Re: [PATCH] serial: DCC(JTAG) serial and console emulation support

[matthieu castet <castet.matthieu@free.fr>]

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Hi,

for the record I attach a modified version of the original samsung one that I did.

I improved a bit the reactivity, and did some hack to make polling in idle loop.
With recent kernel this should be done in a thread with SCHED_IDLE policy.

I also supported board with irq for rx and tx (not sure if the original driver supported it).



Matthieu

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diff --git a/drivers/parrot/serial/dcc.c b/drivers/parrot/serial/dcc.c
new file mode 100644
index 0000000..e778b0c
--- /dev/null
+++ b/drivers/parrot/serial/dcc.c
@@ -0,0 +1,590 @@
+/*
+ *  linux/drivers/serial/dcc_serial.c
+ *
+ *  serial port emulation driver for the JTAG DCC Terminal.
+ *
+ * DCC(JTAG1) protocol version for JTAG ICE/ICD Debuggers:
+ * 	Copyright (C) 2003, 2004, 2005 Hyok S. Choi (hyok.choi@samsung.com)
+ * 	SAMSUNG ELECTRONICS Co.,Ltd.
+ *  Copyright (C) 2008 Parrot SA by matthieu.castet@parrot.com
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ *  Changelog:
+ *   Oct-2003 Hyok S. Choi	Created
+ *   Feb-2004 Hyok S. Choi	Updated for serial_core.c and 2.6 kernel
+ *   Mar-2005 Hyok S. Choi	renamed from T32 to DCC
+ *   Apr-2006 Hyok S. Choi	revised including the MAJOR number
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/tty.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/serial.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/tty_flip.h>
+#include <linux/major.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+
+#include <linux/serial_core.h>
+
+/* for PORT_DCC_JTAG1 */
+#include <mach/parrot_kernel_ids.h>
+
+//#undef CONFIG_ARCH_PARROT
+/* XXX may be use a platform driver for this */
+#ifdef CONFIG_ARCH_PARROT
+#define DCC_IRQ_USED
+#define IRQ_RX 27
+#define IRQ_TX 28
+#else
+/* polling mode */
+#define IRQ_RX 0x12345678
+#define IRQ_TX 0
+
+#warning polling mode
+#endif
+
+#define UART_NR			1	/* we have only one JTAG port */
+
+#ifdef CONFIG_SERIAL_DCC_STDSERIAL
+/* use ttyS for emulation of standard serial driver */
+#define SERIAL_DCC_NAME		"ttyS"
+#define SERIAL_DCC_MAJOR	TTY_MAJOR
+#define SERIAL_DCC_MINOR	64
+#else
+/* use ttyJ0(128) */
+#define SERIAL_DCC_NAME		"ttyJ"
+#define SERIAL_DCC_MAJOR	204
+#define SERIAL_DCC_MINOR	186
+#endif
+
+/* DCC Status Bits */
+#define DCC_STATUS_RX		(1 << 0)
+#define DCC_STATUS_TX		(1 << 1)
+
+/* primitive JTAG1 protocol utilities */
+static inline u32 __dcc_getstatus(void)
+{
+	u32 ret;
+
+	asm __volatile__ ("mrc p14, 0, %0, c0, c0	@ read comms ctrl reg"
+		: "=r" (ret));
+
+	return ret;
+}
+
+static inline unsigned char __dcc_getchar(void)
+{
+	unsigned char c;
+
+	asm __volatile__ ("mrc p14, 0, %0, c1, c0	@ read comms data reg"
+		: "=r" (c));
+
+	return c;
+}
+
+static inline void __dcc_putchar(unsigned char c)
+{
+	asm __volatile__ ("mcr p14, 0, %0, c1, c0	@ write a char"
+		: /* no output register */
+		: "r" (c));
+}
+/* end of JTAG1 dependencies */
+
+static void dcc_serial_tx_chars(struct uart_port *port, int max_count);
+static void dcc_serial_rx_chars(struct uart_port *port);
+#ifdef DCC_IRQ_USED /* real IRQ used */
+/* check if there is a char to read and when don't read too much char */
+#define dcc_serial_tx_ready(port) \
+	((__dcc_getstatus() & DCC_STATUS_TX) == 0)
+
+enum {
+	TX_OFF,
+	TX_ON,
+};
+static int dcc_serial_tx_enable;
+enum {
+	RX_OFF,
+	RX_ON,
+	RX_PAUSE,
+};
+static int dcc_serial_rx_enable;
+/* port locked, interrupts locally disabled */
+static void dcc_serial_start_tx(struct uart_port *port)
+{
+	if (dcc_serial_tx_enable == TX_OFF) {
