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Commit 0d1f22e4 authored by Albrecht Dreß's avatar Albrecht Dreß Committed by Grant Likely
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powerpc/5200: improve uart baud rate calculation (reach high baud rates, better accuracy) 



On the MPC5200B, make very high baud rates (e.g. 3 MBaud) accessible and
achieve a higher precision for high baud rates in general.  This is done by
selecting the appropriate prescaler (/4 or /32).  As to keep the code clean,
the getuartclk method has been dropped, and all calculations are done in a
new set_baudrate method.

Notes: only "fsl,mpc5200b-psc-uart" compatible devices benefit from these
improvements.

Tested on a custom 5200B based board, from 110 baud up to 3 MBaud, and with
both "fsl,mpc5200b-psc-uart" and "fsl,mpc5200-psc-uart" devices.
Also tested on the mpc5121ads board.

Signed-off-by: default avatarAlbrecht Dreß <albrecht.dress@arcor.de>
[agust: fixed mpc5121 prescaler comment]
Signed-off-by: default avatarAnatolij Gustschin <agust@denx.de>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent b37fa16e

drivers/serial/mpc52xx_uart.c

+116 −29
Original line number Diff line number Diff line
@@ -113,7 +113,9 @@ struct psc_ops { 
	unsigned char	(*read_char)(struct uart_port *port);

	void		(*cw_disable_ints)(struct uart_port *port);

	void		(*cw_restore_ints)(struct uart_port *port);

	unsigned long	(*getuartclk)(void *p);

	unsigned int	(*set_baudrate)(struct uart_port *port,

					struct ktermios *new,

					struct ktermios *old);

	int		(*clock)(struct uart_port *port, int enable);

	int		(*fifoc_init)(void);

	void		(*fifoc_uninit)(void);
@@ -121,6 +123,16 @@ struct psc_ops { 
	irqreturn_t	(*handle_irq)(struct uart_port *port);

};



/* setting the prescaler and divisor reg is common for all chips */

static inline void mpc52xx_set_divisor(struct mpc52xx_psc __iomem *psc,

				       u16 prescaler, unsigned int divisor)

{

	/* select prescaler */

	out_be16(&psc->mpc52xx_psc_clock_select, prescaler);

	out_8(&psc->ctur, divisor >> 8);

	out_8(&psc->ctlr, divisor & 0xff);

}



#ifdef CONFIG_PPC_MPC52xx

#define FIFO_52xx(port) ((struct mpc52xx_psc_fifo __iomem *)(PSC(port)+1))

static void mpc52xx_psc_fifo_init(struct uart_port *port)
@@ -128,9 +140,6 @@ static void mpc52xx_psc_fifo_init(struct uart_port *port) 
	struct mpc52xx_psc __iomem *psc = PSC(port);

	struct mpc52xx_psc_fifo __iomem *fifo = FIFO_52xx(port);



	/* /32 prescaler */

	out_be16(&psc->mpc52xx_psc_clock_select, 0xdd00);



	out_8(&fifo->rfcntl, 0x00);

	out_be16(&fifo->rfalarm, 0x1ff);

	out_8(&fifo->tfcntl, 0x07);
@@ -219,15 +228,47 @@ static void mpc52xx_psc_cw_restore_ints(struct uart_port *port) 
	out_be16(&PSC(port)->mpc52xx_psc_imr, port->read_status_mask);

}



/* Search for bus-frequency property in this node or a parent */

static unsigned long mpc52xx_getuartclk(void *p)

static unsigned int mpc5200_psc_set_baudrate(struct uart_port *port,

					     struct ktermios *new,

					     struct ktermios *old)

{

	/*

	 * 5200 UARTs have a / 32 prescaler

	 * but the generic serial code assumes 16

	 * so return ipb freq / 2

	 */

	return mpc5xxx_get_bus_frequency(p) / 2;

	unsigned int baud;

	unsigned int divisor;



	/* The 5200 has a fixed /32 prescaler, uartclk contains the ipb freq */

	baud = uart_get_baud_rate(port, new, old,

				  port->uartclk / (32 * 0xffff) + 1,

				  port->uartclk / 32);

	divisor = (port->uartclk + 16 * baud) / (32 * baud);



