Messages in this thread | | | Date | Sun, 2 Apr 2006 22:11:18 +0100 | From | Russell King <> | Subject | Re: [PATCH 2.6.16-git] [SERIAL] Adds DCC(JTAG) serial and the console emulation support |
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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 (hyok.choi@samsung.com) > + * 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 <hyok.choi@samsung.com>"); > +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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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