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>
diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index 5644cf2..f67e09d 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -74,6 +74,7 @@
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 @@
unsigned int fifosize;
unsigned int lcrh_tx;
unsigned int lcrh_rx;
+ bool oversampling;
};
static struct vendor_data vendor_arm = {
@@ -90,6 +92,7 @@
.fifosize = 16,
.lcrh_tx = UART011_LCRH,
.lcrh_rx = UART011_LCRH,
+ .oversampling = false,
};
static struct vendor_data vendor_st = {
@@ -97,6 +100,7 @@
.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 @@
/*
* 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 @@
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 @@
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 @@
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;