Le 25/08/2016 à 15:47, Ludovic Desroches a écrit :
> The USART device provides a fractional baud rate generator to get a more
> accurate baud rate. It can be used only when the USART is configured in
> 'normal mode' and this feature is not available on AT91RM9200 SoC.
>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Thanks, bye,
> ---
> drivers/tty/serial/atmel_serial.c | 41 +++++++++++++++++++++++++++++++--------
> include/linux/atmel_serial.h | 1 +
> 2 files changed, 34 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 2eaa18d..1759239 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -166,6 +166,7 @@ struct atmel_uart_port {
> u32 rts_low;
> bool ms_irq_enabled;
> u32 rtor; /* address of receiver timeout register if it exists */
> + bool has_frac_baudrate;
> bool has_hw_timer;
> struct timer_list uart_timer;
>
> @@ -1745,6 +1746,11 @@ static void atmel_get_ip_name(struct uart_port *port)
> dbgu_uart = 0x44424755; /* DBGU */
> new_uart = 0x55415254; /* UART */
>
> + /*
> + * Only USART devices from at91sam9260 SOC implement fractional
> + * baudrate.
> + */
> + atmel_port->has_frac_baudrate = false;
> atmel_port->has_hw_timer = false;
>
> if (name == new_uart) {
> @@ -1753,6 +1759,7 @@ static void atmel_get_ip_name(struct uart_port *port)
> atmel_port->rtor = ATMEL_UA_RTOR;
> } else if (name == usart) {
> dev_dbg(port->dev, "Usart\n");
> + atmel_port->has_frac_baudrate = true;
> atmel_port->has_hw_timer = true;
> atmel_port->rtor = ATMEL_US_RTOR;
> } else if (name == dbgu_uart) {
> @@ -1764,6 +1771,7 @@ static void atmel_get_ip_name(struct uart_port *port)
> case 0x302:
> case 0x10213:
> dev_dbg(port->dev, "This version is usart\n");
> + atmel_port->has_frac_baudrate = true;
> atmel_port->has_hw_timer = true;
> atmel_port->rtor = ATMEL_US_RTOR;
> break;
> @@ -2025,8 +2033,9 @@ static void atmel_serial_pm(struct uart_port *port, unsigned int state,
> static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
> struct ktermios *old)
> {
> + struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> unsigned long flags;
> - unsigned int old_mode, mode, imr, quot, baud;
> + unsigned int old_mode, mode, imr, quot, baud, div, cd, fp = 0;
>
> /* save the current mode register */
> mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR);
> @@ -2036,12 +2045,6 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
> ATMEL_US_PAR | ATMEL_US_USMODE);
>
> baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
> - quot = uart_get_divisor(port, baud);
> -
> - if (quot > 65535) { /* BRGR is 16-bit, so switch to slower clock */
> - quot /= 8;
> - mode |= ATMEL_US_USCLKS_MCK_DIV8;
> - }
>
> /* byte size */
> switch (termios->c_cflag & CSIZE) {
> @@ -2160,7 +2163,29 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
> atmel_uart_writel(port, ATMEL_US_CR, rts_state);
> }
>
> - /* set the baud rate */
> + /*
> + * Set the baud rate:
> + * Fractional baudrate allows to setup output frequency more
> + * accurately. This feature is enabled only when using normal mode.
> + * baudrate = selected clock / (8 * (2 - OVER) * (CD + FP / 8))
> + * Currently, OVER is always set to 0 so we get
> + * baudrate = selected clock (16 * (CD + FP / 8))
> + */
> + if (atmel_port->has_frac_baudrate &&
> + (mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_NORMAL) {
> + div = DIV_ROUND_CLOSEST(port->uartclk, baud);
> + cd = div / 16;
> + fp = DIV_ROUND_CLOSEST(div % 16, 2);
> + } else {
> + cd = uart_get_divisor(port, baud);
> + }
> +
> + if (cd > 65535) { /* BRGR is 16-bit, so switch to slower clock */
> + cd /= 8;
> + mode |= ATMEL_US_USCLKS_MCK_DIV8;
> + }
> + quot = cd | fp << ATMEL_US_FP_OFFSET;
> +
> atmel_uart_writel(port, ATMEL_US_BRGR, quot);
> 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);
> diff --git a/include/linux/atmel_serial.h b/include/linux/atmel_serial.h
> index 5a4d664..f8e452a 100644
> --- a/include/linux/atmel_serial.h
> +++ b/include/linux/atmel_serial.h
> @@ -118,6 +118,7 @@
>
> #define ATMEL_US_BRGR 0x20 /* Baud Rate Generator Register */
> #define ATMEL_US_CD GENMASK(15, 0) /* Clock Divider */
> +#define ATMEL_US_FP_OFFSET 16 /* Fractional Part */
>
> #define ATMEL_US_RTOR 0x24 /* Receiver Time-out Register for USART */
> #define ATMEL_UA_RTOR 0x28 /* Receiver Time-out Register for UART */
>
--
Nicolas Ferre
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