Commit ac3e3fb4 authored by Linus Walleij's avatar Linus Walleij Committed by Russell King
Browse files

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: default avatarMarcin Mielczarczyk <marcin.mielczarczyk@tieto.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@stericsson.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent ec489aa8

drivers/serial/amba-pl011.c

+25 −2
Original line number Diff line number Diff line
@@ -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;

include/linux/amba/serial.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

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