ar71xx: fix serial clock calculation on AR933x

Closes #12031.

SVN-Revision: 33230

diff --git a/target/linux/ar71xx/patches-3.3/211-ar933x_uart-improve-serial-clock-calculation.patch b/target/linux/ar71xx/patches-3.3/211-ar933x_uart-improve-serial-clock-calculation.patch
new file mode 100644 (file)
index 0000000..510b75e
--- /dev/null
+++ b/target/linux/ar71xx/patches-3.3/211-ar933x_uart-improve-serial-clock-calculation.patch
@@ -0,0 +1,181 @@
+--- a/drivers/tty/serial/ar933x_uart.c
++++ b/drivers/tty/serial/ar933x_uart.c
+@@ -25,11 +25,19 @@
+ #include <linux/io.h>
+ #include <linux/irq.h>
+ 
++#include <asm/div64.h>
++
+ #include <asm/mach-ath79/ar933x_uart.h>
+ #include <asm/mach-ath79/ar933x_uart_platform.h>
+ 
+ #define DRIVER_NAME "ar933x-uart"
+ 
++#define AR933X_UART_MAX_SCALE 0xff
++#define AR933X_UART_MAX_STEP  0xffff
++
++#define AR933X_UART_MIN_BAUD  300
++#define AR933X_UART_MAX_BAUD  3000000
++
+ #define AR933X_DUMMY_STATUS_RD        0x01
+ 
+ static struct uart_driver ar933x_uart_driver;
+@@ -37,6 +45,8 @@ static struct uart_driver ar933x_uart_dr
+ struct ar933x_uart_port {
+       struct uart_port        port;
+       unsigned int            ier;    /* shadow Interrupt Enable Register */
++      unsigned int            min_baud;
++      unsigned int            max_baud;
+ };
+ 
+ static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
+@@ -162,6 +172,57 @@ static void ar933x_uart_enable_ms(struct
+ {
+ }
+ 
++/*
++ * baudrate = (clk / (scale + 1)) * (step * (1 / 2^17))
++ */
++static unsigned long ar933x_uart_get_baud(unsigned int clk,
++                                        unsigned int scale,
++                                        unsigned int step)
++{
++      u64 t;
++      u32 div;
++
++      div = (2 << 16) * (scale + 1);
++      t = clk;
++      t *= step;
++      t += (div / 2);
++      do_div(t, div);
++
++      return t;
++}
++
++static void ar933x_uart_get_scale_step(unsigned int clk,
++                                     unsigned int baud,
++                                     unsigned int *scale,
++                                     unsigned int *step)
++{
++      unsigned int tscale;
++      long min_diff;
++
++      *scale = 0;
++      *step = 0;
++
++      min_diff = baud;
++      for (tscale = 0; tscale < AR933X_UART_MAX_SCALE; tscale++) {
++              u64 tstep;
++              int diff;
++
++              tstep = baud * (tscale + 1);
++              tstep *= (2 << 16);
++              do_div(tstep, clk);
++
++              if (tstep > AR933X_UART_MAX_STEP)
++                      break;
++
++              diff = abs(ar933x_uart_get_baud(clk, tscale, tstep) - baud);
++              if (diff < min_diff) {
++                      min_diff = diff;
++                      *scale = tscale;
++                      *step = tstep;
++              }
++      }
++}
++
+ static void ar933x_uart_set_termios(struct uart_port *port,
+                                   struct ktermios *new,
+                                   struct ktermios *old)
+@@ -169,7 +230,7 @@ static void ar933x_uart_set_termios(stru
+       struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
+       unsigned int cs;
+       unsigned long flags;
+-      unsigned int baud, scale;
++      unsigned int baud, scale, step;
+ 
+       /* Only CS8 is supported */
+       new->c_cflag &= ~CSIZE;
+@@ -191,8 +252,8 @@ static void ar933x_uart_set_termios(stru
+       /* Mark/space parity is not supported */
+       new->c_cflag &= ~CMSPAR;
+ 
+-      baud = uart_get_baud_rate(port, new, old, 0, port->uartclk / 16);
+-      scale = (port->uartclk / (16 * baud)) - 1;
++      baud = uart_get_baud_rate(port, new, old, up->min_baud, up->max_baud);
++      ar933x_uart_get_scale_step(port->uartclk, baud, &scale, &step);
+ 
+       /*
+        * Ok, we're now changing the port state. Do it with
+@@ -200,6 +261,10 @@ static void ar933x_uart_set_termios(stru
+        */
+       spin_lock_irqsave(&up->port.lock, flags);
+ 
++      /* disable the UART */
++      ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
++                    AR933X_UART_CS_IF_MODE_M << AR933X_UART_CS_IF_MODE_S);
++
+       /* Update the per-port timeout. */
+       uart_update_timeout(port, new->c_cflag, baud);
+ 
+@@ -210,7 +275,7 @@ static void ar933x_uart_set_termios(stru
+               up->port.ignore_status_mask |= AR933X_DUMMY_STATUS_RD;
+ 
+       ar933x_uart_write(up, AR933X_UART_CLOCK_REG,
+-                        scale << AR933X_UART_CLOCK_SCALE_S | 8192);
++                        scale << AR933X_UART_CLOCK_SCALE_S | step);
+ 
+       /* setup configuration register */
+       ar933x_uart_rmw(up, AR933X_UART_CS_REG, AR933X_UART_CS_PARITY_M, cs);
+@@ -219,6 +284,11 @@ static void ar933x_uart_set_termios(stru
+       ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
+                           AR933X_UART_CS_HOST_INT_EN);
+ 
++      /* reenable the UART */
++      ar933x_uart_rmw(up, AR933X_UART_CS_REG,
++                      AR933X_UART_CS_IF_MODE_M << AR933X_UART_CS_IF_MODE_S,
++                      AR933X_UART_CS_IF_MODE_DCE << AR933X_UART_CS_IF_MODE_S);
++
+       spin_unlock_irqrestore(&up->port.lock, flags);
+ 
+       if (tty_termios_baud_rate(new))
+@@ -401,6 +471,8 @@ static void ar933x_uart_config_port(stru
+ static int ar933x_uart_verify_port(struct uart_port *port,
+                                  struct serial_struct *ser)
+ {
++      struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
++
+       if (ser->type != PORT_UNKNOWN &&
+           ser->type != PORT_AR933X)
+               return -EINVAL;
+@@ -408,7 +480,8 @@ static int ar933x_uart_verify_port(struc
+       if (ser->irq < 0 || ser->irq >= NR_IRQS)
+               return -EINVAL;
+ 
+-      if (ser->baud_base < 28800)
++      if (ser->baud_base < up->min_baud ||
++          ser->baud_base > up->max_baud)
+               return -EINVAL;
+ 
+       return 0;
+@@ -561,6 +634,7 @@ static int __devinit ar933x_uart_probe(s
+       struct uart_port *port;
+       struct resource *mem_res;
+       struct resource *irq_res;
++      unsigned int baud;
+       int id;
+       int ret;
+ 
+@@ -611,6 +685,12 @@ static int __devinit ar933x_uart_probe(s
+       port->fifosize = AR933X_UART_FIFO_SIZE;
+       port->ops = &ar933x_uart_ops;
+ 
++      baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
++      up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
++
++      baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
++      up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
++
+       ar933x_uart_add_console_port(up);
+ 
+       ret = uart_add_one_port(&ar933x_uart_driver, &up->port);