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![Mike Frysinger](/assets/img/avatar_default.png)
The Blackfin JTAG has the ability to pass data via a back-channel without halting the processor. Utilize that channel to emulate a console. Signed-off-by: Mike Frysinger <vapier@gentoo.org>
126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
/*
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* jtag-console.c - console driver over Blackfin JTAG
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*
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* Copyright (c) 2008 Analog Devices Inc.
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*
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* Licensed under the GPL-2 or later.
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*/
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#include <common.h>
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#include <devices.h>
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#include <asm/blackfin.h>
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#ifndef CONFIG_JTAG_CONSOLE_TIMEOUT
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# define CONFIG_JTAG_CONSOLE_TIMEOUT 100
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#endif
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/* The Blackfin tends to be much much faster than the JTAG hardware. */
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static void jtag_write_emudat(uint32_t emudat)
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{
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static bool overflowed = false;
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ulong timeout = get_timer(0) + CONFIG_JTAG_CONSOLE_TIMEOUT;
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while (bfin_read_DBGSTAT() & 0x1) {
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if (overflowed)
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return;
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if (timeout < get_timer(0))
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overflowed = true;
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}
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overflowed = false;
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__asm__ __volatile__("emudat = %0;" : : "d"(emudat));
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}
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/* Transmit a buffer. The format is:
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* [32bit length][actual data]
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*/
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static void jtag_send(const char *c, uint32_t len)
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{
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uint32_t i;
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if (len == 0)
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return;
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/* First send the length */
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jtag_write_emudat(len);
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/* Then send the data */
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for (i = 0; i < len; i += 4)
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jtag_write_emudat((c[i] << 0) | (c[i+1] << 8) | (c[i+2] << 16) | (c[i+3] << 24));
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}
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static void jtag_putc(const char c)
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{
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jtag_send(&c, 1);
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}
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static void jtag_puts(const char *s)
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{
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jtag_send(s, strlen(s));
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}
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static int jtag_tstc(void)
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{
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return (bfin_read_DBGSTAT() & 0x2);
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}
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/* Receive a buffer. The format is:
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* [32bit length][actual data]
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*/
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static size_t inbound_len;
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static int leftovers_len;
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static uint32_t leftovers;
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static int jtag_getc(void)
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{
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int ret;
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uint32_t emudat;
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/* see if any data is left over */
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if (leftovers_len) {
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--leftovers_len;
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ret = leftovers & 0xff;
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leftovers >>= 8;
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return ret;
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}
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/* wait for new data ! */
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while (!jtag_tstc())
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continue;
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__asm__("%0 = emudat;" : "=d"(emudat));
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if (inbound_len == 0) {
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/* grab the length */
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inbound_len = emudat;
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} else {
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/* store the bytes */
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leftovers_len = min(4, inbound_len);
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inbound_len -= leftovers_len;
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leftovers = emudat;
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}
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return jtag_getc();
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}
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int drv_jtag_console_init(void)
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{
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device_t dev;
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int ret;
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memset(&dev, 0x00, sizeof(dev));
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strcpy(dev.name, "jtag");
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dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
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dev.putc = jtag_putc;
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dev.puts = jtag_puts;
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dev.tstc = jtag_tstc;
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dev.getc = jtag_getc;
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ret = device_register(&dev);
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return (ret == 0 ? 1 : ret);
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}
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#ifdef CONFIG_UART_CONSOLE_IS_JTAG
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/* Since the JTAG is always available (at power on), allow it to fake a UART */
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void serial_set_baud(uint32_t baud) {}
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void serial_setbrg(void) {}
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int serial_init(void) { return 0; }
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void serial_putc(const char c) __attribute__((alias("jtag_putc")));
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void serial_puts(const char *s) __attribute__((alias("jtag_puts")));
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int serial_tstc(void) __attribute__((alias("jtag_tstc")));
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int serial_getc(void) __attribute__((alias("jtag_getc")));
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#endif
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