	/* enable the /32 prescaler and set the divisor */

	mpc52xx_set_divisor(PSC(port), 0xdd00, divisor);

	return baud;

}



static unsigned int mpc5200b_psc_set_baudrate(struct uart_port *port,

					      struct ktermios *new,

					      struct ktermios *old)

{

	unsigned int baud;

	unsigned int divisor;

	u16 prescaler;



	/* The 5200B has a selectable /4 or /32 prescaler, uartclk contains the

	 * ipb freq */

	baud = uart_get_baud_rate(port, new, old,

				  port->uartclk / (32 * 0xffff) + 1,

				  port->uartclk / 4);

	divisor = (port->uartclk + 2 * baud) / (4 * baud);



	/* select the proper prescaler and set the divisor */

	if (divisor > 0xffff) {

		divisor = (divisor + 4) / 8;

		prescaler = 0xdd00; /* /32 */

	} else

		prescaler = 0xff00; /* /4 */

	mpc52xx_set_divisor(PSC(port), prescaler, divisor);

	return baud;

}



static void mpc52xx_psc_get_irq(struct uart_port *port, struct device_node *np)
@@ -258,7 +299,28 @@ static struct psc_ops mpc52xx_psc_ops = { 
	.read_char = mpc52xx_psc_read_char,

	.cw_disable_ints = mpc52xx_psc_cw_disable_ints,

	.cw_restore_ints = mpc52xx_psc_cw_restore_ints,

	.getuartclk = mpc52xx_getuartclk,

	.set_baudrate = mpc5200_psc_set_baudrate,

	.get_irq = mpc52xx_psc_get_irq,

	.handle_irq = mpc52xx_psc_handle_irq,

};



static struct psc_ops mpc5200b_psc_ops = {

	.fifo_init = mpc52xx_psc_fifo_init,

	.raw_rx_rdy = mpc52xx_psc_raw_rx_rdy,

	.raw_tx_rdy = mpc52xx_psc_raw_tx_rdy,

	.rx_rdy = mpc52xx_psc_rx_rdy,

	.tx_rdy = mpc52xx_psc_tx_rdy,

	.tx_empty = mpc52xx_psc_tx_empty,

	.stop_rx = mpc52xx_psc_stop_rx,

	.start_tx = mpc52xx_psc_start_tx,

	.stop_tx = mpc52xx_psc_stop_tx,

	.rx_clr_irq = mpc52xx_psc_rx_clr_irq,

	.tx_clr_irq = mpc52xx_psc_tx_clr_irq,

	.write_char = mpc52xx_psc_write_char,

	.read_char = mpc52xx_psc_read_char,

	.cw_disable_ints = mpc52xx_psc_cw_disable_ints,

	.cw_restore_ints = mpc52xx_psc_cw_restore_ints,

	.set_baudrate = mpc5200b_psc_set_baudrate,

	.get_irq = mpc52xx_psc_get_irq,

	.handle_irq = mpc52xx_psc_handle_irq,

};
@@ -392,9 +454,35 @@ static void mpc512x_psc_cw_restore_ints(struct uart_port *port) 
	out_be32(&FIFO_512x(port)->rximr, port->read_status_mask & 0x7f);

}



static unsigned long mpc512x_getuartclk(void *p)

static unsigned int mpc512x_psc_set_baudrate(struct uart_port *port,

					     struct ktermios *new,

					     struct ktermios *old)

{

	return mpc5xxx_get_bus_frequency(p);

	unsigned int baud;

	unsigned int divisor;



	/*

	 * The "MPC5121e Microcontroller Reference Manual, Rev. 3" says on

	 * pg. 30-10 that the chip supports a /32 and a /10 prescaler.

	 * Furthermore, it states that "After reset, the prescaler by 10

	 * for the UART mode is selected", but the reset register value is

	 * 0x0000 which means a /32 prescaler. This is wrong.

	 *

	 * In reality using /32 prescaler doesn't work, as it is not supported!

	 * Use /16 or /10 prescaler, see "MPC5121e Hardware Design Guide",

	 * Chapter 4.1 PSC in UART Mode.

	 * Calculate with a /16 prescaler here.

