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

From: matthieu castet
Date: Fri Oct 08 2010 - 16:40:34 EST

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In reply to: Daniel Walker: "Re: [PATCH] serial: DCC(JTAG) serial and console emulation support"
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Daniel Walker a Ãcrit :

On Fri, 2010-10-08 at 21:34 +0200, matthieu castet wrote:
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).

Do you use the CONFIG_SERIAL_DCC_STDSERIAL feature?

No, I never used it

Matthieu

PS : I attached a diff against the original version. Looking at it, I think the really interesting stuff is
the dcc_idle that should called in a thread with low priority. The reactivity of the workqueue was very bad IIRC.

Irq stuff is only supported by few cpu, so I am not sure it worth to merge it. --- drivers/serial/dcc.c 2010-10-08 22:21:57.000000000 +0200
+++ drivers/parrot/serial/dcc.c 2010-10-08 22:24:07.000000000 +0200
@@ -6,6 +6,7 @@
* DCC(JTAG1) protocol version for JTAG ICE/ICD Debuggers:
* Copyright (C) 2003, 2004, 2005 Hyok S. Choi (hyok.choi@xxxxxxxxxxx)
* SAMSUNG ELECTRONICS Co.,Ltd.
+ * Copyright (C) 2008 Parrot SA by matthieu.castet@xxxxxxxxxx
*
* 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
@@ -19,7 +20,6 @@
*
*/

-#include <linux/config.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
@@ -35,21 +35,21 @@

#include <linux/serial_core.h>

-/*
- * if real irq interrupt used for receiving character,
- * uncomment below line and modify the DCC_IRQ to correct one.
- * Unless polling method id used.
- */
-//#define DCC_IRQ_USED
-//#define DCC_IRQ (INT_N_EXT0)
+/* 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

-#ifndef DCC_IRQ_USED
-#define DCC_POLL_RUN 0
-#define DCC_POLL_STOP 1
-#define DCC_POLL_STOPPED 2
-static struct work_struct dcc_poll_task;
-static void dcc_poll(void *data);
-static int dcc_poll_state = DCC_POLL_STOPPED;
+#warning polling mode
#endif

#define UART_NR 1 /* we have only one JTAG port */
@@ -57,240 +57,359 @@
#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_MINOR (64 + 64)
+#define SERIAL_DCC_MAJOR 204
+#define SERIAL_DCC_MINOR 186
#endif
-#define SERIAL_DCC_MAJOR TTY_MAJOR

/* DCC Status Bits */
#define DCC_STATUS_RX (1 << 0)
#define DCC_STATUS_TX (1 << 1)

+/* end of JTAG1 dependencies */

-static void
-dcc_putchar(struct uart_port *port, int ch)
-{
- while (__dcc_getstatus() & DCC_STATUS_TX)
- cpu_relax();
- __dcc_putchar((char)(ch & 0xFF));
+static void dcc_tx_chars(struct uart_port *port, int max_count);
+static void dcc_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_tx_ready(port) \
+ ((__dcc_getstatus() & DCC_STATUS_TX) == 0)
+
+enum {
+ TX_OFF,
+ TX_ON,
+};
+static int dcc_tx_enable;
+enum {
+ RX_OFF,
+ RX_ON,
+ RX_PAUSE,
+};
+static int dcc_rx_enable;
+/* port locked, interrupts locally disabled */
+static void dcc_start_tx(struct uart_port *port)
+{
+ if (dcc_tx_enable == TX_OFF) {
+ enable_irq(port->irq);
+ dcc_tx_enable = TX_ON;
+ }
}

-static inline void
-xmit_string(struct uart_port *port, char *p, int len)
+/* port locked, interrupts locally disabled */
+static void dcc_stop_tx(struct uart_port *port)
{
- for ( ; len; len--, p++)
- dcc_putchar(port, *p);
+ if (dcc_tx_enable == TX_ON) {
+ disable_irq(port->irq);
+ dcc_tx_enable = TX_OFF;
+ }
}

