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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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26
arch/mips/Kconfig.debug
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@ -159,4 +159,30 @@ config SCACHE_DEBUGFS
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

3
arch/mips/include/asm/mipsregs.h
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@ -52,6 +52,7 @@
#define CP0_INFO $7
#define CP0_HWRENA $7, 0
#define CP0_BADVADDR $8
#define CP0_BADINSTR $8, 1
#define CP0_COUNT $9
#define CP0_ENTRYHI $10
#define CP0_COMPARE $11
@ -59,6 +60,8 @@
#define CP0_CAUSE $13
#define CP0_EPC $14
#define CP0_PRID $15
#define CP0_EBASE $15, 1
#define CP0_CMGCRBASE $15, 3
#define CP0_CONFIG $16
#define CP0_CONFIG3 $16, 3
#define CP0_CONFIG5 $16, 5

1
arch/mips/kernel/Makefile
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@ -51,6 +51,7 @@ obj-$(CONFIG_MIPS_MT_FPAFF) += mips-mt-fpaff.o
obj-$(CONFIG_MIPS_MT_SMP) += smp-mt.o
obj-$(CONFIG_MIPS_CMP) += smp-cmp.o
obj-$(CONFIG_MIPS_CPS) += smp-cps.o cps-vec.o
obj-$(CONFIG_MIPS_CPS_NS16550) += cps-vec-ns16550.o
obj-$(CONFIG_MIPS_GIC_IPI) += smp-gic.o
obj-$(CONFIG_MIPS_SPRAM) += spram.o