	 */



	/* uartclk contains the ips freq */

	baud = uart_get_baud_rate(port, new, old,

				  port->uartclk / (16 * 0xffff) + 1,

				  port->uartclk / 16);

	divisor = (port->uartclk + 8 * baud) / (16 * baud);



	/* enable the /16 prescaler and set the divisor */

	mpc52xx_set_divisor(PSC(port), 0xdd00, divisor);

	return baud;

}



/* Init PSC FIFO Controller */
@@ -498,7 +586,7 @@ static struct psc_ops mpc512x_psc_ops = { 
	.read_char = mpc512x_psc_read_char,

	.cw_disable_ints = mpc512x_psc_cw_disable_ints,

	.cw_restore_ints = mpc512x_psc_cw_restore_ints,

	.getuartclk = mpc512x_getuartclk,

	.set_baudrate = mpc512x_psc_set_baudrate,

	.clock = mpc512x_psc_clock,

	.fifoc_init = mpc512x_psc_fifoc_init,

	.fifoc_uninit = mpc512x_psc_fifoc_uninit,
@@ -666,8 +754,8 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct ktermios *new, 
	struct mpc52xx_psc __iomem *psc = PSC(port);

	unsigned long flags;

	unsigned char mr1, mr2;

	unsigned short ctr;

	unsigned int j, baud, quot;

	unsigned int j;

	unsigned int baud;



	/* Prepare what we're gonna write */

	mr1 = 0;
@@ -704,16 +792,9 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct ktermios *new, 
		mr2 |= MPC52xx_PSC_MODE_TXCTS;

	}



	baud = uart_get_baud_rate(port, new, old, 0, port->uartclk/16);

	quot = uart_get_divisor(port, baud);

	ctr = quot & 0xffff;



	/* Get the lock */

	spin_lock_irqsave(&port->lock, flags);



	/* Update the per-port timeout */

	uart_update_timeout(port, new->c_cflag, baud);



	/* Do our best to flush TX & RX, so we don't lose anything */

	/* But we don't wait indefinitely ! */

	j = 5000000;	/* Maximum wait */
@@ -737,8 +818,10 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct ktermios *new, 
	out_8(&psc->command, MPC52xx_PSC_SEL_MODE_REG_1);

	out_8(&psc->mode, mr1);

	out_8(&psc->mode, mr2);

	out_8(&psc->ctur, ctr >> 8);

	out_8(&psc->ctlr, ctr & 0xff);

	baud = psc_ops->set_baudrate(port, new, old);



	/* Update the per-port timeout */

	uart_update_timeout(port, new->c_cflag, baud);



	if (UART_ENABLE_MS(port, new->c_cflag))

		mpc52xx_uart_enable_ms(port);
@@ -1118,7 +1201,7 @@ mpc52xx_console_setup(struct console *co, char *options) 
		return ret;

	}



	uartclk = psc_ops->getuartclk(np);

	uartclk = mpc5xxx_get_bus_frequency(np);

	if (uartclk == 0) {

		pr_debug("Could not find uart clock frequency!\n");

		return -EINVAL;
@@ -1201,6 +1284,7 @@ static struct uart_driver mpc52xx_uart_driver = { 


static struct of_device_id mpc52xx_uart_of_match[] = {

#ifdef CONFIG_PPC_MPC52xx

	{ .compatible = "fsl,mpc5200b-psc-uart", .data = &mpc5200b_psc_ops, },

	{ .compatible = "fsl,mpc5200-psc-uart", .data = &mpc52xx_psc_ops, },

	/* binding used by old lite5200 device trees: */

	{ .compatible = "mpc5200-psc-uart", .data = &mpc52xx_psc_ops, },
@@ -1233,7 +1317,10 @@ mpc52xx_uart_of_probe(struct of_device *op, const struct of_device_id *match) 
	pr_debug("Found %s assigned to ttyPSC%x\n",

		 mpc52xx_uart_nodes[idx]->full_name, idx);



	uartclk = psc_ops->getuartclk(op->dev.of_node);

	/* set the uart clock to the input clock of the psc, the different

	 * prescalers are taken into account in the set_baudrate() methods

	 * of the respective chip */

	uartclk = mpc5xxx_get_bus_frequency(op->dev.of_node);

	if (uartclk == 0) {

		dev_dbg(&op->dev, "Could not find uart clock frequency!\n");

		return -EINVAL;