Digilent Embedded Linux User Manual
Page 21
Using Zynq with Linux
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GDB will show where the kernel is hanging up. Example 21 shows that the kernel hangs at function
xuart_console_wait_tx. You can back trace the function call procedure with the command
backtrace.
Example 21.
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0xc01ea030 in xuartps_console_wait_tx (port=0xc0b84d78) at
drivers/tty/serial/xilinx_uartps.c:944
944
while ((xuartps_readl(XUARTPS_SR_OFFSET) & XUARTPS_SR_TXEMPTY)
(gdb) backtrace
#0 0xc01ea030 in xuartps_console_wait_tx (port=0xc0b84d78) at
drivers/tty/serial/xilinx_uartps.c:944
#1 0xc01ea05c in xuartps_console_putchar (port=0xc0b84d78, ch=91) at
drivers/tty/serial/xilinx_uartps.c:958
#2 0xc01e6e4c in uart_console_write (port=0xc0b84d78, s=
drivers/tty/serial/serial_core.c:1680
#3 0xc01ea1d8 in xuartps_console_write (co=
s=0xc0731df9 "[ 2.140000] usb 1-1.2: new low-speed USB device number 3
using xusbps-ehci\n WARNING: at arch/arm/mm/dma-mapping.c:198
consistent_init+0x78/0x10c()\n<4>[ 0.430000] Modules linked in:\n<4>[
0.430"..., count=78)
at drivers/tty/serial/xilinx_uartps.c:985
#4 0xc00226bc in __call_console_drivers (start=20840, end=20918) at
kernel/printk.c:520
#5 0xc0022760 in _call_console_drivers (start=
end=20918, msg_log_level=
#6 0xc0022f70 in call_console_drivers () at kernel/printk.c:654
#7 console_unlock () at kernel/printk.c:1275
#8 0xc0023564 in vprintk (fmt=
kernel/printk.c:964
#9 0xc039d8bc in printk (fmt=0xc04a7dad "%s%s %s: %pV") at
kernel/printk.c:756
#10 0xc020b5b8 in __dev_printk (level=0xc049befa "<6>", dev=0xd93f8468,
vaf=0xd847be74) at drivers/base/core.c:1846
#11 0xc020b60c in _dev_info (dev=
USB device number %d using %s\n") at drivers/base/core.c:1895
#12 0xc02581f4 in hub_port_init (hub=0xd93fae00, udev=0xd93f8400, port1=2,
retry_counter=0) at drivers/usb/core/hub.c:2935
#13 0xc025abf0 in hub_port_connect_change (__unused=
drivers/usb/core/hub.c:3329
#14 hub_events (__unused=
#15 hub_thread (__unused=
#16 0xc0042b94 in kthread (_create=0xd805befc) at kernel/kthread.c:121
#17 0xc000e820 in kernel_thread_helper ()
Backtrace stopped: frame did not save the PC
(gdb) l
939
**/
940
static void xuartps_console_wait_tx(struct uart_port *port)
941
{
942
//
unsigned int timeout = 10000;
943
944
while ((xuartps_readl(XUARTPS_SR_OFFSET) & XUARTPS_SR_TXEMPTY)
945
!= XUARTPS_SR_TXEMPTY)
946
//
!= XUARTPS_SR_TXEMPTY && --timeout)
947
barrier();
948
}