tty/serial/ar933x_uart: fix baud rate calculation
The UART of the AR933x SoC implements a fractional divisor
for generating the desired baud rate.
The current code uses a fixed value for the fractional
part of the divisor, and this leads to improperly
calculated baud rates:
baud scale step real baud diff
300 5207* 8192 17756 17456 5818.66%
600 2603* 8192 35511 34911 5818.50%
1200 1301* 8192 71023 69823 5818.58%
2400 650* 8192 11241 8841 368.37%
4800 324* 8192 22645 17845 371.77%
9600 161 8192 9645 45 0.46%
14400 107 8192 14468 68 0.47%
19200 80 8192 19290 90 0.46%
28800 53 8192 28935 135 0.46%
38400 39 8192 39063 663 1.72%
57600 26 8192 57870 270 0.46%
115200 12 8192 120192 4992 4.33%
230400 5 8192 260417 30017 13.02%
460800 2 8192 520833 60033 13.02%
921600 0 8192 1562500 640900 69.93%
After the patch, the integer and fractional parts of the
divisor will be calculated dynamically. This ensures that
the UART will use correct baud rates:
baud scale step real baud diff
300 6 11 300 0 0.00%
600 54 173 600 0 0.00%
1200 30 195 1200 0 0.00%
2400 30 390 2400 0 0.00%
4800 48 1233 4800 0 0.00%
9600 78 3976 9600 0 0.00%
14400 98 7474 14400 0 0.00%
19200 55 5637 19200 0 0.00%
28800 130 19780 28800 0 0.00%
38400 36 7449 38400 0 0.00%
57600 78 23857 57600 0 0.00%
115200 43 26575 115200 0 0.00%
230400 23 28991 230400 0 0.00%
460800 11 28991 460800 0 0.00%
921600 5 28991 921599 -1 0.00%
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Gabor Juhos
Greg Kroah-Hartman
parent
5318609519
commit
2dff8ad926
|
|
@ -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_driver;
|
|||
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 uart_port *port)
|
|||
{
|
||||
}
|
||||
|
||||
/*
|
||||
* 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(struct uart_port *port,
|
|||
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(struct uart_port *port,
|
|||
/* 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(struct uart_port *port,
|
|||
*/
|
||||
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(struct uart_port *port,
|
|||
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(struct uart_port *port,
|
|||
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(struct uart_port *port, int flags)
|
|||
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(struct uart_port *port,
|
|||
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(struct platform_device *pdev)
|
|||
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(struct platform_device *pdev)
|
|||
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);
|
||||
|
|
|
|||
Loading…
Reference in New Issue