MIPS: CPS: Early debug using an ns16550-compatible UART
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>
diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index b43e288..f0e314c 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -159,4 +159,30 @@
If unsure, say N.
+menuconfig MIPS_CPS_NS16550
+ bool "CPS SMP NS16550 UART output"
+ depends on MIPS_CPS
+ help
+ Output debug information via an ns16550 compatible UART if exceptions
+ occur early in the boot process of a secondary core.
+
+if MIPS_CPS_NS16550
+
+config MIPS_CPS_NS16550_BASE
+ hex "UART Base Address"
+ default 0x1b0003f8 if MIPS_MALTA
+ help
+ The base address of the ns16550 compatible UART on which to output
+ debug information from the early stages of core startup.
+
+config MIPS_CPS_NS16550_SHIFT
+ int "UART Register Shift"
+ default 0 if MIPS_MALTA
+ help
+ The number of bits to shift ns16550 register indices by in order to
+ form their addresses. That is, log base 2 of the span between
+ adjacent ns16550 registers in the system.
+
+endif # MIPS_CPS_NS16550
+
endmenu