Thank you for your comments.
I'll prepare a revised version ASAP.
Hyok
> -----Original Message-----
> From: Russell King [mailto:[email protected]] On Behalf Of
> Russell King
> Sent: Monday, April 03, 2006 6:11 AM
> To: Hyok S. Choi
> Cc: [email protected]
> Subject: Re: [PATCH 2.6.16-git] [SERIAL] Adds DCC(JTAG)
> serial and the console emulation support
>
> On Wed, Mar 29, 2006 at 04:11:25PM +0900, Hyok S. Choi wrote:
> > diff --git a/drivers/serial/dcc.c b/drivers/serial/dcc.c
>
> Some comments on this driver below.
>
> > new file mode 100644
> > index 0000000..d73ccf6
> > --- /dev/null
> > +++ b/drivers/serial/dcc.c
> > @@ -0,0 +1,550 @@
> > +/*
> > + * linux/drivers/serial/dcc.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
> ([email protected])
> > + * SAMSUNG ELECTRONICS Co.,Ltd.
> > + *
> > + * 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
> > + * Apr-2004 Hyok S. Choi xmit_string_CR added
> > + * Mar-2005 Hyok S. Choi renamed from T32 to DCC
> > + *
> > + */
> > +
> > +#include <linux/config.h>
> > +#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>
> > +
> > +/*
> > + * if real irq interrupt used for receiving character,
> > + * uncomment below line. Unless polling method id used.
> > + */
> > +//#define DCC_IRQ_USED
> > +
> > +#ifndef DCC_IRQ_USED
> > +static struct work_struct dcc_poll_task; static void dcc_poll(void
> > +*data); #endif
> > +
> > +#define UART_NR 1 /* we have only
> one JTAG port */
> > +
> > +#define SERIAL_DCC_NAME "ttyJ"
> > +#define SERIAL_DCC_MAJOR 4
> > +#define SERIAL_DCC_MINOR 64
>
> Is it really a good idea to re-use the same major and minor
> numbers that are used for 8250? What if you want to use DCC
> with a board that has 8250-based serial ports on as well?
>
> > +
> > +static int __inline__ __check_JTAG_RX_FLAG(void)
>
> "static inline int" please.
>
> > +{
> > + int __ret=0;
> > + __asm__ __volatile__(
> > + " mrc p14, 0, %0, c0, c0
> @ read comms control reg\n"
> > + " and %0, %0, #1
> @ jtag read buffer status"
> > + : "=r" (__ret)
> > + );
> > +
> > + /* if __ret == 0 : no input yet
> > + == 1 : a character pending */
>
> Wouldn't it be clearer to have:
>
> static inline u32 read_dcc_status(void)
> {
> u32 status;
>
> asm("mrc p14, 0, %0, c0, c0" : "=r" (status));
>
> return status;
> }
>
> and if you want to check the RX flag in the rest of the code:
>
> if (read_dcc_status() & DCC_STAT_RX) {
> /* do pending character stuff */
> }
>
> ?
>
> > + return __ret;
> > +}
> > +
> > +static void __inline__ __get_JTAG_RX(volatile char *p) {
> > + __asm__ __volatile__(
> > + " mrc p14, 0, r3, c1, c0
> @ read comms data reg to r5\n"
> > + " strb r3, [%0]
> @ str a char"
> > + : /* no output */
> > + : "r" (p)
> > + : "r3", "memory");
> > +}
>
> Ditto comments above. The only use of this I can find is:
>
> __get_JTAG_RX(&ch);
>
> and it's crying out to be:
>
> static inline char dcc_getchar(void)
> {
> char c;
>
> asm("mrc p14, 0, %0, c1, c0" : "=r" (c));
>
> return c;
> }
>
> ...
>
> ch = dcc_getchar();
>
> Also, a write_dcc_char(char c) would be useful.