-static inline void
-dcc_transmit_buffer(struct uart_port *port)
+/* port locked, interrupts locally disabled */
+static void dcc_stop_rx(struct uart_port *port)
{
- struct circ_buf *xmit = &port->info->xmit;
- int pendings = uart_circ_chars_pending(xmit);
+ if (dcc_rx_enable == RX_ON) {
+ disable_irq((int)port->membase);
+ }
+ dcc_rx_enable = RX_OFF;
+}

- if(pendings + xmit->tail > UART_XMIT_SIZE)
- {
- xmit_string(port, &(xmit->buf[xmit->tail]),
- UART_XMIT_SIZE - xmit->tail);
- xmit_string(port, &(xmit->buf[0]), xmit->head);
- } else
- xmit_string(port, &(xmit->buf[xmit->tail]), pendings);
+/* port locked, interrupts locally disabled */
+static void dcc_throttle_rx(struct uart_port *port, int stop)
+{
+ if (stop && dcc_rx_enable == RX_ON) {
+ disable_irq((int)port->membase);
+ dcc_rx_enable = RX_PAUSE;
+ }
+ else if (stop == 0 && dcc_rx_enable == RX_PAUSE) {
+ enable_irq((int)port->membase);
+ dcc_rx_enable = RX_ON;
+ }
+}

- xmit->tail = (xmit->tail + pendings) & (UART_XMIT_SIZE-1);
- port->icount.tx += pendings;
+#infdef CONFIG_SERIAL_DCC_IDLE_POLL
+int dcc_idle(void)
+{
+ return 0;
+}
+#endif

-static inline void
-dcc_transmit_x_char(struct uart_port *port)
+static irqreturn_t dcc_int_rx(int irq, void *dev_id)
{
- dcc_putchar(port, port->x_char);
- port->icount.tx++;
- port->x_char = 0;
+ struct uart_port *port = dev_id;
+ spin_lock(&port->lock);
+ dcc_rx_chars(port);
+ spin_unlock(&port->lock);
+
+ return IRQ_HANDLED;
}

-static void
-dcc_start_tx(struct uart_port *port)
+static irqreturn_t dcc_int_tx(int irq, void *dev_id)
{
- dcc_transmit_buffer(port);
+ struct uart_port *port = dev_id;
+ spin_lock(&port->lock);
+
+ dcc_tx_chars(port, 64);
+ spin_unlock(&port->lock);
+
+ return IRQ_HANDLED;
}

-static inline void
-dcc_rx_chars(struct uart_port *port)
+static int dcc_startup(struct uart_port *port)
{
- unsigned char ch;
- struct tty_struct *tty = port->info->tty;
+ int retval;

- /*
- * check input.
- * checking JTAG flag is better to resolve the status test.
- * incount is NOT used for JTAG1 protocol.
- */
+ dcc_tx_enable = TX_ON;
+ dcc_rx_enable = RX_ON;
+ /* Allocate the IRQ */
+ retval = request_irq(port->irq, dcc_int_tx, IRQF_DISABLED,
+ "serial_dcc_tx", port);
+ if (retval)
+ return retval;

- if (__dcc_getstatus() & DCC_STATUS_RX)
- {
- /* for JTAG 1 protocol, incount is always 1. */
- ch = __dcc_getchar();
+ /* Allocate the IRQ */
+ retval = request_irq((int)port->membase, dcc_int_rx, IRQF_DISABLED,
+ "serial_dcc_rx", port);
+ if (retval)
+ return retval;

- if (tty) {
- tty_insert_flip_char(tty, ch, TTY_NORMAL);
- port->icount.rx++;
- tty_flip_buffer_push(tty);
- }
- }
+ return 0;
}

-static inline void
-dcc_overrun_chars(struct uart_port *port)
+static void dcc_shutdown(struct uart_port *port)
{
- port->icount.overrun++;
+ free_irq(port->irq, port);
+ free_irq((int)port->membase, port);
+}
+#else /* emulation by scheduled work */
+static void dcc_poll(struct work_struct *work);
+static DECLARE_DELAYED_WORK(dcc_poll_task, dcc_poll);
+static struct uart_port dcc_port;
+static int dcc_active;
+
+/* in polling mode, we wait for the next character */
+static int dcc_tx_ready(struct uart_port *port) {
+ while (__dcc_getstatus() & DCC_STATUS_TX) {
+ /* while waiting, we can check rx : it is free */
+ dcc_rx_chars(port);
+ cpu_relax();
+ }
+ return 1;
}

