diff options
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/fsl_lpuart.c | 79 |
1 files changed, 72 insertions, 7 deletions
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index a0f2666d30cf..343de8c384b0 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -140,6 +140,8 @@ #define UARTBAUD_SBNS 0x00002000 #define UARTBAUD_SBR 0x00000000 #define UARTBAUD_SBR_MASK 0x1fff +#define UARTBAUD_OSR_MASK 0x1f +#define UARTBAUD_OSR_SHIFT 24 #define UARTSTAT_LBKDIF 0x80000000 #define UARTSTAT_RXEDGIF 0x40000000 @@ -1511,6 +1513,75 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios, } static void +lpuart32_serial_setbrg(struct lpuart_port *sport, unsigned int baudrate) +{ + u32 sbr, osr, baud_diff, tmp_osr, tmp_sbr, tmp_diff, tmp; + u32 clk = sport->port.uartclk; + + /* + * The idea is to use the best OSR (over-sampling rate) possible. + * Note, OSR is typically hard-set to 16 in other LPUART instantiations. + * Loop to find the best OSR value possible, one that generates minimum + * baud_diff iterate through the rest of the supported values of OSR. + * + * Calculation Formula: + * Baud Rate = baud clock / ((OSR+1) × SBR) + */ + baud_diff = baudrate; + osr = 0; + sbr = 0; + + for (tmp_osr = 4; tmp_osr <= 32; tmp_osr++) { + /* calculate the temporary sbr value */ + tmp_sbr = (clk / (baudrate * tmp_osr)); + if (tmp_sbr == 0) + tmp_sbr = 1; + + /* + * calculate the baud rate difference based on the temporary + * osr and sbr values + */ + tmp_diff = clk / (tmp_osr * tmp_sbr) - baudrate; + + /* select best values between sbr and sbr+1 */ + tmp = clk / (tmp_osr * (tmp_sbr + 1)); + if (tmp_diff > (baudrate - tmp)) { + tmp_diff = baudrate - tmp; + tmp_sbr++; + } + + if (tmp_diff <= baud_diff) { + baud_diff = tmp_diff; + osr = tmp_osr; + sbr = tmp_sbr; + + if (!baud_diff) + break; + } + } + + /* handle buadrate outside acceptable rate */ + if (baud_diff > ((baudrate / 100) * 3)) + dev_warn(sport->port.dev, + "unacceptable baud rate difference of more than 3%%\n"); + + tmp = lpuart32_read(&sport->port, UARTBAUD); + + if ((osr > 3) && (osr < 8)) + tmp |= UARTBAUD_BOTHEDGE; + + tmp &= ~(UARTBAUD_OSR_MASK << UARTBAUD_OSR_SHIFT); + tmp |= (((osr-1) & UARTBAUD_OSR_MASK) << UARTBAUD_OSR_SHIFT); + + tmp &= ~UARTBAUD_SBR_MASK; + tmp |= sbr & UARTBAUD_SBR_MASK; + + tmp &= ~(UARTBAUD_TDMAE | UARTBAUD_RDMAE); + + lpuart32_write(&sport->port, tmp, UARTBAUD); +} + +static void lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) { @@ -1519,7 +1590,6 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, unsigned long ctrl, old_ctrl, bd, modem; unsigned int baud; unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8; - unsigned int sbr; ctrl = old_ctrl = lpuart32_read(&sport->port, UARTCTRL); bd = lpuart32_read(&sport->port, UARTBAUD); @@ -1616,12 +1686,7 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, lpuart32_write(&sport->port, old_ctrl & ~(UARTCTRL_TE | UARTCTRL_RE), UARTCTRL); - sbr = sport->port.uartclk / (16 * baud); - bd &= ~UARTBAUD_SBR_MASK; - bd |= sbr & UARTBAUD_SBR_MASK; - bd |= UARTBAUD_BOTHEDGE; - bd &= ~(UARTBAUD_TDMAE | UARTBAUD_RDMAE); - lpuart32_write(&sport->port, bd, UARTBAUD); + lpuart32_serial_setbrg(sport, baud); lpuart32_write(&sport->port, modem, UARTMODIR); lpuart32_write(&sport->port, ctrl, UARTCTRL); /* restore control register */ |