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Why don't I see PMUFW XPfw_Printfs: A Debug Story
- Zach Pfeffer
- Jun 5, 2018
- 2 min read
This post list my debug of why I don't see XPfw_Print() output from PMUFW included in PetaLinux Tools 2017.4.
TL;DR
There's no UART output because the PS UART is not on when I load PMUFW.
Related
Symptom
I don't see this print from XPfw_Main():
File:
Hypothesis 1
I don't see XPfw_Printf because there's a missing DEBUG define
Info
Where is XPfw_Printf?
Grep:
Output:
Relevant Lines in xpfw_debug.h:
Test Hypothesis 1
Are XPFW_DEBUG_DETAILED, XPFW_DEBUG_ERROR and XPFW_PRINT?
Method
Use #error's in the code and recompile. See link for how to recompile PMUFW.
Compile
Compile Output
Who defines XPFW_PRINT?
Its not defined on the command line, no -DXPFW_PRINT
Grep
Output
Defined in xpfw_config.h
Which is included in xpfw_default.h as seen here
Grep
Output
...which was referenced in the debug output.
Hypothesis 1 Conclusion
Hypothesis 1 is not true. There is a define that should allow me to see DEBUG_PRINT_ALWAYS.
Hypothesis 2
I never get to the print.
Method
Use an infinite loop before the print and break in with xsct over JTAG.
Change:
Recompile
Add the path to it to PATH in a local window:
Check it:
Run it, look at xsct output
Find XPfw_Main
In xsct
Run targets
Read the registers
The PC matches the bri line from above. So that shows we can get to this line of code.
Do I get into the print, does the print do anything?
Look for any XPfw_Printf's
Empty! Weird.
If I remove the spin loop, will the XPfw_Printf's still be present?
Yes:
Start stepping into prints
Set a breakpoint on 0xffdc7270
To set the breakpoint:
Enumerate targets
Select the PMU and dump registers
Set the breakpoint
Hmm... can't set a hardware breakpoint, set a software breakpoint instead:
Reset unit via external power suppy
Continue setting breakpoints until the the UART FIFO gets written
See the breakpoint on 0xffdc7270, the call to xil_printf, get hit
Step one instruction
Look at the backtrace
Step one instruction and disassemble
Correlate addresses with instructions
Set a breakpoint on outbyte, continued, dissemble, look at the backtrace
Correlate addresses with instructions
Get the address
Set a breakpoint on the instruction that actually writes to the UART hardware ands continue until you get to that line
Decode swi r6, r5, 48 with the Registers
r6 (rD) is 0x50
r5 (rA) is 0xff000000
IMM is 48 or 0x30
Replacing text: Store 0x50 (Ascii 'P') to 0xff000030
The P comes from "PMU Firm...":
0xff000030 is the TX FIFO of UART 0
Try reading and writing to of ff000030 from xsct
Bingo!
There is no output because the UART is not on at this point! I'm loading the PMUFW first with:
And the other systems are reporting:
So I either need to wait longer to see these prints, print them to UART1 or figure out something else.
References