target/linux/ar71xx/patches-3.3/211-ar933x_uart-improve-serial-clock-calculation.patch

   1 --- a/drivers/tty/serial/ar933x_uart.c
   2 +++ b/drivers/tty/serial/ar933x_uart.c
   3 @@ -25,11 +25,19 @@
   4  #include <linux/io.h>
   5  #include <linux/irq.h>
   6
   7 +#include <asm/div64.h>
   8 +
   9  #include <asm/mach-ath79/ar933x_uart.h>
  10  #include <asm/mach-ath79/ar933x_uart_platform.h>
  11
  12  #define DRIVER_NAME "ar933x-uart"
  13
  14 +#define AR933X_UART_MAX_SCALE  0xff
  15 +#define AR933X_UART_MAX_STEP   0xffff
  16 +
  17 +#define AR933X_UART_MIN_BAUD   300
  18 +#define AR933X_UART_MAX_BAUD   3000000
  19 +
  20  #define AR933X_DUMMY_STATUS_RD 0x01
  21
  22  static struct uart_driver ar933x_uart_driver;
  23 @@ -37,6 +45,8 @@ static struct uart_driver ar933x_uart_dr
  24  struct ar933x_uart_port {
  25         struct uart_port        port;
  26         unsigned int            ier;    /* shadow Interrupt Enable Register */
  27 +       unsigned int            min_baud;
  28 +       unsigned int            max_baud;
  29  };
  30
  31  static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
  32 @@ -162,6 +172,57 @@ static void ar933x_uart_enable_ms(struct
  33  {
  34  }
  35
  36 +/*
  37 + * baudrate = (clk / (scale + 1)) * (step * (1 / 2^17))
  38 + */
  39 +static unsigned long ar933x_uart_get_baud(unsigned int clk,
  40 +                                         unsigned int scale,
  41 +                                         unsigned int step)
  42 +{
  43 +       u64 t;
  44 +       u32 div;
  45 +
  46 +       div = (2 << 16) * (scale + 1);
  47 +       t = clk;
  48 +       t *= step;
  49 +       t += (div / 2);
  50 +       do_div(t, div);
  51 +
  52 +       return t;
  53 +}
  54 +
  55 +static void ar933x_uart_get_scale_step(unsigned int clk,
  56 +                                      unsigned int baud,
  57 +                                      unsigned int *scale,
  58 +                                      unsigned int *step)
  59 +{
  60 +       unsigned int tscale;
  61 +       long min_diff;
  62 +
  63 +       *scale = 0;
  64 +       *step = 0;
  65 +
  66 +       min_diff = baud;
  67 +       for (tscale = 0; tscale < AR933X_UART_MAX_SCALE; tscale++) {
  68 +               u64 tstep;
  69 +               int diff;
  70 +
  71 +               tstep = baud * (tscale + 1);
  72 +               tstep *= (2 << 16);
  73 +               do_div(tstep, clk);
  74 +
  75 +               if (tstep > AR933X_UART_MAX_STEP)
  76 +                       break;
  77 +
  78 +               diff = abs(ar933x_uart_get_baud(clk, tscale, tstep) - baud);
  79 +               if (diff < min_diff) {
  80 +                       min_diff = diff;
  81 +                       *scale = tscale;
  82 +                       *step = tstep;
  83 +               }
  84 +       }
  85 +}
  86 +
  87  static void ar933x_uart_set_termios(struct uart_port *port,
  88                                     struct ktermios *new,
  89                                     struct ktermios *old)
  90 @@ -169,7 +230,7 @@ static void ar933x_uart_set_termios(stru
  91         struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
  92         unsigned int cs;
  93         unsigned long flags;
  94 -       unsigned int baud, scale;
  95 +       unsigned int baud, scale, step;
  96
  97         /* Only CS8 is supported */
  98         new->c_cflag &= ~CSIZE;
  99 @@ -191,8 +252,8 @@ static void ar933x_uart_set_termios(stru
 100         /* Mark/space parity is not supported */
