• State Suggested Answer
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 20 subscribers
  • Views 662 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

In the A15 fast model, when an unaligned (instruction) happens, will the system timer stalls too?

YP.Lu

I have a tight loop listed as follow. thumb-2. Using the fast model.

PC=0x700abdfe DISASS="MRRC     p15,#0,r0,r1,c14"

PC=0x700abe02 DISASS="SUBS     r0,r0,r2"

PC=0x700abe04 DISASS="SBC      r1,r1,r3"

PC=0x700abe08 DISASS="SUBS     r0,r0,r4"

PC=0x700abe0a DISASS="SBCS     r1,r1,r5"

PC=0x700abe0c DISASS="BCC      {pc}-0xe ; 0x700abdfe"

The target address,0x700abdfe, is not 4 byte aligned, the performance hit is huge.

The real issue is that when cpu stalls, the timer slows down too, which doesn't make sense.

"MRRC     p15,#0,r0,r1,c14" reads the timer register  which shouldn't matter if this loop is going slowly.

Are there any known issues regarding the timer s in the fast model?