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ARM: 6158/2: PL011 baudrate extension for ST-Ericssons derivative 

Implementation of the ST-Ericsson baudrate extension in the PL011
block. In this modified variant it is possible to change the
sampling factor from 16 to 8, and thanks to this we can get higher
baudrates while still using the same peripheral clock.

Also replace the simple division to determine the baud divisor
with DIV_ROUND_CLOSEST() rather than a simple integer division.

Cc: Alessandro Rubini <rubini@unipv.it>
Cc: Jerzy Kasenberg <jerzy.kasenberg@tieto.com>
Signed-off-by: Marcin Mielczarczyk <marcin.mielczarczyk@tieto.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Linus Walleij 2010-06-02 20:40:22 +01:00 committed by Russell King
parent ec489aa8f9
commit ac3e3fb424
2 changed files with 26 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
drivers/serial/amba-pl011.c
View File

@ -74,6 +74,7 @@ struct uart_amba_port {
unsigned int ifls; /* vendor-specific */
unsigned int lcrh_tx; /* vendor-specific */
unsigned int lcrh_rx; /* vendor-specific */
bool oversampling; /* vendor-specific */
bool autorts;
};
@ -83,6 +84,7 @@ struct vendor_data {
unsigned int fifosize;
unsigned int lcrh_tx;
unsigned int lcrh_rx;
bool oversampling;
};
static struct vendor_data vendor_arm = {
@ -90,6 +92,7 @@ static struct vendor_data vendor_arm = {
.fifosize = 16,
.lcrh_tx = UART011_LCRH,
.lcrh_rx = UART011_LCRH,
.oversampling = false,
};
static struct vendor_data vendor_st = {
@ -97,6 +100,7 @@ static struct vendor_data vendor_st = {
.fifosize = 64,
.lcrh_tx = ST_UART011_LCRH_TX,
.lcrh_rx = ST_UART011_LCRH_RX,
.oversampling = true,
};
static void pl011_stop_tx(struct uart_port *port)
@ -499,8 +503,13 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
/*
* Ask the core to calculate the divisor for us.
*/
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
quot = port->uartclk * 4 / baud;
baud = uart_get_baud_rate(port, termios, old, 0,
port->uartclk/(uap->oversampling ? 8 : 16));
if (baud > port->uartclk/16)
quot = DIV_ROUND_CLOSEST(port->uartclk * 8, baud);
else
quot = DIV_ROUND_CLOSEST(port->uartclk * 4, baud);
switch (termios->c_cflag & CSIZE) {
case CS5:
@ -579,6 +588,13 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
uap->autorts = false;
}
if (uap->oversampling) {
if (baud > port->uartclk/16)
old_cr |= ST_UART011_CR_OVSFACT;
else
old_cr &= ~ST_UART011_CR_OVSFACT;
}
/* Set baud rate */
writew(quot & 0x3f, port->membase + UART011_FBRD);
writew(quot >> 6, port->membase + UART011_IBRD);
@ -744,6 +760,12 @@ pl011_console_get_options(struct uart_amba_port *uap, int *baud,
fbrd = readw(uap->port.membase + UART011_FBRD);
*baud = uap->port.uartclk * 4 / (64 * ibrd + fbrd);
if (uap->oversampling) {
if (readw(uap->port.membase + UART011_CR)
& ST_UART011_CR_OVSFACT)
*baud *= 2;
}
}
}
@ -839,6 +861,7 @@ static int pl011_probe(struct amba_device *dev, struct amba_id *id)
uap->ifls = vendor->ifls;
uap->lcrh_rx = vendor->lcrh_rx;
uap->lcrh_tx = vendor->lcrh_tx;
uap->oversampling = vendor->oversampling;
uap->port.dev = &dev->dev;
uap->port.mapbase = dev->res.start;
uap->port.membase = base;

1
include/linux/amba/serial.h
View File

@ -86,6 +86,7 @@
#define UART010_CR_TIE 0x0020
#define UART010_CR_RIE 0x0010
#define UART010_CR_MSIE 0x0008
#define ST_UART011_CR_OVSFACT 0x0008 /* Oversampling factor */
#define UART01x_CR_IIRLP 0x0004 /* SIR low power mode */
#define UART01x_CR_SIREN 0x0002 /* SIR enable */
#define UART01x_CR_UARTEN 0x0001 /* UART enable */