain_fifo(ourport);
> +	s3c24xx_serial_rx_drain_fifo(ourport);
>  
>  	if (tty) {
>  		tty_flip_buffer_push(t);
> 

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