Questions about writing custom boot loader, Zynq, Zybo

[Thomas Skibo]

> I have the following problems while the kernel is booting:
> 
> 1. RS232 port switches to double speed when the kernel starts printing
> (230400 baud instead of 115200 baud).

This may be due to a clock not getting initialized correctly.  See below.

> 
> 2. The ethernet driver cannot find the MAC address

The ethernet address is set by u-boot.  Without an ethernet address, the driver (cgem) is supposed to pick a random one.

> 
> 3. Is there anything special about how the Zynq is configured in
> ps7_init.c?

Absolutely.  ps7_init.c sets up all the clocks and DDR parameters and is very board specific.  This might be why you’re having problems with the RS232 port.  The clock settings may not match the clock values in the dtb.

> 
> 4. Is the exact ps7_init.c that Thomas Skibo used for his Zybo binaries
> available anywhere?

I build the u-boot binaries from sources at https://github.com/Xilinx/u-boot-xlnx, specifically release v2016.1.  The ps7_init.c and ps7_init.h used are in directory board/xilinx/zynq/zybo_hw_platform.  There are ps7_init.[ch] for other boards there too.


—
Thomas Skibo
thomasskibo at yahoo.com