From: Matthew Fortune <Matthew.Fortune@imgtec.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH 2/9] MIPS: fix ROM exception vectors
Date: Mon, 26 Sep 2016 07:58:05 +0000 [thread overview]
Message-ID: <6D39441BF12EF246A7ABCE6654B023537E511886@HHMAIL01.hh.imgtec.org> (raw)
In-Reply-To: <20160925180532.19800-3-daniel.schwierzeck@gmail.com>
Daniel Schwierzeck <daniel.schwierzeck@gmail.com> writes:
> When booting from ROM, early exceptions can't be handled
> properly. Instead of busy-looping give the developer the
> possibilty to examine the situation. Thus issue a SDBBP
> instruction to transfer control to hardware debugger if one
> is attached.
You could make the SDBBP into a UHI operation that can be read by
a debugger as an unhandled exception rather than an unexpected
breakpoint (assuming said debugger knows about UHI). The fragment
I use in lightweight boot code is:
move k0, t9 # Preserve t9
move k1, a0 # Preserve a0
li $25, 15 # UHI exception operation
li $4, 0 # Use hard register context
sdbbp 1 # Invoke UHI operation
You lose k0/k1 in this which may be undesirable but it might
be a reasonable trade off. This shouldn't go in the debug vector
of course!
Matthew
next prev parent reply other threads:[~2016-09-26 7:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-25 18:05 [U-Boot] [PATCH 0/9] MIPS: improve start.S and add exception support Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 1/9] MIPS: make inclusion of ROM exception vectors configurable Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 2/9] MIPS: fix ROM exception vectors Daniel Schwierzeck
2016-09-26 7:58 ` Matthew Fortune [this message]
2016-09-26 17:45 ` Daniel Schwierzeck
2016-09-26 19:03 ` Matthew Fortune
2016-09-25 18:05 ` [U-Boot] [PATCH 3/9] MIPS: fix iand optimize setup of CP0 registers Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 4/9] MIPS: factor out code for initial stack and global data Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 5/9] MIPS: add possibility to setup initial stack and global data in SRAM Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 6/9] MIPS: add asm-offsets for struct pt_regs Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 7/9] MIPS: reserve space for exception vectors Daniel Schwierzeck
2016-09-25 18:05 ` [U-Boot] [PATCH 8/9] MIPS: add handling for generic and EJTAG exceptions Daniel Schwierzeck
2016-09-26 10:29 ` Paul Burton
2016-09-26 17:41 ` Daniel Schwierzeck
2016-09-26 18:15 ` Paul Burton
2016-09-25 18:05 ` [U-Boot] [PATCH 9/9] common/board_f: enable initr_trap for MIPS Daniel Schwierzeck
2016-09-27 0:34 ` Simon Glass
2016-09-26 7:52 ` [U-Boot] [PATCH 0/9] MIPS: improve start.S and add exception support Matthew Fortune
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