202
arch/mips/kernel/cps-vec-ns16550.S Normal file
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@ -0,0 +1,202 @@
/*
* Copyright (C) 2015 Imagination Technologies
* Author: Paul Burton <paul.burton@imgtec.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*/
#include <asm/addrspace.h>
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/mipsregs.h>
#include <asm/regdef.h>
#include <linux/serial_reg.h>
#define UART_TX_OFS (UART_TX << CONFIG_MIPS_CPS_NS16550_SHIFT)
#define UART_LSR_OFS (UART_LSR << CONFIG_MIPS_CPS_NS16550_SHIFT)
/**
* _mips_cps_putc() - write a character to the UART
* @a0: ASCII character to write
* @t9: UART base address
*/
LEAF(_mips_cps_putc)
1: lw t0, UART_LSR_OFS(t9)
andi t0, t0, UART_LSR_TEMT
beqz t0, 1b
sb a0, UART_TX_OFS(t9)
jr ra
END(_mips_cps_putc)
/**
* _mips_cps_puts() - write a string to the UART
* @a0: pointer to NULL-terminated ASCII string
* @t9: UART base address
*
* Write a null-terminated ASCII string to the UART.
*/
NESTED(_mips_cps_puts, 0, ra)
move s7, ra
move s6, a0
1: lb a0, 0(s6)
beqz a0, 2f
jal _mips_cps_putc
PTR_ADDIU s6, s6, 1
b 1b
2: jr s7
END(_mips_cps_puts)
/**
* _mips_cps_putx4 - write a 4b hex value to the UART
* @a0: the 4b value to write to the UART
* @t9: UART base address
*
* Write a single hexadecimal character to the UART.
*/
NESTED(_mips_cps_putx4, 0, ra)
andi a0, a0, 0xf
li t0, '0'
blt a0, 10, 1f
li t0, 'a'
addiu a0, a0, -10
1: addu a0, a0, t0
b _mips_cps_putc
END(_mips_cps_putx4)
/**
* _mips_cps_putx8 - write an 8b hex value to the UART
* @a0: the 8b value to write to the UART
* @t9: UART base address
*
* Write an 8 bit value (ie. 2 hexadecimal characters) to the UART.
*/
NESTED(_mips_cps_putx8, 0, ra)
move s3, ra
move s2, a0
srl a0, a0, 4
jal _mips_cps_putx4
move a0, s2
move ra, s3
b _mips_cps_putx4
END(_mips_cps_putx8)
/**
* _mips_cps_putx16 - write a 16b hex value to the UART
* @a0: the 16b value to write to the UART
* @t9: UART base address
*
* Write a 16 bit value (ie. 4 hexadecimal characters) to the UART.
*/
NESTED(_mips_cps_putx16, 0, ra)
move s5, ra
move s4, a0
srl a0, a0, 8
jal _mips_cps_putx8
move a0, s4
move ra, s5
b _mips_cps_putx8
END(_mips_cps_putx16)
/**
* _mips_cps_putx32 - write a 32b hex value to the UART
* @a0: the 32b value to write to the UART
* @t9: UART base address
*
* Write a 32 bit value (ie. 8 hexadecimal characters) to the UART.
*/
NESTED(_mips_cps_putx32, 0, ra)
move s7, ra
move s6, a0
srl a0, a0, 16
jal _mips_cps_putx16
move a0, s6
move ra, s7
b _mips_cps_putx16
END(_mips_cps_putx32)
#ifdef CONFIG_64BIT
/**
* _mips_cps_putx64 - write a 64b hex value to the UART
* @a0: the 64b value to write to the UART
* @t9: UART base address
*
* Write a 64 bit value (ie. 16 hexadecimal characters) to the UART.
*/
NESTED(_mips_cps_putx64, 0, ra)
move sp, ra
move s8, a0
dsrl32 a0, a0, 0
jal _mips_cps_putx32
move a0, s8
move ra, sp
b _mips_cps_putx32
END(_mips_cps_putx64)
#define _mips_cps_putxlong _mips_cps_putx64
#else /* !CONFIG_64BIT */
#define _mips_cps_putxlong _mips_cps_putx32
#endif /* !CONFIG_64BIT */
/**
* mips_cps_bev_dump() - dump relevant exception state to UART
* @a0: pointer to NULL-terminated ASCII string naming the exception
*
* Write information that may be useful in debugging an exception to the
* UART configured by CONFIG_MIPS_CPS_NS16550_*. As this BEV exception
* will only be run if something goes horribly wrong very early during
* the bringup of a core and it is very likely to be unsafe to perform
* memory accesses at that point (cache state indeterminate, EVA may not
* be configured, coherence may be disabled) let alone have a stack,
* this is all written in assembly using only registers & unmapped
* uncached access to the UART registers.
*/
LEAF(mips_cps_bev_dump)
move s0, ra
move s1, a0
li t9, CKSEG1ADDR(CONFIG_MIPS_CPS_NS16550_BASE)
PTR_LA a0, str_newline
jal _mips_cps_puts
PTR_LA a0, str_bev
jal _mips_cps_puts
move a0, s1
jal _mips_cps_puts
PTR_LA a0, str_newline
jal _mips_cps_puts
PTR_LA a0, str_newline
jal _mips_cps_puts
#define DUMP_COP0_REG(reg, name, sz, _mfc0) \
PTR_LA a0, 8f; \
jal _mips_cps_puts; \
_mfc0 a0, reg; \
jal _mips_cps_putx##sz; \
PTR_LA a0, str_newline; \
jal _mips_cps_puts; \
TEXT(name)
DUMP_COP0_REG(CP0_CAUSE, "Cause: 0x", 32, mfc0)
DUMP_COP0_REG(CP0_STATUS, "Status: 0x", 32, mfc0)
DUMP_COP0_REG(CP0_EBASE, "EBase: 0x", long, MFC0)
DUMP_COP0_REG(CP0_BADVADDR, "BadVAddr: 0x", long, MFC0)
DUMP_COP0_REG(CP0_BADINSTR, "BadInstr: 0x", 32, mfc0)
PTR_LA a0, str_newline
jal _mips_cps_puts
jr s0
END(mips_cps_bev_dump)
.pushsection .data
str_bev: .asciiz "BEV Exception: "
str_newline: .asciiz "\r\n"
.popsection

20
arch/mips/kernel/cps-vec.S
View File

@ -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