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 <[email protected]>
Acked-by: Nicolas Ferre <[email protected]> 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