>
> > +static int __inline__ __check_JTAG_TX_FLAG(void) {
> > + int __ret=0;
> > + __asm__ __volatile__(
> > + " mrc p14, 0, %0, c0, c0
> @ read comms control reg\n"
> > + " and %0, %0, #2
> @ the read buffer status"
> > + : "=r" (__ret)
> > + );
> > +
> > + /* if __ret == 0 : tx is available
> > + == 2 : tx busy */
> > + return __ret;
> > +}
>
> Same comments as for __check_JTAG_RX_FLAG().
>
> > +
> > +void xmit_string(char *p, int len)
> > +{
> > +#ifndef CONFIG_JTAG_DCC_OUTPUT_DISABLE
> > + /*
> > + r0 = string ; string address
> > + r1 = 2 ; state check bit (write)
> > + r4 = *string ; character
> > + r7 = 0 ; count
> > + */
> > + __asm__ __volatile__(
> > + " mov r7, #0\n"
> > + "1: mrc p14, 0, r3, c0, c0 @ read
> comms control reg\n"
> > + " and r3, r3, #2 @ the
> write buffer status\n"
> > + " cmp r3, #2 @ is it
> available?\n"
> > + " beq 1b @ is
> not, wait till then\n"
> > + " ldrb r4, [%0] @ load a char\n"
> > + " mcr p14, 0, r4, c1, c0 @ write it\n"
> > + " add %0, %0, #1 @ str
> address increase one\n"
> > + " add r7, r7, #1 @ count
> increase\n"
> > + " cmp r7, %1 @
> compare with str length\n"
> > + " bne 1b @ if it
> is not yet, loop"
> > + : /* no output register */
> > + : "r" (p), "r" (len)
> > + : "r7", "r3", "r4");
> > +#endif
> > +}
>
> Does this really need to be written all in assembly?
> Shouldn't it be declared static?
>
> Wouldn't something like the following be better?
>
> static void dcc_putchar(struct uart_port *port, char c) {
> while (read_dcc_status() & DCC_STAT_TX_FULL)
> cpu_relax();
> write_dcc_char(c);
> }
>
> static void xmit_string(struct uart_port *port, const char
> *p, int len) {
> for (; len; len--, p++)
> dcc_putchar(port, *p);
> }
>
> > +
> > +void xmit_string_CR(char *p, int len) { #ifndef
> > +CONFIG_JTAG_DCC_OUTPUT_DISABLE
> > + /*
> > + r0 = string ; string address
> > + r1 = 2 ; state check bit (write)
> > + r4 = *string ; character
> > + r7 = 0 ; count
> > + */
> > + __asm__ __volatile__(
> > + " mov r7, #0\n"
> > + " ldrb r4, [%0] @ load a char\n"
> > + "1: mrc p14, 0, r3, c0, c0 @ read
> comms control reg\n"
> > + " and r3, r3, #2 @ the
> write buffer status\n"
> > + " cmp r3, #2 @ is it
> available?\n"
> > + " beq 1b @ is
> not, wait till then\n"
> > + " mcr p14, 0, r4, c1, c0 @ write it\n"
> > + " cmp r4, #0x0a @ is it LF?\n"
> > + " bne 2f @ if it
> is not, continue\n"
> > + " mov r4, #0x0d @ set the CR\n"
> > + " b 1b @ loop
> for writing CR\n"
> > + "2: ldrb r4, [%0, #1]! @ load a char\n"
> > + " add r7, r7, #1 @ count
> increase\n"
> > + " cmp r7, %1 @
> compare with str length\n"
> > + " bne 1b @ if it
> is not yet, loop"
> > + : /* no output register */
> > + : "r" (p), "r" (len)
> > + : "r7", "r3", "r4");
> > +#endif
> > +}
>
> No need - use uart_console_write() for this, which will do
> the LF -> CRLF translation for you. All you need to do is to
> supply a function to do the individual character based
> writing. You can pass dcc_putchar() as the putchar function
> (which is why I wrote xmit_string that way
> above.)
