linux-kernel - Re: [PATCH v3] tty/serial: atmel: fix out of range clock divider handling

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Message-ID: <035748de-1265-b2ba-9832-898782bcccf3@gmail.com>
Date:   Mon, 16 Dec 2019 11:03:27 +0100
From:   Richard Genoud <richard.genoud@...il.com>
To:     David Engraf <david.engraf@...go.com>, gregkh@...uxfoundation.org,
        jslaby@...e.com, nicolas.ferre@...rochip.com,
        alexandre.belloni@...tlin.com, ludovic.desroches@...rochip.com
Cc:     linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tty/serial: atmel: fix out of range clock divider
 handling

Le 16/12/2019 à 09:54, David Engraf a écrit :
> Use MCK_DIV8 when the clock divider is > 65535. Unfortunately the mode
> register was already written thus the clock selection is ignored.
> 
> Fix by doing the baud rate calulation before setting the mode.
> 
> Fixes: 5bf5635ac170 ("tty/serial: atmel: add fractional baud rate support")
> Signed-off-by: David Engraf <david.engraf@...go.com>

Acked-by: Richard Genoud <richard.genoud@...il.com>


> ---
> Changes since v1: 
>  - moves set baud rate block before setting the mode register because
>    ATMEL_US_RTSDIS and ATMEL_US_RTSEN depend on ATMEL_US_MR.mode
> 
> ---
>  drivers/tty/serial/atmel_serial.c | 43 ++++++++++++++++---------------
>  1 file changed, 22 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index a8dc8af83f39..1ba9bc667e13 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -2270,27 +2270,6 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
>  		mode |= ATMEL_US_USMODE_NORMAL;
>  	}
>  
> -	/* set the mode, clock divisor, parity, stop bits and data size */
> -	atmel_uart_writel(port, ATMEL_US_MR, mode);
> -
> -	/*
> -	 * when switching the mode, set the RTS line state according to the
> -	 * new mode, otherwise keep the former state
> -	 */
> -	if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) {
> -		unsigned int rts_state;
> -
> -		if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
> -			/* let the hardware control the RTS line */
> -			rts_state = ATMEL_US_RTSDIS;
> -		} else {
> -			/* force RTS line to low level */
> -			rts_state = ATMEL_US_RTSEN;
> -		}
> -
> -		atmel_uart_writel(port, ATMEL_US_CR, rts_state);
> -	}
> -
>  	/*
>  	 * Set the baud rate:
>  	 * Fractional baudrate allows to setup output frequency more
> @@ -2317,6 +2296,28 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
>  
>  	if (!(port->iso7816.flags & SER_ISO7816_ENABLED))
>  		atmel_uart_writel(port, ATMEL_US_BRGR, quot);
> +
> +	/* set the mode, clock divisor, parity, stop bits and data size */
> +	atmel_uart_writel(port, ATMEL_US_MR, mode);
> +
> +	/*
> +	 * when switching the mode, set the RTS line state according to the
> +	 * new mode, otherwise keep the former state
> +	 */
> +	if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) {
> +		unsigned int rts_state;
> +
> +		if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
> +			/* let the hardware control the RTS line */
> +			rts_state = ATMEL_US_RTSDIS;
> +		} else {
> +			/* force RTS line to low level */
> +			rts_state = ATMEL_US_RTSEN;
> +		}
> +
> +		atmel_uart_writel(port, ATMEL_US_CR, rts_state);
> +	}
> +
>  	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
>  	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
>  	atmel_port->tx_stopped = false;
> 

Thanks !