+		enable_irq(port->irq);
+		dcc_serial_tx_enable = TX_ON;
+	}
+}
+
+/* port locked, interrupts locally disabled */
+static void dcc_serial_stop_tx(struct uart_port *port)
+{
+	if (dcc_serial_tx_enable == TX_ON) {
+		disable_irq(port->irq);
+		dcc_serial_tx_enable = TX_OFF;
+	}
+}
+
+/* port locked, interrupts locally disabled */
+static void dcc_serial_stop_rx(struct uart_port *port)
+{
+	if (dcc_serial_rx_enable == RX_ON) {
+		disable_irq((int)port->membase);
+	}
+	dcc_serial_rx_enable = RX_OFF;
+}
+
+/* port locked, interrupts locally disabled */
+static void dcc_serial_throttle_rx(struct uart_port *port, int stop)
+{
+	if (stop && dcc_serial_rx_enable == RX_ON) {
+		disable_irq((int)port->membase);
+		dcc_serial_rx_enable = RX_PAUSE;
+	}
+	else if (stop == 0 && dcc_serial_rx_enable == RX_PAUSE) {
+		enable_irq((int)port->membase);
+		dcc_serial_rx_enable = RX_ON;
+	}
+}
+
+#if 0
+static void dcc_serial_rx_mchars(struct uart_port *port)
+{
+	int timeout;
+	unsigned int read = 0;
+	unsigned int it = 0;
+	unsigned int it1 = 0;
+	do {
+		timeout = 1000;
+		/* wait for a char */
+		//while ((__dcc_getstatus() & DCC_STATUS_RX) == 0 && timeout-- > 0) {
+		while ((readl(0xfc000008) & 0x08000000) == 0) {
+			cpu_relax();
+		}
+		/* read it */
+		if (timeout >= 0) {
+			if (readl(0xfc000008) & 0x08000000)
+				it++;
+			read++;
+			if (read & 0x100) {
+				printk("dcc_serial stat %u %u %u\n", read, it, it1);
+				read = it = it1 = 0;
+			}
+			dcc_serial_rx_chars(port);
+			if (readl(0xfc000008) & 0x08000000)
+				it1++;
+		}
+	} while (/*timeout >= 0*/1);
+}
+#endif
+#ifdef CONFIG_SERIAL_DCC_IDLE_POLL
+int dcc_idle(void)
+{
+	return 0;
+}
+#endif
+
+static irqreturn_t dcc_serial_int_rx(int irq, void *dev_id)
+{
+	struct uart_port *port = dev_id;
+	spin_lock(&port->lock);
+	dcc_serial_rx_chars(port);
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t dcc_serial_int_tx(int irq, void *dev_id)
+{
+	struct uart_port *port = dev_id;
+	spin_lock(&port->lock);
+
+	dcc_serial_tx_chars(port, 64);
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static int dcc_serial_startup(struct uart_port *port)
+{
+	int retval;
+
+	dcc_serial_tx_enable = TX_ON;
+	dcc_serial_rx_enable = RX_ON;
+	/* Allocate the IRQ */
+	retval = request_irq(port->irq, dcc_serial_int_tx, IRQF_DISABLED,
+			     "serial_dcc_serial_tx", port);
+	if (retval)
+		return retval;
+
+	/* Allocate the IRQ */
+	retval = request_irq((int)port->membase, dcc_serial_int_rx, IRQF_DISABLED,
+			     "serial_dcc_serial_rx", port);
+	if (retval)
+		return retval;
+
+	return 0;
+}
+
+static void dcc_serial_shutdown(struct uart_port *port)
+{
+	free_irq(port->irq, port);
+	free_irq((int)port->membase, port);
+}
+#else /* emulation by scheduled work */
+static void dcc_serial_poll(struct work_struct *work);
+static DECLARE_DELAYED_WORK(dcc_serial_poll_task, dcc_serial_poll);
+static struct uart_port dcc_serial_port;
+static int dcc_serial_active;
+
+/* in polling mode, we wait for the next character */
+static int dcc_serial_tx_ready(struct uart_port *port) {
+	while (__dcc_getstatus() & DCC_STATUS_TX) {
+		/* while waiting, we can check rx : it is free */
+		dcc_serial_rx_chars(port);
+		cpu_relax();
+	}
+	return 1;
+}
+
+static void dcc_serial_start_tx(struct uart_port *port)
+{
+	dcc_serial_tx_chars(port, 0xFFFF);
+}
+
+static void dcc_serial_stop_tx(struct uart_port *port)
+{
+}
+
+static void dcc_serial_throttle_rx(struct uart_port *port, int stop)
+{
+}
+
+static void dcc_serial_stop_rx(struct uart_port *port)
+{
+}
+
+/* you can call this on your idle loop instead of sleeping
+ */
+#ifdef CONFIG_SERIAL_DCC_IDLE_POLL
+int dcc_idle(void)
+{
+	struct uart_port *port = &dcc_serial_port;
