Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Peter Belm
> > It seems to me that you may still be missing the point that a "b reset" > is an unconditional jump, not a call, i.e. we will never return to the > next instruction. A call would be a "bal reset", i.e. "branch and link" > which puts the address of the next instruction into the $ra register. > O

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Detlev Zundel
Hi Peter, > Why should it?  I presume the CPU starts at _start, so it will "b > reset", i.e. branch (jump) to "reset" and be happy.  Its only if the CPU > jumps to one the reserved vectors that it will loop.  And well, as they > are reserved, this is a legal thing to do, no?  As th

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Chetan Nanda
On Fri, Aug 21, 2009 at 6:23 PM, Peter Belm wrote: > > > > This is not quite correct. "romReserved" is only used for the, well, > > reserved entries. There are other parameters passed, these two are > > pretty important for example: > > > The thing I don't get is if you expand the RVECENT macro

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Peter Belm
> > Why should it? I presume the CPU starts at _start, so it will "b > reset", i.e. branch (jump) to "reset" and be happy. Its only if the CPU > jumps to one the reserved vectors that it will loop. And well, as they > are reserved, this is a legal thing to do, no? As the purple port > works, I'

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Detlev Zundel
Hi Peter, > This is not quite correct.  "romReserved" is only used for the, well, > reserved entries.  There are other parameters passed, these two are > pretty important for example: > > > The thing I don't get is if you expand the RVECENT macro into the code > wouldn't > you get thi

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Peter Belm
> > This is not quite correct. "romReserved" is only used for the, well, > reserved entries. There are other parameters passed, these two are > pretty important for example: The thing I don't get is if you expand the RVECENT macro into the code wouldn't you get this: _start: b reset; nop

Re: [U-Boot] Mips: start.S Questions

2009-08-21 Thread Detlev Zundel
Hi Peter, > I've figured out most of the boot process by following through the code, but > I have a few questions about start.S: > >1. Calls to RVECENT and XVEVENT: what exactly do these do? RVECENT just >branches to the first parameter f, and does nothing with the second >parameter.

[U-Boot] Mips: start.S Questions

2009-08-21 Thread Peter Belm
I've figured out most of the boot process by following through the code, but I have a few questions about start.S: 1. Calls to RVECENT and XVEVENT: what exactly do these do? RVECENT just branches to the first parameter f, and does nothing with the second parameter. Yet the first argument