mpc5200b/uart: improve 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.
The 512x may or may not work; the patch keeps the current implementation (using a /16 prescaler), but according to the data sheet, this is plain wrong. See the comment in mpc512x_psc_set_baudrate(). Any insight and testing of the code (maybe Anatolij, when he's back from his vacation) would be appreciated.

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.

---

Change vs. v.3: re-based against Linus' git tree (2.6.34-rc1-dirty)

index 3119fdd..e349514 100644
@@ -146,7 +146,9 @@ 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);

@@ -154,6 +156,16 @@ struct psc_ops {
 	irqreturn_t	(*handle_irq)(struct uart_port *port);
 };

=20
+/* 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)
@@ -161,9 +173,6 @@ static void mpc52xx_psc_fifo_init(struct uart_port *por=
t)
struct mpc52xx_psc __iomem *psc =3D PSC(port);
struct mpc52xx_psc_fifo __iomem *fifo =3D FIFO_52xx(port);
=20
- /* /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);
@@ -252,15 +261,47 @@ static void mpc52xx_psc_cw_restore_ints(struct uart_p= ort *port)
out_be16(&PSC(port)->mpc52xx_psc_imr, port->read_status_mask);
}
=20
-/* 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 =3D uart_get_baud_rate(port, new, old,
+ port->uartclk / (32 * 0xffff) + 1,
+ port->uartclk / 32);
+ divisor =3D (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 =3D uart_get_baud_rate(port, new, old,
+ port->uartclk / (32 * 0xffff) + 1,
+ port->uartclk / 4);
+ divisor =3D (port->uartclk + 2 * baud) / (4 * baud);
+
+ /* select the proper prescaler and set the divisor */
+ if (divisor > 0xffff) {
+ divisor =3D (divisor + 4) / 8;
+ prescaler =3D 0xdd00; /* /32 */
+ } else
+ prescaler =3D 0xff00; /* /4 */
+ mpc52xx_set_divisor(PSC(port), prescaler, divisor);
+ return baud;
}
=20
static void mpc52xx_psc_get_irq(struct uart_port *port, struct device_node= *np)
@@ -291,7 +332,28 @@ static struct psc_ops mpc52xx_psc_ops =3D {
.read_char =3D mpc52xx_psc_read_char,
.cw_disable_ints =3D mpc52xx_psc_cw_disable_ints, .cw_restore_ints =3D mpc52xx_psc_cw_restore_ints,
- .getuartclk =3D mpc52xx_getuartclk,
+ .set_baudrate =3D mpc5200_psc_set_baudrate,
+ .get_irq =3D mpc52xx_psc_get_irq,
+ .handle_irq =3D mpc52xx_psc_handle_irq,
+};
+
+static struct psc_ops mpc5200b_psc_ops =3D {
+ .fifo_init =3D mpc52xx_psc_fifo_init,
+ .raw_rx_rdy =3D mpc52xx_psc_raw_rx_rdy,
+ .raw_tx_rdy =3D mpc52xx_psc_raw_tx_rdy,
+ .rx_rdy =3D mpc52xx_psc_rx_rdy,
+ .tx_rdy =3D mpc52xx_psc_tx_rdy,
+ .tx_empty =3D mpc52xx_psc_tx_empty,
+ .stop_rx =3D mpc52xx_psc_stop_rx,
+ .start_tx =3D mpc52xx_psc_start_tx,
+ .stop_tx =3D mpc52xx_psc_stop_tx,
+ .rx_clr_irq =3D mpc52xx_psc_rx_clr_irq,
+ .tx_clr_irq =3D mpc52xx_psc_tx_clr_irq,
+ .write_char =3D mpc52xx_psc_write_char,
+ .read_char =3D mpc52xx_psc_read_char,
+ .cw_disable_ints =3D mpc52xx_psc_cw_disable_ints,
+ .cw_restore_ints =3D mpc52xx_psc_cw_restore_ints,
+ .set_baudrate =3D mpc5200b_psc_set_baudrate,
.get_irq =3D mpc52xx_psc_get_irq,
.handle_irq =3D mpc52xx_psc_handle_irq,
};
@@ -425,9 +487,44 @@ static void mpc512x_psc_cw_restore_ints(struct uart_po= rt *port)
out_be32(&FIFO_512x(port)->rximr, port->read_status_mask & 0x7f);
}
=20
-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;
+
+ /*
+ * FIXME -
+ * since ages, the code calculates with a /16 prescaler, but
+ * never configures it explicitly. 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...
+ *
+ * Thus, using /16 for the calculation might actually be wrong.
+ *
+ * However, U-Boot (in the file cpu/mpc512x/serial.c) also uses a /16
+ * prescaler, activated by 0xdd00 in the csr.
+ *
+ * **Confusion Alert**
+ *
+ * Unfortunately, I don't have a 512x system, so I cannot what happens
+ * in reality...
+ *
+ * Albrecht Dre=DF <[email protected]>, 2010-MAR-04
+ */
+
+ /* uartclk contains the ips freq */
+ baud =3D uart_get_baud_rate(port, new, old,
+ port->uartclk / (16 * 0xffff) + 1,
+ port->uartclk / 16);
+ divisor =3D (port->uartclk + 8 * baud) / (16 * baud);
+
+ /* FIXME - see above, shamelessly stolen from U-Boot */
+ mpc52xx_set_divisor(PSC(port), 0xdd00, divisor);
+ return baud;
}
=20
#define DEFAULT_FIFO_SIZE 16
@@ -600,7 +697,7 @@ static struct psc_ops mpc512x_psc_ops =3D {
.read_char =3D mpc512x_psc_read_char,
.cw_disable_ints =3D mpc512x_psc_cw_disable_ints, .cw_restore_ints =3D mpc512x_psc_cw_restore_ints,
- .getuartclk =3D mpc512x_getuartclk,
+ .set_baudrate =3D mpc512x_psc_set_baudrate,
.clock =3D mpc512x_psc_clock,
.fifoc_init =3D mpc512x_psc_fifoc_init,
.fifoc_uninit =3D mpc512x_psc_fifoc_uninit,
@@ -768,8 +865,8 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct=
ktermios *new,
struct mpc52xx_psc __iomem *psc =3D PSC(port);
unsigned long flags;
unsigned char mr1, mr2;
- unsigned short ctr;
- unsigned int j, baud, quot;
+ unsigned int j;
+ unsigned int baud;
=20
/* Prepare what we're gonna write */
mr1 =3D 0;
@@ -806,16 +903,9 @@ mpc52xx_uart_set_termios(struct uart_port *port, struc= t ktermios *new,
mr2 |=3D MPC52xx_PSC_MODE_TXCTS;
}
=20
- baud =3D uart_get_baud_rate(port, new, old, 0, port->uartclk/16);
- quot =3D uart_get_divisor(port, baud);
- ctr =3D quot & 0xffff;
-
/* Get the lock */
spin_lock_irqsave(&port->lock, flags);
=20
- /* 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 =3D 5000000; /* Maximum wait */
@@ -839,8 +929,10 @@ mpc52xx_uart_set_termios(struct uart_port *port, struc= t 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 =3D psc_ops->set_baudrate(port, new, old);
+
+ /* Update the per-port timeout */
+ uart_update_timeout(port, new->c_cflag, baud);
=20
if (UART_ENABLE_MS(port, new->c_cflag))
mpc52xx_uart_enable_ms(port);
@@ -1220,7 +1312,7 @@ mpc52xx_console_setup(struct console *co, char *optio= ns)
return ret;
}
=20
- uartclk =3D psc_ops->getuartclk(np);
+ uartclk =3D mpc5xxx_get_bus_frequency(np);
if (uartclk =3D=3D 0) {
pr_debug("Could not find uart clock frequency!\n"); return -EINVAL;
@@ -1303,6 +1395,7 @@ static struct uart_driver mpc52xx_uart_driver =3D { =20
static struct of_device_id mpc52xx_uart_of_match[] =3D {
#ifdef CONFIG_PPC_MPC52xx
+ { .compatible =3D "fsl,mpc5200b-psc-uart", .data =3D &mpc5200b_psc_ops, }=
,
{ .compatible =3D "fsl,mpc5200-psc-uart", .data =3D &mpc52xx_psc_ops, }, /* binding used by old lite5200 device trees: */
{ .compatible =3D "mpc5200-psc-uart", .data =3D &mpc52xx_psc_ops, },
@@ -1335,7 +1428,10 @@ mpc52xx_uart_of_probe(struct of_device *op, const st= ruct of_device_id *match)
pr_debug("Found %s assigned to ttyPSC%x\n",
mpc52xx_uart_nodes[idx]->full_name, idx);
=20
- uartclk =3D psc_ops->getuartclk(op->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 =3D mpc5xxx_get_bus_frequency(op->node);
if (uartclk =3D=3D 0) {
dev_dbg(&op->dev, "Could not find uart clock frequency!\n"); return -EINVAL;