>
> > +
> > +
> > +static void
> > +dcc_stop_tx(struct uart_port *port)
> > +{
> > +}
> > +
> > +static inline void
> > +dcc_transmit_buffer(struct uart_port *port) {
> > + struct circ_buf *xmit = &port->info->xmit;
> > +
>
> Blank line not required.
>
> > + int pendings = uart_circ_chars_pending(xmit);
> > +
> > + if(pendings + xmit->tail > UART_XMIT_SIZE)
> > + {
>
> Interesting indentation style mix.
>
> > + xmit_string(&(xmit->buf[xmit->tail]),
> UART_XMIT_SIZE - xmit->tail);
> > + xmit_string(&(xmit->buf[0]), xmit->head);
> > + } else
> > + xmit_string(&(xmit->buf[xmit->tail]), pendings);
> > +
> > + xmit->tail = (xmit->tail + pendings) & (UART_XMIT_SIZE-1);
> > + port->icount.tx += pendings;
>
> Tabs vs spaces indentation. Please use a consistent
> indentation style.
>
> > +
> > + if (uart_circ_empty(xmit))
> > + dcc_stop_tx(port);
>
> dcc_stop_tx itself is empty, so this doesn't serve a useful purpose.
>
> > +}
> > +
> > +static inline void
> > +dcc_transmit_x_char(struct uart_port *port) {
> > + xmit_string(&port->x_char, 1);
>
> Another potential user of dcc_putchar().
>
> > + port->icount.tx++;
> > + port->x_char = 0;
> > +}
> > +
> > +static void
> > +dcc_start_tx(struct uart_port *port)
> > +{
> > + dcc_transmit_buffer(port);
> > +}
> > +
> > +static void
> > +dcc_stop_rx(struct uart_port *port)
> > +{
> > +}
> > +
> > +static void
> > +dcc_enable_ms(struct uart_port *port) { }
>
> Maybe call all the empty functions which take just a uart_port
>
> static void dcc_dummy(struct uart_port *port) { }
>
> and use it in the uart_ops structure as appropriate.
>
> > +
> > +static inline void
> > +dcc_rx_chars(struct uart_port *port)
> > +{
> > + unsigned char ch;
> > + struct tty_struct *tty = port->info->tty;
> > +
> > + /*
> > + * check input.
> > + * checking JTAG flag is better to resolve the status test.
> > + * incount is NOT used for JTAG1 protocol.
> > + */
> > +
> > + if (__check_JTAG_RX_FLAG())
> > + /* if __ret == 0 : no input yet
> > + == 1 : a character pending */
>
> if (read_dcc_status() & DCC_STAT_RX) {
>
> > + {
> > + /* for JTAG 1 protocol, incount is always 1. */
> > + __get_JTAG_RX(&ch);
>
> ch = dcc_getchar();
>
> > +
> > + if (tty) {
> > + tty_insert_flip_char(tty, ch, TTY_NORMAL);
> > + port->icount.rx++;
> > + tty_flip_buffer_push(tty);
> > + }
> > + }
> > +}
> > +
> > +static inline void
> > +dcc_overrun_chars(struct uart_port *port) {
> > + port->icount.overrun++;
> > +}
> > +
> > +static inline void
> > +dcc_tx_chars(struct uart_port *port)
> > +{
> > + struct circ_buf *xmit = &port->info->xmit;
> > +
> > + if (port->x_char) {
> > + dcc_transmit_x_char(port);
> > + return;
> > + }
> > +
> > + if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
> > + dcc_stop_tx(port);
> > + return;
> > + }
>
> If we're using interrupt mode, given that dcc_stop_tx() is
> empty, how do we stop spinning on the transmit interrupt?
