Xilinx ZynqMP SPL boot: psu_init_gpl.c code corrupts U-Boot memory

[Michal Simek]

Hi,

On 1/20/21 9:25 PM, Robert Hancock wrote:
> I've been trying to get the U-Boot SPL to work on a Xilinx ZCU102
> development board. I have been testing with U-Boot 2021.01, and using
> the generated psu_init_gpl HW initialization code generated by Vivado
> 2020.2, rather than the versions in the U-Boot tree, as we are
> expecting to make changes to the configuration as we move to our own
> board design.
> 
> The issue I was seeing is that the SPL seemingly locking up or crashing
> early in the boot process, just after the SPL banner was printed. I've
> CCed "Major A" as he reported something similar on the mailing list in
> March ('ZynqMP boot: no messages from SPL other than "Debug uart
> enabled"') but I didn't see a resoution posted.
> 
> After groveling around with the Xilinx JTAG debugger for a day or so, I
> figured out that the problem was that the SPL ended up reading from an
> invalid pointer address somewhere during the driver model
> initialization process, and crashing. After using memory watchpoints to
> identify where the bogus value was being written to the pointer storage
> location, the memory write was actually coming from the Vivado 2020.2-
> generated psu_init_gpl code. The offending code is in a function called
> serdes_illcalib_pcie_gen1 and looks like this:
> 
>           if (gen2_calib != 1) 
>           {
>             ill1_val[loop] = ((0x04 + meancount[loop]*8) % 0x100);
>             ill12_val[loop] = ((0x04 + meancount[loop]*8) >= 0x100) ?
> 0x10 : 0x00;
>             Xil_Out32(0xFFFE0000+loop*4,iterresult[loop]);
>             Xil_Out32(0xFFFE0010+loop*4,iterresult[loop+4]);
>             Xil_Out32(0xFFFE0020+loop*4,bistpasscount[loop]);
>             Xil_Out32(0xFFFE0030+loop*4,meancount[loop]);
>           }
>           if (gen2_calib == 1) 
>           {
>             ill1_val[loop] = ((0x104 + meancount[loop]*8) % 0x100);
>             ill12_val[loop] = ((0x104 + meancount[loop]*8) >= 0x200) ?
> 0x02 : 0x01;
>             Xil_Out32(0xFFFE0040+loop*4,iterresult[loop]);
>             Xil_Out32(0xFFFE0050+loop*4,iterresult[loop+4]);
>             Xil_Out32(0xFFFE0060+loop*4,bistpasscount[loop]);
>             Xil_Out32(0xFFFE0070+loop*4,meancount[loop]);
>           }
> 
> Those writes to 0xFFFExxxx are to on-chip memory addresses, not any
> hardware register, so I have no idea what this is trying to achieve.
> Possibly this is some debug code to store some calibration results that
> was left in by mistake? Those addresses may not be used in the Xilinx
> FSBL, but overwriting them in the U-Boot SPL wreaks havoc.
> 
> For now, I've worked around it by hacking the Xil_Out32 implementation
> provided by U-Boot in board/xilinx/zynqmp/xil_io.h to trap and ignore
> writes to memory addresses in the OCRAM range (0xFFFC0000 to
> 0xFFFFFFFF). With that in place, things seem to be working. Probably
> this should be addressed in the Vivado psu_init code generator, but we
> may need some workaround like this to avoid those using the affected
> Xilinx tool versions from hitting this issue?
> 

I can't see any code like this in u-boot code. I can't see context of
this code that's why simply don't know what it does and why.

And also not sure what you want me to do with this. Please suggest.

Thanks,
Michal