From: Albrecht Dress <[email protected]>

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.

---
v3a -> v4:
- Commit message cleanup
- Fixed prescaler comment in mpc512x_psc_set_baudrate()
- Fixed white space issues

 drivers/serial/mpc52xx_uart.c |  145 ++++++++++++++++++++++++++++++++--------
 1 files changed, 116 insertions(+), 29 deletions(-)

index 3119fdd..80c8717 100644
@@ -146,7 +146,9 @@ 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);

@@ -154,6 +156,16 @@ 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)

@@ -161,9 +173,6 @@ 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);

@@ -252,15 +261,47 @@ 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)

@@ -291,7 +332,28 @@ 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,
 };

@@ -425,9 +487,35 @@ 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;
 }
 
 #define DEFAULT_FIFO_SIZE 16

@@ -600,7 +688,7 @@ 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,

@@ -768,8 +856,8 @@ 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;

@@ -806,16 +894,9 @@ 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 */

@@ -839,8 +920,10 @@ 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);

@@ -1220,7 +1303,7 @@ 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;

@@ -1303,6 +1386,7 @@ 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, },

@@ -1335,7 +1419,10 @@ 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->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->node);
 	if (uartclk == 0) {
 		dev_dbg(&op->dev, "Could not find uart clock frequency!\n");
 		return -EINVAL;

1.6.3.3