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[MIPS] SMTC: Interrupt mask backstop hack 

To support multiple TC microthreads acting as "CPUs" within a VPE,
VPE-wide interrupt mask bits must be specially manipulated during
interrupt handling. To support legacy drivers and interrupt controller
management code, SMTC has a "backstop" to track and if necessary restore
the interrupt mask. This has some performance impact on interrupt service
overhead. Disable it only if you know what you are doing.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Kevin D. Kissell 2007-07-12 16:21:08 +01:00 committed by Ralf Baechle
parent bd0765098b
commit 0db34215c7
4 changed files with 18 additions and 1 deletions
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13
arch/mips/Kconfig
View File

@ -1404,6 +1404,19 @@ config MIPS_MT_SMTC_INSTANT_REPLAY
it off), but ensures that IPIs are handled promptly even under
heavy I/O interrupt load.
config MIPS_MT_SMTC_IM_BACKSTOP
bool "Use per-TC register bits as backstop for inhibited IM bits"
depends on MIPS_MT_SMTC
default y
help
To support multiple TC microthreads acting as "CPUs" within
a VPE, VPE-wide interrupt mask bits must be specially manipulated
during interrupt handling. To support legacy drivers and interrupt
controller management code, SMTC has a "backstop" to track and
if necessary restore the interrupt mask. This has some performance
impact on interrupt service overhead. Disable it only if you know
what you are doing.
config MIPS_VPE_LOADER_TOM
bool "Load VPE program into memory hidden from linux"
depends on MIPS_VPE_LOADER

2
arch/mips/kernel/entry.S
View File

@ -84,6 +84,7 @@ FEXPORT(restore_all) # restore full frame
LONG_S sp, TI_REGS($28)
jal deferred_smtc_ipi
LONG_S s0, TI_REGS($28)
#ifdef CONFIG_MIPS_MT_SMTC_IM_BACKSTOP
/* Re-arm any temporarily masked interrupts not explicitly "acked" */
mfc0 v0, CP0_TCSTATUS
ori v1, v0, TCSTATUS_IXMT
@ -110,6 +111,7 @@ FEXPORT(restore_all) # restore full frame
_ehb
xor t0, t0, t3
mtc0 t0, CP0_TCCONTEXT
#endif /* CONFIG_MIPS_MT_SMTC_IM_BACKSTOP */
#endif /* CONFIG_MIPS_MT_SMTC */
.set noat
RESTORE_TEMP

2
arch/mips/kernel/genex.S
View File

@ -243,9 +243,11 @@ NESTED(except_vec_vi_handler, 0, sp)
*/
mfc0 t1, CP0_STATUS
and t0, a0, t1
#ifdef CONFIG_MIPS_MT_SMTC_IM_BACKSTOP
mfc0 t2, CP0_TCCONTEXT
or t0, t0, t2
mtc0 t0, CP0_TCCONTEXT
#endif /* CONFIG_MIPS_MT_SMTC_IM_BACKSTOP */
xor t1, t1, t0
mtc0 t1, CP0_STATUS
_ehb

2
include/asm-mips/irq.h
View File

@ -24,7 +24,7 @@ static inline int irq_canonicalize(int irq)
#define irq_canonicalize(irq) (irq) /* Sane hardware, sane code ... */
#endif
#ifdef CONFIG_MIPS_MT_SMTC
#ifdef CONFIG_MIPS_MT_SMTC_IM_BACKSTOP
/*
* Clear interrupt mask handling "backstop" if irq_hwmask
* entry so indicates. This implies that the ack() or end()