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MIPS: CPS: Early debug using an ns16550-compatible UART

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Provide support for outputting early debug information, in the form of
various register values should an exception occur, during the early
bringup of secondary cores. This code requires an ns16550-compatible
UART accessible from the secondary core, and is written in assembly due
to the environment in which such early exceptions occur where way may
not have a stack, be coherent or even have initialised caches.

[ralf@linux-mips.org: Fix merge conflict.]

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11202/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton
2015-09-22 11:12:11 -07:00
committed by Ralf Baechle
parent 195cee92af
commit 609cf6f229
5 changed files with 252 additions and 0 deletions
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20
arch/mips/kernel/cps-vec.S
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@@ -31,6 +31,20 @@
# define STATUS_BITDEPS 0
#endif
#ifdef CONFIG_MIPS_CPS_NS16550
#define DUMP_EXCEP(name) \
PTR_LA a0, 8f; \
jal mips_cps_bev_dump; \
nop; \
TEXT(name)
#else /* !CONFIG_MIPS_CPS_NS16550 */
#define DUMP_EXCEP(name)
#endif /* !CONFIG_MIPS_CPS_NS16550 */
/*
* Set dest to non-zero if the core supports the MT ASE, else zero. If
* MT is not supported then branch to nomt.
@@ -194,36 +208,42 @@ dcache_done:
.org 0x200
LEAF(excep_tlbfill)
DUMP_EXCEP("TLB Fill")
b .
nop
END(excep_tlbfill)
.org 0x280
LEAF(excep_xtlbfill)
DUMP_EXCEP("XTLB Fill")
b .
nop
END(excep_xtlbfill)
.org 0x300
LEAF(excep_cache)
DUMP_EXCEP("Cache")
b .
nop
END(excep_cache)
.org 0x380
LEAF(excep_genex)
DUMP_EXCEP("General")
b .
nop
END(excep_genex)
.org 0x400
LEAF(excep_intex)
DUMP_EXCEP("Interrupt")
b .
nop
END(excep_intex)
.org 0x480
LEAF(excep_ejtag)
DUMP_EXCEP("EJTAG")
PTR_LA k0, ejtag_debug_handler
jr k0
nop