+	if (dcc_serial_active == 0)
+		return 0;
+
+	spin_lock(&port->lock);
+
+	dcc_serial_rx_chars(port);
+	dcc_serial_tx_chars(port, 64);
+	dcc_serial_rx_chars(port);
+
+	spin_unlock(&port->lock);
+	return 0;
+}
+#endif
+
+/* we poll dcc every jiffies */
+static void dcc_serial_poll(struct work_struct *work)
+{
+	struct uart_port *port = &dcc_serial_port;
+
+	spin_lock(&port->lock);
+
+	dcc_serial_rx_chars(port);
+	dcc_serial_tx_chars(port, 0xFFFF);
+	dcc_serial_rx_chars(port);
+
+	schedule_delayed_work(&dcc_serial_poll_task, 1);
+
+	spin_unlock(&port->lock);
+}
+static int dcc_serial_startup(struct uart_port *port)
+{
+	/* shcedule the polling work */
+	schedule_delayed_work(&dcc_serial_poll_task, 1);
+	dcc_serial_active = 1;
+
+	return 0;
+}
+
+static void dcc_serial_shutdown(struct uart_port *port)
+{
+	cancel_rearming_delayed_work(&dcc_serial_poll_task);
+	dcc_serial_active = 0;
+}
+#endif /* end of DCC_IRQ_USED */
+
+
+static void dcc_serial_putchar(struct uart_port *port, int ch)
+{
+	while (__dcc_getstatus() & DCC_STATUS_TX)
+		cpu_relax();
+	__dcc_putchar((char)(ch & 0xFF));
+}
+
+static void dcc_serial_rx_chars(struct uart_port *port)
+{
+	unsigned char ch;
+	/* max char to send */
+	int count = 64;
+	struct tty_struct *tty = port->info->port.tty;
+
+	/*
+	 * check input.
+	 * checking JTAG flag is better to resolve the status test.
+	 * incount is NOT used for JTAG1 protocol.
+	 */
+
+	while (__dcc_getstatus() & DCC_STATUS_RX && count-- > 0) {
+		/* for JTAG 1 protocol, incount is always 1. */
+		ch = __dcc_getchar();
+
+		tty_insert_flip_char(tty, ch, TTY_NORMAL);
+		port->icount.rx++;
+	}
+	tty_flip_buffer_push(tty);
+}
+
+static void dcc_serial_tx_chars(struct uart_port *port, int max_count)
+{
+	struct circ_buf *xmit = &port->info->xmit;
+
+	if (port->x_char) {
+		dcc_serial_putchar(port, port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+		goto out;
+	}
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		dcc_serial_stop_tx(port);
+		goto out;
+	}
+
+	while (!uart_circ_empty(xmit) && dcc_serial_tx_ready(port)
+			&& max_count-- > 0) {
+		__dcc_putchar(xmit->buf[xmit->tail]);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		port->icount.tx++;
+	}
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
+		uart_write_wakeup(port);
+	}
+	if (uart_circ_empty(xmit)) {
+		dcc_serial_stop_tx(port);
+	}
+
+out:
+	return;
+}
+
+static unsigned int dcc_serial_tx_empty(struct uart_port *port)
+{
+	return (__dcc_getstatus() & DCC_STATUS_TX) ? 0:TIOCSER_TEMT;
+}
+
+static unsigned int dcc_serial_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CTS | TIOCM_DSR | TIOCM_CD;
+}
+
+/* need for throttle/unthrottle */
+static void dcc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	/* throttle clear TIOCM_RTS, unthrottle set it */
+	dcc_serial_throttle_rx(port, !(mctrl & TIOCM_RTS));
+}
+
+static void dcc_serial_set_termios(struct uart_port *port, struct ktermios *termios,
+		   struct ktermios *old)
+{
+	unsigned long flags;
+	unsigned int baud, quot;
+
+	/*
+	 * We don't support parity, stop bits, or anything other
+	 * than 8 bits, so clear these termios flags.
+	 */
+	termios->c_cflag &= ~(CSIZE | CSTOPB | PARENB | PARODD | CREAD);
+	termios->c_cflag |= CS8;
+
+	/*
+	 * We don't appear to support any error conditions either.
+	 */
+	termios->c_iflag &= ~(INPCK | IGNPAR | IGNBRK | BRKINT);
+
+	/*
+	 * Ask the core to calculate the divisor for us.
+	 */
+	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16); 
+	quot = uart_get_divisor(port, baud);
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	uart_update_timeout(port, termios->c_cflag, baud);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char * dcc_serial_type(struct uart_port *port)