>
> > +
> > + dcc_transmit_buffer(port);
> > +
> > + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> > + uart_write_wakeup(port);
> > +}
> > +
> > +#ifdef DCC_IRQ_USED /* real IRQ used */ static irqreturn_t
> > +dcc_int(int irq, void *dev_id, struct pt_regs *regs) {
> > + struct uart_port *port = dev_id;
> > + int handled = 0;
> > +
> > + spin_lock(&port->lock);
> > +
> > + dcc_rx_chars(port);
> > + dcc_tx_chars(port);
> > +
> > + handled = 1;
> > + spin_unlock(&port->lock);
> > +
> > + return IRQ_RETVAL(handled);
> > +}
> > +
> > +#else /* emulation by scheduled work */ static void dcc_poll(void
> > +*data) {
> > + struct uart_port *port = data;
> > +
> > + spin_lock(&port->lock);
> > +
> > + dcc_rx_chars(port);
> > + dcc_tx_chars(port);
> > +
> > + schedule_delayed_work(&dcc_poll_task, 1);
> > +
> > + spin_unlock(&port->lock);
> > +
> > +}
> > +#endif /* end of DCC_IRQ_USED */
> > +
> > +static unsigned int
> > +dcc_tx_empty(struct uart_port *port)
> > +{
> > + return TIOCSER_TEMT;
> > +}
> > +
> > +static unsigned int
> > +dcc_get_mctrl(struct uart_port *port) {
> > + return 0;
>
> Should return TIOCM_CTS | TIOCM_DSR | TIOCM_CD if control
> lines aren't implemented.
>
> > +}
> > +
> > +static void
> > +dcc_set_mctrl(struct uart_port *port, unsigned int mctrl) { }
> > +
> > +static void
> > +dcc_break_ctl(struct uart_port *port, int break_state) { }
> > +
> > +static int dcc_startup(struct uart_port *port) { #ifdef
> DCC_IRQ_USED
> > +/* real IRQ used */
> > + int retval;
> > +
> > + /* 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);
> > + schedule_delayed_work(&dcc_poll_task, 1); #endif
> > +
> > + return 0;
> > +}
> > +
> > +static void dcc_shutdown(struct uart_port *port) {
>
> Shouldn't the dcc_poll_task be stopped somehow here?
>
> > +}
> > +
> > +static void
> > +dcc_set_termios(struct uart_port *port, struct termios *termios,
> > + struct termios *old)
> > +{
> > +#ifdef DCC_IRQ_USED
> > + unsigned long flags;
> > +#endif
> > + 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);
> > +
> > +#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 }
> > +
> > +static const char *dcc_type(struct uart_port *port) {
> > + return port->type == PORT_DCC_JTAG1 ? "DCC" : NULL; }
> > +
> > +static void dcc_release_port(struct uart_port *port) { }
> > +
> > +static int dcc_request_port(struct uart_port *port) {
> > + return 0;
> > +}
> > +
> > +/*
> > + * Configure/autoconfigure the port.
> > + */
> > +static void dcc_config_port(struct uart_port *port, int flags) {
> > + if (flags & UART_CONFIG_TYPE) {
> > + port->type = PORT_DCC_JTAG1;
> > + dcc_request_port(port);
> > + }
> > +}
> > +
> > +/*
> > + * verify the new serial_struct (for TIOCSSERIAL).
> > + */
> > +static int dcc_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;
>
> Weirdo indentation style strikes again.
>
> > +}
> > +
> > +static struct uart_ops dcc_pops = {
> > + .tx_empty = dcc_tx_empty,
> > + .set_mctrl = dcc_set_mctrl,
> > + .get_mctrl = dcc_get_mctrl,
> > + .stop_tx = dcc_stop_tx,
> > + .start_tx = dcc_start_tx,
> > + .stop_rx = dcc_stop_rx,
> > + .enable_ms = dcc_enable_ms,
> > + .break_ctl = dcc_break_ctl,
> > + .startup = dcc_startup,
> > + .shutdown = dcc_shutdown,
> > + .set_termios = dcc_set_termios,
> > + .type = dcc_type,
> > + .release_port = dcc_release_port,
> > + .request_port = dcc_request_port,
> > + .config_port = dcc_config_port,
> > + .verify_port = dcc_verify_port,
> > +};
> > +
> > +static struct uart_port dcc_ports[UART_NR] = {
>
> If there's only one port, this array isn't required.