-static inline void
-dcc_tx_chars(struct uart_port *port)
+static void dcc_start_tx(struct uart_port *port)
{
- struct circ_buf *xmit = &port->info->xmit;
-
- if (port->x_char) {
- dcc_transmit_x_char(port);
- return;
- }
+ dcc_tx_chars(port, 0xFFFF);
+}

- if (uart_circ_empty(xmit) || uart_tx_stopped(port))
- return;
+static void dcc_stop_tx(struct uart_port *port)
+{
+}

- dcc_transmit_buffer(port);
+static void dcc_throttle_rx(struct uart_port *port, int stop)
+{
+}

- if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
- uart_write_wakeup(port);
+static void dcc_stop_rx(struct uart_port *port)
+{
}

-#ifdef DCC_IRQ_USED /* real IRQ used */
-static irqreturn_t
-dcc_int(int irq, void *dev_id, struct pt_regs *regs)
+/* 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 = dev_id;
- int handled = 0;
+ struct uart_port *port = &dcc_port;
+ if (dcc_active == 0)
+ return 0;

spin_lock(&port->lock);

dcc_rx_chars(port);
- dcc_tx_chars(port);
+ dcc_tx_chars(port, 64);
+ dcc_rx_chars(port);

- handled = 1;
spin_unlock(&port->lock);
-
- return IRQ_RETVAL(handled);
+ return 0;
}
-#else /* emulation by scheduled work */
-static void
-dcc_poll(void *data)
+#endif
+
+/* we poll dcc every jiffies */
+static void dcc_poll(struct work_struct *work)
{
- struct uart_port *port = data;
+ struct uart_port *port = &dcc_port;

spin_lock(&port->lock);

- if (dcc_poll_state != DCC_POLL_RUN) {
- dcc_poll_state = DCC_POLL_STOPPED;
- goto dcc_poll_stop;
- }
-
dcc_rx_chars(port);
- dcc_tx_chars(port);
+ dcc_tx_chars(port, 0xFFFF);
+ dcc_rx_chars(port);

schedule_delayed_work(&dcc_poll_task, 1);

-dcc_poll_stop:
spin_unlock(&port->lock);
}
+static int dcc_startup(struct uart_port *port)
+{
+ /* shcedule the polling work */
+ schedule_delayed_work(&dcc_poll_task, 1);
+ dcc_active = 1;
+
+ return 0;
+}
+
+static void dcc_shutdown(struct uart_port *port)
+{
+ cancel_rearming_delayed_work(&dcc_poll_task);
+ dcc_active = 0;
+}
#endif /* end of DCC_IRQ_USED */

-static unsigned int
-dcc_tx_empty(struct uart_port *port)
+
+static void dcc_putchar(struct uart_port *port, int ch)
{
- return TIOCSER_TEMT;
+ while (__dcc_getstatus() & DCC_STATUS_TX)
+ cpu_relax();
+ __dcc_putchar((char)(ch & 0xFF));
}

-static unsigned int
-dcc_get_mctrl(struct uart_port *port)
+static void dcc_rx_chars(struct uart_port *port)
{
- return TIOCM_CTS | TIOCM_DSR | TIOCM_CD;
+ 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 int
-dcc_startup(struct uart_port *port)
+static void dcc_tx_chars(struct uart_port *port, int max_count)
{
-#ifdef DCC_IRQ_USED /* real IRQ used */
- int retval;
+ struct circ_buf *xmit = &port->info->xmit;

- /* Allocate the IRQ */
- retval = request_irq(port->irq, dcc_int, SA_INTERRUPT,
- "serial_dcc", port);
- if (retval)
- return retval;
-#else /* emulation */
- /* Initialize the work, and shcedule it. */
- INIT_WORK(&dcc_poll_task, dcc_poll, port);
- spin_lock(&port->lock);
- if (dcc_poll_state != DCC_POLL_RUN)
- dcc_poll_state = DCC_POLL_RUN;
- schedule_delayed_work(&dcc_poll_task, 1);
- spin_unlock(&port->lock);
-#endif
+ if (port->x_char) {
+ dcc_putchar(port, port->x_char);
+ port->icount.tx++;
+ port->x_char = 0;
+ goto out;
+ }
+ if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+ dcc_stop_tx(port);
+ goto out;
+ }

