Commit 01f56abd authored by Saleem Abdulrasool's avatar Saleem Abdulrasool Committed by Greg Kroah-Hartman
Browse files

imx: add polled io uart methods 



These methods are invoked if the iMX uart is used in conjuction with kgdb during
early boot.  In order to access the UART without the interrupts, the kernel uses
the basic polling methods for IO with the device.  With these methods
implemented, it is now possible to enable kgdb during early boot over serial.

Signed-off-by: default avatarSaleem Abdulrasool <compnerd@compnerd.org>
Signed-off-by: default avatarDirk Behme <dirk.behme@gmail.com>
CC: Sascha Hauer <s.hauer@pengutronix.de>
CC: Fabio Estevam <festevam@gmail.com>
CC: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
CC: linux-serial@vger.kernel.org
CC: Alan Cox <alan@linux.intel.com>
Signed-off-by: default avatarShawn Guo <shawn.guo@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 0ad5a814

drivers/tty/serial/imx.c

+69 −0
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ 
#define  UCR2_STPB       (1<<6)	 /* Stop */

#define  UCR2_WS         (1<<5)	 /* Word size */

#define  UCR2_RTSEN      (1<<4)	 /* Request to send interrupt enable */

#define  UCR2_ATEN       (1<<3)  /* Aging Timer Enable */

#define  UCR2_TXEN       (1<<2)	 /* Transmitter enabled */

#define  UCR2_RXEN       (1<<1)	 /* Receiver enabled */

#define  UCR2_SRST 	 (1<<0)	 /* SW reset */
@@ -1109,6 +1110,70 @@ imx_verify_port(struct uart_port *port, struct serial_struct *ser) 
	return ret;

}



#if defined(CONFIG_CONSOLE_POLL)

static int imx_poll_get_char(struct uart_port *port)

{

	struct imx_port_ucrs old_ucr;

	unsigned int status;

	unsigned char c;



	/* save control registers */

	imx_port_ucrs_save(port, &old_ucr);



	/* disable interrupts */

	writel(UCR1_UARTEN, port->membase + UCR1);

	writel(old_ucr.ucr2 & ~(UCR2_ATEN | UCR2_RTSEN | UCR2_ESCI),

	       port->membase + UCR2);

	writel(old_ucr.ucr3 & ~(UCR3_DCD | UCR3_RI | UCR3_DTREN),

	       port->membase + UCR3);



	/* poll */

	do {

		status = readl(port->membase + USR2);

	} while (~status & USR2_RDR);



	/* read */

	c = readl(port->membase + URXD0);



	/* restore control registers */

	imx_port_ucrs_restore(port, &old_ucr);



	return c;

}



static void imx_poll_put_char(struct uart_port *port, unsigned char c)

{

	struct imx_port_ucrs old_ucr;

	unsigned int status;



	/* save control registers */

	imx_port_ucrs_save(port, &old_ucr);



	/* disable interrupts */

	writel(UCR1_UARTEN, port->membase + UCR1);

	writel(old_ucr.ucr2 & ~(UCR2_ATEN | UCR2_RTSEN | UCR2_ESCI),

	       port->membase + UCR2);

	writel(old_ucr.ucr3 & ~(UCR3_DCD | UCR3_RI | UCR3_DTREN),

	       port->membase + UCR3);



	/* drain */

	do {

		status = readl(port->membase + USR1);

	} while (~status & USR1_TRDY);



	/* write */

	writel(c, port->membase + URTX0);



	/* flush */

	do {

		status = readl(port->membase + USR2);

	} while (~status & USR2_TXDC);



	/* restore control registers */

	imx_port_ucrs_restore(port, &old_ucr);

}

#endif



static struct uart_ops imx_pops = {

	.tx_empty	= imx_tx_empty,

	.set_mctrl	= imx_set_mctrl,
@@ -1126,6 +1191,10 @@ static struct uart_ops imx_pops = { 
	.request_port	= imx_request_port,

	.config_port	= imx_config_port,

	.verify_port	= imx_verify_port,

#if defined(CONFIG_CONSOLE_POLL)

	.poll_get_char  = imx_poll_get_char,

	.poll_put_char  = imx_poll_put_char,

#endif

};



static struct imx_port *imx_ports[UART_NR];

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