>
> > + {
> > + .membase = (char*)0x12345678, /* we
> need these garbages */
> > + .mapbase = 0x12345678, /* for
> serial_core.c */
> > + .iotype = SERIAL_IO_MEM,
>
> .iotype should be UPIO_xxx not SERIAL_IO_xxx.
>
> > +#ifdef DCC_IRQ_USED
> > + .irq = INT_N_EXT0,
> > +#else
> > + .irq = 0,
> > +#endif
> > + .uartclk = 14745600,
> > + .fifosize = 0,
> > + .ops = &dcc_pops,
> > + .flags = ASYNC_BOOT_AUTOCONF,
>
> .flags should be UPF_xxx not ASYNC_xxx.
>
> > + .line = 0,
> > + },
> > +};
> > +
> > +
> > +#ifdef CONFIG_SERIAL_DCC_CONSOLE
> > +
> > +static void
> > +dcc_console_write(struct console *co, const char *s, unsigned int
> > +count) {
> > + xmit_string_CR((char*)s, count);
> > +}
> > +
> > +/*
> > + * Read the current UART setup.
> > + */
> > +static void __init
> > +dcc_console_get_options(struct uart_port *port, int *baud, int
> > +*parity, int
> > *bits)
> > +{
> > + *baud = 9600;
> > + *parity = 'n';
> > + *bits = 8;
> > +}
>
> Unnecessary function.
>
> > +
> > +static int __init
> > +dcc_console_setup(struct console *co, char *options) {
> > + struct uart_port *port;
> > + int baud = 9600;
> > + int bits = 8;
> > + int parity = 'n';
> > + int flow = 'n';
> > +
> > + if (co->index >= UART_NR)
> > + co->index = 0;
> > + port = &dcc_ports[co->index];
>
> If you're not likely to have more than one port, this doesn't
> make sense.
>
> > +
> > + if (options)
> > + uart_parse_options(options, &baud, &parity,
> &bits, &flow);
> > + else
> > + dcc_console_get_options(port, &baud, &parity, &bits);
> > +
> > + return uart_set_options(port, co, baud, parity, bits, flow); }
> > +
> > +extern struct uart_driver dcc_reg;
> > +static struct console dcc_console = {
> > + .name = SERIAL_DCC_NAME,
> > + .write = dcc_console_write,
> > + .device = uart_console_device,
> > + .setup = dcc_console_setup,
> > + .flags = CON_PRINTBUFFER,
> > + .index = -1,
> > + .data = &dcc_reg,
> > +};
> > +
> > +static int __init dcc_console_init(void) {
> > + register_console(&dcc_console);
> > + return 0;
> > +}
> > +console_initcall(dcc_console_init);
> > +
> > +#define DCC_CONSOLE &dcc_console
> > +#else
> > +#define DCC_CONSOLE NULL
> > +#endif
> > +
> > +static struct uart_driver dcc_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_init(void)
> > +{
> > + int i, ret = 0;
> > +
> > + printk(KERN_INFO "DCC: JTAG1 Serial emulation driver driver
> > +$Revision: 1.1
> > $\n");
> > +
> > + ret = uart_register_driver(&dcc_reg);
> > +
> > + if (ret)
> > + return ret;
> > +
> > + for (i = 0; i < UART_NR; i++)
> > + uart_add_one_port(&dcc_reg, &dcc_ports[i]);
>
> Are you likely to have more than one port? Does this loop
> really make sense?
>
> > +
> > + return ret;
> > +}
> > +
> > +__initcall(dcc_init);
> > +
> > +MODULE_DESCRIPTION("DCC(JTAG1) JTAG debugger console emulation
> > +driver"); MODULE_AUTHOR("Hyok S. Choi <[email protected]>");
> > +MODULE_SUPPORTED_DEVICE("ttyJ"); MODULE_LICENSE("GPL");
>
> --
> Russell King
> Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
> maintainer of: 2.6 Serial core
>
>
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