8.2.22. xilinx-zynq#

This BSP supports the Xilinx Zynq range of devices. This family of devices contain the same ARM hard IP and the different parts have different sizes of programable logic.

The BSP defaults may need to be adjusted using configure BSP options to match the size of memory your board may have.

8.2.22.1. Bootloader#

The bootloader initialises the Zynq device. The Xilinx tool provide an interface to configure the hardware. This is includes the buses, clocks, memory and UART board rate. The output of this is called ps7_init and it a C file. The Xilinx SDK builds a first stage boot loader (FSBL) using this file.

The U-Boot boot loader has it’s own FSBL called MLO to initialise the hardware.

8.2.22.2. Clocks#

An application can provide a function called:

uint32_t a9mpcore_clock_periphclk(void);

to return the peripheral clock. Normally this is half the CPU clock. This function is declared weak so you can override the default behaviour by providing it in your application.

8.2.22.3. Console#

The console driver for the UARTs will always be initialized to a baud rate of 115200 with 8 bit characters, 1 stop bit and no parity bits during start up. Previous configurations programmed into the hardware by the Xilinx tools or a bootloader will be overwritten.

The settings for the console driver can be changed by the user application through the termios API afterwards.

8.2.22.4. Network#

The Cadence network interface driver of LibBSD works on the Xilinx Zynq platform. The hardware checksum support works on real hardware but does not seem to be supported on Qemu therefore the default state is to disable IFCAP_TXCSUM and IFCAP_RXCSUM and this can be enabled from the shell with:

ifconfig cgem0 rxcsum txcsum

or with an ioctl() call to the network interface driver with SIOCSIFCAP and the mask IFCAP_TXCSUM and IFCAP_RXCSUM set.

8.2.22.5. Debugging with xilinx_zynq_a9_qemu#

To debug an application add the QEMU options -s. If you need to debug an initialisation issue also add -S. For example to debug a networking application you could use:

qemu-system-arm -M xilinx-zynq-a9 -m 256M -no-reboot -serial \
    null -serial mon:stdio -nographic \
    -net nic,model=cadence_gem -net vde,id=vde0,sock=/tmp/vde1 \
    -kernel myapp.exe \
    -s -S

Start GDB with the same executable QEMU is running and connect to the QEMU GDB server:

(gdb) target remote :1234

If your application is crashing set a breakpoint on the fatal error handler:

(gdb) b bsp_fatal_extension

Enter continue to run the application. Running QEMU loads the executable and initialises the CPU. If the -S option is provided the CPU is held in reset. Without the option the CPU runs starting RTEMS. Either way you are connecting to set up target and all you need to do is continue:

(gdb) c

If you have a crash and the breakpoint on bsp_fatal_extension is hit, load the following a GDB script:

 define arm-crash
  set $code = $arg0
  set $r0 = ((const rtems_exception_frame *) $code)->register_r0
  set $r1 = ((const rtems_exception_frame *) $code)->register_r1
  set $r2 = ((const rtems_exception_frame *) $code)->register_r2
  set $r3 = ((const rtems_exception_frame *) $code)->register_r3
  set $r4 = ((const rtems_exception_frame *) $code)->register_r4
  set $r5 = ((const rtems_exception_frame *) $code)->register_r5
  set $r6 = ((const rtems_exception_frame *) $code)->register_r6
  set $r7 = ((const rtems_exception_frame *) $code)->register_r7
  set $r8 = ((const rtems_exception_frame *) $code)->register_r8
  set $r9 = ((const rtems_exception_frame *) $code)->register_r9
  set $r10 = ((const rtems_exception_frame *) $code)->register_r10
  set $r11 = ((const rtems_exception_frame *) $code)->register_r11
  set $r12 = ((const rtems_exception_frame *) $code)->register_r12
  set $sp = ((const rtems_exception_frame *) $code)->register_sp
  set $lr = ((const rtems_exception_frame *) $code)->register_lr
  set $pc = ((const rtems_exception_frame *) $code)->register_pc
  set $cpsr = ((const rtems_exception_frame *) $code)->register_cpsr
end

Enter the command:

(gdb) arm-crash code

Enter bt to see the stack back trace.

The script moves the context back to the crash location. You should be able to view variables and inspect the stack.

The fatal error handler runs inside an exception context that is not the one than generated the exception.

xilinx-zynq

Contents