From f6af8fc492d4e37bd0157ec448f61cdc224e6e80 Mon Sep 17 00:00:00 2001
From: Gabor Juhos <juhosg@openwrt.org>
Date: Wed, 22 Aug 2012 19:11:10 +0000
Subject: ar71xx: fix serial clock calculation on AR933x
Closes #12031.
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@33230 3c298f89-4303-0410-b956-a3cf2f4a3e73
---
...33x_uart-improve-serial-clock-calculation.patch | 181 +++++++++++++++++++++
1 file changed, 181 insertions(+)
create mode 100644 target/linux/ar71xx/patches-3.3/211-ar933x_uart-improve-serial-clock-calculation.patch
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
index 0000000000..510b75ed0f
--- /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);
--
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