diff options
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/xilinx_uartps.c | 136 |
1 files changed, 93 insertions, 43 deletions
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c index fdc739b55eb3..95e12c216984 100644 --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -156,6 +156,11 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255"); #define XUARTPS_SR_TXFULL 0x00000010 /* TX FIFO full */ #define XUARTPS_SR_RXTRIG 0x00000001 /* Rx Trigger */ +/* baud dividers min/max values */ +#define XUARTPS_BDIV_MIN 4 +#define XUARTPS_BDIV_MAX 255 +#define XUARTPS_CD_MAX 65535 + /** * struct xuartps - device data * @refclk Reference clock @@ -305,59 +310,94 @@ static irqreturn_t xuartps_isr(int irq, void *dev_id) } /** - * xuartps_set_baud_rate - Calculate and set the baud rate - * @port: Handle to the uart port structure - * @baud: Baud rate to set - * + * xuartps_calc_baud_divs - Calculate baud rate divisors + * @clk: UART module input clock + * @baud: Desired baud rate + * @rbdiv: BDIV value (return value) + * @rcd: CD value (return value) + * @div8: Value for clk_sel bit in mod (return value) * Returns baud rate, requested baud when possible, or actual baud when there - * was too much error - **/ -static unsigned int xuartps_set_baud_rate(struct uart_port *port, - unsigned int baud) + * was too much error, zero if no valid divisors are found. + * + * Formula to obtain baud rate is + * baud_tx/rx rate = clk/CD * (BDIV + 1) + * input_clk = (Uart User Defined Clock or Apb Clock) + * depends on UCLKEN in MR Reg + * clk = input_clk or input_clk/8; + * depends on CLKS in MR reg + * CD and BDIV depends on values in + * baud rate generate register + * baud rate clock divisor register + */ +static unsigned int xuartps_calc_baud_divs(unsigned int clk, unsigned int baud, + u32 *rbdiv, u32 *rcd, int *div8) { - unsigned int sel_clk; - unsigned int calc_baud = 0; - unsigned int brgr_val, brdiv_val; + u32 cd, bdiv; + unsigned int calc_baud; + unsigned int bestbaud = 0; unsigned int bauderror; + unsigned int besterror = ~0; - /* Formula to obtain baud rate is - * baud_tx/rx rate = sel_clk/CD * (BDIV + 1) - * input_clk = (Uart User Defined Clock or Apb Clock) - * depends on UCLKEN in MR Reg - * sel_clk = input_clk or input_clk/8; - * depends on CLKS in MR reg - * CD and BDIV depends on values in - * baud rate generate register - * baud rate clock divisor register - */ - sel_clk = port->uartclk; - if (xuartps_readl(XUARTPS_MR_OFFSET) & XUARTPS_MR_CLKSEL) - sel_clk = sel_clk / 8; - - /* Find the best values for baud generation */ - for (brdiv_val = 4; brdiv_val < 255; brdiv_val++) { + if (baud < clk / ((XUARTPS_BDIV_MAX + 1) * XUARTPS_CD_MAX)) { + *div8 = 1; + clk /= 8; + } else { + *div8 = 0; + } - brgr_val = sel_clk / (baud * (brdiv_val + 1)); - if (brgr_val < 2 || brgr_val > 65535) + for (bdiv = XUARTPS_BDIV_MIN; bdiv <= XUARTPS_BDIV_MAX; bdiv++) { + cd = DIV_ROUND_CLOSEST(clk, baud * (bdiv + 1)); + if (cd < 1 || cd > XUARTPS_CD_MAX) continue; - calc_baud = sel_clk / (brgr_val * (brdiv_val + 1)); + calc_baud = clk / (cd * (bdiv + 1)); if (baud > calc_baud) bauderror = baud - calc_baud; else bauderror = calc_baud - baud; - /* use the values when percent error is acceptable */ - if (((bauderror * 100) / baud) < 3) { - calc_baud = baud; - break; + if (besterror > bauderror) { + *rbdiv = bdiv; + *rcd = cd; + bestbaud = calc_baud; + besterror = bauderror; } } + /* use the values when percent error is acceptable */ + if (((besterror * 100) / baud) < 3) + bestbaud = baud; + + return bestbaud; +} - /* Set the values for the new baud rate */ - xuartps_writel(brgr_val, XUARTPS_BAUDGEN_OFFSET); - xuartps_writel(brdiv_val, XUARTPS_BAUDDIV_OFFSET); +/** + * xuartps_set_baud_rate - Calculate and set the baud rate + * @port: Handle to the uart port structure + * @baud: Baud rate to set + * Returns baud rate, requested baud when possible, or actual baud when there + * was too much error, zero if no valid divisors are found. + */ +static unsigned int xuartps_set_baud_rate(struct uart_port *port, + unsigned int baud) +{ + unsigned int calc_baud; + u32 cd, bdiv; + u32 mreg; + int div8; + + calc_baud = xuartps_calc_baud_divs(port->uartclk, baud, &bdiv, &cd, + &div8); + + /* Write new divisors to hardware */ + mreg = xuartps_readl(XUARTPS_MR_OFFSET); + if (div8) + mreg |= XUARTPS_MR_CLKSEL; + else + mreg &= ~XUARTPS_MR_CLKSEL; + xuartps_writel(mreg, XUARTPS_MR_OFFSET); + xuartps_writel(cd, XUARTPS_BAUDGEN_OFFSET); + xuartps_writel(bdiv, XUARTPS_BAUDDIV_OFFSET); return calc_baud; } @@ -495,7 +535,7 @@ static void xuartps_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) { unsigned int cval = 0; - unsigned int baud; + unsigned int baud, minbaud, maxbaud; unsigned long flags; unsigned int ctrl_reg, mode_reg; @@ -512,8 +552,14 @@ static void xuartps_set_termios(struct uart_port *port, (XUARTPS_CR_TX_DIS | XUARTPS_CR_RX_DIS), XUARTPS_CR_OFFSET); - /* Min baud rate = 6bps and Max Baud Rate is 10Mbps for 100Mhz clk */ - baud = uart_get_baud_rate(port, termios, old, 0, 10000000); + /* + * Min baud rate = 6bps and Max Baud Rate is 10Mbps for 100Mhz clk + * min and max baud should be calculated here based on port->uartclk. + * this way we get a valid baud and can safely call set_baud() + */ + minbaud = port->uartclk / ((XUARTPS_BDIV_MAX + 1) * XUARTPS_CD_MAX * 8); + maxbaud = port->uartclk / (XUARTPS_BDIV_MIN + 1); + baud = uart_get_baud_rate(port, termios, old, minbaud, maxbaud); baud = xuartps_set_baud_rate(port, baud); if (tty_termios_baud_rate(termios)) tty_termios_encode_baud_rate(termios, baud, baud); @@ -589,13 +635,17 @@ static void xuartps_set_termios(struct uart_port *port, cval |= XUARTPS_MR_PARITY_MARK; else cval |= XUARTPS_MR_PARITY_SPACE; - } else if (termios->c_cflag & PARODD) + } else { + if (termios->c_cflag & PARODD) cval |= XUARTPS_MR_PARITY_ODD; else cval |= XUARTPS_MR_PARITY_EVEN; - } else + } + } else { cval |= XUARTPS_MR_PARITY_NONE; - xuartps_writel(cval , XUARTPS_MR_OFFSET); + } + cval |= mode_reg & 1; + xuartps_writel(cval, XUARTPS_MR_OFFSET); spin_unlock_irqrestore(&port->lock, flags); } |