+{
+	return port->type == PORT_DCC_JTAG1 ? "DCC" : NULL;
+}
+
+static int dcc_serial_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+/*
+ * Configure/autoconfigure the port.
+ */
+static void dcc_serial_config_port(struct uart_port *port, int flags)
+{
+	if (flags & UART_CONFIG_TYPE) {
+		port->type = PORT_DCC_JTAG1;
+		dcc_serial_request_port(port);
+	}
+}
+
+/*
+ * verify the new serial_struct (for TIOCSSERIAL).
+ */
+static int dcc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
+{
+	int ret = 0;
+	if (ser->type != PORT_UNKNOWN && ser->type != PORT_DCC_JTAG1)
+		ret = -EINVAL;
+	if (ser->irq < 0 || ser->irq >= NR_IRQS)
+		ret = -EINVAL;
+	if (ser->baud_base < 9600)
+		ret = -EINVAL;
+	return ret;
+}
+
+/* dummy operation handlers for uart_ops */
+static void dcc_serial_dummy_ops(struct uart_port *port)
+{
+}
+
+static void dcc_serial_break_ctl(struct uart_port *port, int i)
+{
+}
+
+static struct uart_ops dcc_serial_pops = {
+	.tx_empty	= dcc_serial_tx_empty,
+	.set_mctrl	= dcc_serial_set_mctrl,
+	.get_mctrl	= dcc_serial_get_mctrl,
+	.stop_tx	= dcc_serial_stop_tx,
+	.start_tx	= dcc_serial_start_tx,
+	.stop_rx	= dcc_serial_stop_rx,
+	.enable_ms	= dcc_serial_dummy_ops,
+	.break_ctl	= dcc_serial_break_ctl,
+	.startup	= dcc_serial_startup,
+	.shutdown	= dcc_serial_shutdown,
+	.set_termios	= dcc_serial_set_termios,
+	.type		= dcc_serial_type,
+	.release_port	= dcc_serial_dummy_ops,
+	.request_port	= dcc_serial_request_port,
+	.config_port	= dcc_serial_config_port,
+	.verify_port	= dcc_serial_verify_port,
+};
+
+static struct uart_port dcc_serial_port = {
+	.mapbase	= 0x12345678,		/* for serial_core.c */
+	.iotype		= UPIO_MEM,	
+	.membase	= (char*)IRQ_RX,	/* we need these garbages */
+	.irq		= IRQ_TX,
+	.uartclk	= 14745600,
+	.fifosize	= 0,
+	.ops		= &dcc_serial_pops,
+	.flags		= UPF_BOOT_AUTOCONF,
+	.line		= 0,
+};
+
+#ifdef CONFIG_SERIAL_DCC_CONSOLE
+static void dcc_serial_console_write(struct console *co, const char *s, unsigned int count)
+{
+	uart_console_write(&dcc_serial_port, s, count, dcc_serial_putchar);
+}
+
+static int __init dcc_serial_console_setup(struct console *co, char *options)
+{
+	struct uart_port *port = &dcc_serial_port;
+	int baud = 9600;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(port, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver dcc_serial_reg;
+static struct console dcc_serial_console = {
+	.name		= SERIAL_DCC_NAME,
+	.write		= dcc_serial_console_write,
+	.device		= uart_console_device,
+	.setup		= dcc_serial_console_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+	.data		= &dcc_serial_reg,
+};
+
+static int __init dcc_serial_console_init(void)
+{
+	register_console(&dcc_serial_console);
+	return 0;
+}
+console_initcall(dcc_serial_console_init);
+
+#define DCC_CONSOLE	&dcc_serial_console
+#else
+#define DCC_CONSOLE	NULL
+#endif
+
+static struct uart_driver dcc_serial_reg = {
+	.owner		= THIS_MODULE,
+	.driver_name	= SERIAL_DCC_NAME,
+	.dev_name	= SERIAL_DCC_NAME,
+	.major		= SERIAL_DCC_MAJOR,
+	.minor		= SERIAL_DCC_MINOR,
+	.nr		= UART_NR,
+	.cons		= DCC_CONSOLE,
+};
+
+static int __init dcc_serial_init(void)
+{
+	int ret;
+
+	printk(KERN_INFO "DCC: JTAG1 Serial emulation driver driver $Revision: 1.9 $\n");
+
+	ret = uart_register_driver(&dcc_serial_reg);
+
+	if (ret)
+		return ret;
+
+	uart_add_one_port(&dcc_serial_reg, &dcc_serial_port);
+
+	return 0;
+}
+
+__initcall(dcc_serial_init);
+
+MODULE_DESCRIPTION("DCC(JTAG1) JTAG debugger console emulation driver");
+MODULE_AUTHOR("Hyok S. Choi <hyok.choi@samsung.com>");
+MODULE_SUPPORTED_DEVICE(SERIAL_DCC_NAME);
+MODULE_LICENSE("GPL");