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Commit e36361d7 authored by Andreas Färber's avatar Andreas Färber Committed by Greg Kroah-Hartman
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tty: serial: Add Actions Semi Owl UART earlycon 



This implements an earlycon for Actions Semi S500/S900 SoCs.

Based on LeMaker linux-actions tree.

Signed-off-by: default avatarAndreas Färber <afaerber@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 80b208ed

Documentation/admin-guide/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -945,6 +945,12 @@ 
			must already be setup and configured. Options are not

			yet supported.



		owl,<addr>

			Start an early, polled-mode console on a serial port

			of an Actions Semi SoC, such as S500 or S900, at the

			specified address. The serial port must already be

			setup and configured. Options are not yet supported.



		smh	Use ARM semihosting calls for early console.



		s3c2410,<addr>

drivers/tty/serial/Kconfig

+19 −0
Original line number Diff line number Diff line
@@ -1688,6 +1688,25 @@ config SERIAL_MVEBU_CONSOLE 
	  and warnings and which allows logins in single user mode)

	  Otherwise, say 'N'.



config SERIAL_OWL

	bool "Actions Semi Owl serial port support"

	depends on ARCH_ACTIONS || COMPILE_TEST

	select SERIAL_CORE

	help

	  This driver is for Actions Semiconductor S500/S900 SoC's UART.

	  Say 'Y' here if you wish to use the on-board serial port.

	  Otherwise, say 'N'.



config SERIAL_OWL_CONSOLE

	bool "Console on Actions Semi Owl serial port"

	depends on SERIAL_OWL=y

	select SERIAL_CORE_CONSOLE

	select SERIAL_EARLYCON

	default y

	help

	  Say 'Y' here if you wish to use Actions Semiconductor S500/S900 UART

	  as the system console. Only earlycon is implemented currently.



endmenu



config SERIAL_MCTRL_GPIO

drivers/tty/serial/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ obj-$(CONFIG_SERIAL_STM32) += stm32-usart.o 
obj-$(CONFIG_SERIAL_MVEBU_UART)	+= mvebu-uart.o

obj-$(CONFIG_SERIAL_PIC32)	+= pic32_uart.o

obj-$(CONFIG_SERIAL_MPS2_UART)	+= mps2-uart.o

obj-$(CONFIG_SERIAL_OWL)	+= owl-uart.o



# GPIOLIB helpers for modem control lines

obj-$(CONFIG_SERIAL_MCTRL_GPIO)	+= serial_mctrl_gpio.o

drivers/tty/serial/owl-uart.c

0 → 100644
+135 −0
Original line number Diff line number Diff line 
/*

 * Actions Semi Owl family serial console

 *

 * Copyright 2013 Actions Semi Inc.

 * Author: Actions Semi, Inc.

 *

 * Copyright (c) 2016-2017 Andreas Färber

 *

 * This program is free software; you can redistribute  it and/or modify it

 * under  the terms of  the GNU General  Public License as published by the

 * Free Software Foundation;  either version 2 of the  License, or (at your

 * option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. If not, see <http://www.gnu.org/licenses/>.

 */



#include <linux/console.h>

#include <linux/delay.h>

#include <linux/io.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>

#include <linux/serial.h>

#include <linux/serial_core.h>



#define OWL_UART_CTL	0x000

#define OWL_UART_TXDAT	0x008

#define OWL_UART_STAT	0x00c



#define OWL_UART_CTL_TRFS_TX		BIT(14)

#define OWL_UART_CTL_EN			BIT(15)

#define OWL_UART_CTL_RXIE		BIT(18)

#define OWL_UART_CTL_TXIE		BIT(19)



#define OWL_UART_STAT_RIP		BIT(0)

#define OWL_UART_STAT_TIP		BIT(1)

#define OWL_UART_STAT_TFFU		BIT(6)

#define OWL_UART_STAT_TRFL_MASK		(0x1f << 11)

#define OWL_UART_STAT_UTBB		BIT(17)



static inline void owl_uart_write(struct uart_port *port, u32 val, unsigned int off)

{

	writel(val, port->membase + off);

}



static inline u32 owl_uart_read(struct uart_port *port, unsigned int off)

{

	return readl(port->membase + off);

}



#ifdef CONFIG_SERIAL_OWL_CONSOLE



static void owl_console_putchar(struct uart_port *port, int ch)

{

	if (!port->membase)

		return;



	while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)

		cpu_relax();



	owl_uart_write(port, ch, OWL_UART_TXDAT);

}



static void owl_uart_port_write(struct uart_port *port, const char *s,

				u_int count)

{

	u32 old_ctl, val;

	unsigned long flags;

	int locked;



	local_irq_save(flags);



	if (port->sysrq)

		locked = 0;

	else if (oops_in_progress)

		locked = spin_trylock(&port->lock);

	else {

		spin_lock(&port->lock);

		locked = 1;

	}



	old_ctl = owl_uart_read(port, OWL_UART_CTL);

	val = old_ctl | OWL_UART_CTL_TRFS_TX;

	/* disable IRQ */

	val &= ~(OWL_UART_CTL_RXIE | OWL_UART_CTL_TXIE);

	owl_uart_write(port, val, OWL_UART_CTL);



	uart_console_write(port, s, count, owl_console_putchar);



	/* wait until all contents have been sent out */

	while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TRFL_MASK)

		cpu_relax();



	/* clear IRQ pending */

	val = owl_uart_read(port, OWL_UART_STAT);

	val |= OWL_UART_STAT_TIP | OWL_UART_STAT_RIP;

	owl_uart_write(port, val, OWL_UART_STAT);



	owl_uart_write(port, old_ctl, OWL_UART_CTL);



	if (locked)

		spin_unlock(&port->lock);



	local_irq_restore(flags);

}



static void owl_uart_early_console_write(struct console *co,

					 const char *s,

					 u_int count)

{

	struct earlycon_device *dev = co->data;



	owl_uart_port_write(&dev->port, s, count);

}



static int __init

owl_uart_early_console_setup(struct earlycon_device *device, const char *opt)

{

	if (!device->port.membase)

		return -ENODEV;



	device->con->write = owl_uart_early_console_write;



	return 0;

}

OF_EARLYCON_DECLARE(owl, "actions,owl-uart",

		    owl_uart_early_console_setup);



#endif /* CONFIG_SERIAL_OWL_CONSOLE */