- return 0;
+ while (!uart_circ_empty(xmit) && dcc_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_stop_tx(port);
+ }
+
+out:
+ return;
}

-static void
-dcc_shutdown(struct uart_port *port)
+static unsigned int dcc_tx_empty(struct uart_port *port)
{
-#ifdef DCC_IRQ_USED /* real IRQ used */
- free_irq(port->irq, port);
-#else
- spin_lock(&port->lock);
- dcc_poll_state = DCC_POLL_STOP;
- spin_unlock(&port->lock);
-#endif
+ return (__dcc_getstatus() & DCC_STATUS_TX) ? 0:TIOCSER_TEMT;
+}
+
+static unsigned int dcc_get_mctrl(struct uart_port *port)
+{
+ return TIOCM_CTS | TIOCM_DSR | TIOCM_CD;
+}
+
+/* need for throttle/unthrottle */
+static void dcc_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+ /* throttle clear TIOCM_RTS, unthrottle set it */
+ dcc_throttle_rx(port, !(mctrl & TIOCM_RTS));
}

-static void
-dcc_set_termios(struct uart_port *port, struct termios *termios,
- struct termios *old)
+static void dcc_set_termios(struct uart_port *port, struct ktermios *termios,
+ struct ktermios *old)
{
-#ifdef DCC_IRQ_USED
unsigned long flags;
-#endif
unsigned int baud, quot;

/*
@@ -311,25 +430,19 @@
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
quot = uart_get_divisor(port, baud);

-#ifdef DCC_IRQ_USED
spin_lock_irqsave(&port->lock, flags);
-#endif

uart_update_timeout(port, termios->c_cflag, baud);

-#ifdef DCC_IRQ_USED
spin_unlock_irqrestore(&port->lock, flags);
-#endif
}

@@ -363,28 +474,23 @@
}

/* dummy operation handlers for uart_ops */
-static void
-dcc_dummy_ops(struct uart_port *port)
+static void dcc_dummy_ops(struct uart_port *port)
{
}
-static void
-dcc_dummy_ops_ui(struct uart_port *port, unsigned int ui)
-{
-}
-static void
-dcc_dummy_ops_i(struct uart_port *port, int i)
+
+static void dcc_break_ctl(struct uart_port *port, int i)
{
}

static struct uart_ops dcc_pops = {
.tx_empty = dcc_tx_empty,
- .set_mctrl = dcc_dummy_ops_ui,
+ .set_mctrl = dcc_set_mctrl,
.get_mctrl = dcc_get_mctrl,
- .stop_tx = dcc_dummy_ops,
+ .stop_tx = dcc_stop_tx,
.start_tx = dcc_start_tx,
- .stop_rx = dcc_dummy_ops,
+ .stop_rx = dcc_stop_rx,
.enable_ms = dcc_dummy_ops,
- .break_ctl = dcc_dummy_ops_i,
+ .break_ctl = dcc_break_ctl,
.startup = dcc_startup,
.shutdown = dcc_shutdown,
.set_termios = dcc_set_termios,
@@ -396,14 +502,10 @@
};

static struct uart_port dcc_port = {
- .membase = (char*)0x12345678, /* we need these garbages */
.mapbase = 0x12345678, /* for serial_core.c */
.iotype = UPIO_MEM,
-#ifdef DCC_IRQ_USED
- .irq = DCC_IRQ,
-#else
- .irq = 0,
-#endif
+ .membase = (char*)IRQ_RX, /* we need these garbages */
+ .irq = IRQ_TX,
.uartclk = 14745600,
.fifosize = 0,
.ops = &dcc_pops,

Next message: Greg KH: "Re: [RFD] Device Renaming Mechanism"
Previous message: Nikhil Rao: "Re: [PATCH 0/3][RFC] Improve load balancing when tasks have largeweight differential"
In reply to: Daniel Walker: "Re: [PATCH] serial: DCC(JTAG) serial and console emulation support"
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