 101         new->c_cflag &= ~CMSPAR;
 102
 103 -       baud = uart_get_baud_rate(port, new, old, 0, port->uartclk / 16);
 104 -       scale = (port->uartclk / (16 * baud)) - 1;
 105 +       baud = uart_get_baud_rate(port, new, old, up->min_baud, up->max_baud);
 106 +       ar933x_uart_get_scale_step(port->uartclk, baud, &scale, &step);
 107
 108         /*
 109          * Ok, we're now changing the port state. Do it with
 110 @@ -200,6 +261,10 @@ static void ar933x_uart_set_termios(stru
 111          */
 112         spin_lock_irqsave(&up->port.lock, flags);
 113
 114 +       /* disable the UART */
 115 +       ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
 116 +                     AR933X_UART_CS_IF_MODE_M << AR933X_UART_CS_IF_MODE_S);
 117 +
 118         /* Update the per-port timeout. */
 119         uart_update_timeout(port, new->c_cflag, baud);
 120
 121 @@ -210,7 +275,7 @@ static void ar933x_uart_set_termios(stru
 122                 up->port.ignore_status_mask |= AR933X_DUMMY_STATUS_RD;
 123
 124         ar933x_uart_write(up, AR933X_UART_CLOCK_REG,
 125 -                         scale << AR933X_UART_CLOCK_SCALE_S | 8192);
 126 +                         scale << AR933X_UART_CLOCK_SCALE_S | step);
 127
 128         /* setup configuration register */
 129         ar933x_uart_rmw(up, AR933X_UART_CS_REG, AR933X_UART_CS_PARITY_M, cs);
 130 @@ -219,6 +284,11 @@ static void ar933x_uart_set_termios(stru
 131         ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
 132                             AR933X_UART_CS_HOST_INT_EN);
 133
 134 +       /* reenable the UART */
 135 +       ar933x_uart_rmw(up, AR933X_UART_CS_REG,
 136 +                       AR933X_UART_CS_IF_MODE_M << AR933X_UART_CS_IF_MODE_S,
 137 +                       AR933X_UART_CS_IF_MODE_DCE << AR933X_UART_CS_IF_MODE_S);
 138 +
 139         spin_unlock_irqrestore(&up->port.lock, flags);
 140
 141         if (tty_termios_baud_rate(new))
 142 @@ -401,6 +471,8 @@ static void ar933x_uart_config_port(stru
 143  static int ar933x_uart_verify_port(struct uart_port *port,
 144                                    struct serial_struct *ser)
 145  {
 146 +       struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
 147 +
 148         if (ser->type != PORT_UNKNOWN &&
 149             ser->type != PORT_AR933X)
 150                 return -EINVAL;
 151 @@ -408,7 +480,8 @@ static int ar933x_uart_verify_port(struc
 152         if (ser->irq < 0 || ser->irq >= NR_IRQS)
 153                 return -EINVAL;
 154
 155 -       if (ser->baud_base < 28800)
 156 +       if (ser->baud_base < up->min_baud ||
 157 +           ser->baud_base > up->max_baud)
 158                 return -EINVAL;
 159
 160         return 0;
 161 @@ -561,6 +634,7 @@ static int __devinit ar933x_uart_probe(s
 162         struct uart_port *port;
 163         struct resource *mem_res;
 164         struct resource *irq_res;
 165 +       unsigned int baud;
 166         int id;
 167         int ret;
 168
 169 @@ -611,6 +685,12 @@ static int __devinit ar933x_uart_probe(s
 170         port->fifosize = AR933X_UART_FIFO_SIZE;
 171         port->ops = &ar933x_uart_ops;
 172
 173 +       baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
 174 +       up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
 175 +
 176 +       baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
 177 +       up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
 178 +
 179         ar933x_uart_add_console_port(up);
 180
 181         ret = uart_add_one_port(&ar933x_uart_driver, &up->port);