[U-Boot] [PATCH 0/9] MIPS: improve start.S and add exception support

[Matthew Fortune]

Daniel Schwierzeck <daniel.schwierzeck at gmail.com> writes:
> will be simply exited. The SDBBP handler currently only
> prints the content of registers c0_depc and c0_debug. This
> could be extended in the future to handle semi-hosting
> according to the MIPS UHI specification.

Thanks for considering UHI in this.  I worked on a prototype
implementation of UHI with Paul that is yet to be submitted
which hooks the syscall exception in U-Boot.  There is a way
to avoid going all the way down to debug mode to process a
UHI operation on-target so we can support cores that don't
have ejtag or simply to stay out of debug mode wherever
possible. The basic principle is that either an application
doesn't install its own exception vector and hence uses
U-boot's or it does install its own but remembers where U-boot's
EBASE was and unwinds a SYSCALL exception and forwards it to
U-boot's general-exception handler. It seems to work pretty
well but there is certainly no harm in hooking the debug
vector too.

Matthew