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authorDavid Howells <dhowells@redhat.com>2006-02-14 13:53:20 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-14 16:09:35 -0800
commit28baebae73c3ea8b75c7cae225a7db817ab825a9 (patch)
tree940476b4d03b96480d451b7b5b6f3df3f0ff18dc /arch/frv/kernel/entry.S
parent68f624fc8b9fa50de9cc0ebd612ef7b7b9fa32d0 (diff)
downloadblackbird-op-linux-28baebae73c3ea8b75c7cae225a7db817ab825a9.tar.gz
blackbird-op-linux-28baebae73c3ea8b75c7cae225a7db817ab825a9.zip
[PATCH] FRV: Use virtual interrupt disablement
Make the FRV arch use virtual interrupt disablement because accesses to the processor status register (PSR) are relatively slow and because we will soon have the need to deal with multiple interrupt controls at the same time (separate h/w and inter-core interrupts). The way this is done is to dedicate one of the four integer condition code registers (ICC2) to maintaining a virtual interrupt disablement state whilst inside the kernel. This uses the ICC2.Z flag (Zero) to indicate whether the interrupts are virtually disabled and the ICC2.C flag (Carry) to indicate whether the interrupts are physically disabled. ICC2.Z is set to indicate interrupts are virtually disabled. ICC2.C is set to indicate interrupts are physically enabled. Under normal running conditions Z==0 and C==1. Disabling interrupts with local_irq_disable() doesn't then actually physically disable interrupts - it merely sets ICC2.Z to 1. Should an interrupt then happen, the exception prologue will note ICC2.Z is set and branch out of line using one instruction (an unlikely BEQ). Here it will physically disable interrupts and clear ICC2.C. When it comes time to enable interrupts (local_irq_enable()), this simply clears the ICC2.Z flag and invokes a trap #2 if both Z and C flags are clear (the HI integer condition). This can be done with the TIHI conditional trap instruction. The trap then physically reenables interrupts and sets ICC2.C again. Upon returning the interrupt will be taken as interrupts will then be enabled. Note that whilst processing the trap, the whole exceptions system is disabled, and so an interrupt can't happen till it returns. If no pending interrupt had happened, ICC2.C would still be set, the HI condition would not be fulfilled, and no trap will happen. Saving interrupts (local_irq_save) is simply a matter of pulling the ICC2.Z flag out of the CCR register, shifting it down and masking it off. This gives a result of 0 if interrupts were enabled and 1 if they weren't. Restoring interrupts (local_irq_restore) is then a matter of taking the saved value mentioned previously and XOR'ing it against 1. If it was one, the result will be zero, and if it was zero the result will be non-zero. This result is then used to affect the ICC2.Z flag directly (it is a condition code flag after all). An XOR instruction does not affect the Carry flag, and so that bit of state is unchanged. The two flags can then be sampled to see if they're both zero using the trap (TIHI) as for the unconditional reenablement (local_irq_enable). This patch also: (1) Modifies the debugging stub (break.S) to handle single-stepping crossing into the trap #2 handler and into virtually disabled interrupts. (2) Removes superseded fixup pointers from the second instructions in the trap tables (there's no a separate fixup table for this). (3) Declares the trap #3 vector for use in .org directives in the trap table. (4) Moves irq_enter() and irq_exit() in do_IRQ() to avoid problems with virtual interrupt handling, and removes the duplicate code that has now been folded into irq_exit() (softirq and preemption handling). (5) Tells the compiler in the arch Makefile that ICC2 is now reserved. (6) Documents the in-kernel ABI, including the virtual interrupts. (7) Renames the old irq management functions to different names. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/frv/kernel/entry.S')
-rw-r--r--arch/frv/kernel/entry.S65
1 files changed, 58 insertions, 7 deletions
diff --git a/arch/frv/kernel/entry.S b/arch/frv/kernel/entry.S
index c69d499d28cf..1d21c8d34d8a 100644
--- a/arch/frv/kernel/entry.S
+++ b/arch/frv/kernel/entry.S
@@ -141,7 +141,10 @@ __entry_uspace_external_interrupt_reentry:
movsg gner0,gr4
movsg gner1,gr5
- stdi gr4,@(gr28,#REG_GNER0)
+ stdi.p gr4,@(gr28,#REG_GNER0)
+
+ # interrupts start off fully disabled in the interrupt handler
+ subcc gr0,gr0,gr0,icc2 /* set Z and clear C */
# set up kernel global registers
sethi.p %hi(__kernel_current_task),gr5
@@ -193,9 +196,8 @@ __entry_uspace_external_interrupt_reentry:
.type __entry_kernel_external_interrupt,@function
__entry_kernel_external_interrupt:
LEDS 0x6210
-
- sub sp,gr15,gr31
- LEDS32
+// sub sp,gr15,gr31
+// LEDS32
# set up the stack pointer
or.p sp,gr0,gr30
@@ -231,7 +233,10 @@ __entry_kernel_external_interrupt_reentry:
stdi gr24,@(gr28,#REG_GR(24))
stdi gr26,@(gr28,#REG_GR(26))
sti gr29,@(gr28,#REG_GR(29))
- stdi gr30,@(gr28,#REG_GR(30))
+ stdi.p gr30,@(gr28,#REG_GR(30))
+
+ # note virtual interrupts will be fully enabled upon return
+ subicc gr0,#1,gr0,icc2 /* clear Z, set C */
movsg tbr ,gr20
movsg psr ,gr22
@@ -267,7 +272,10 @@ __entry_kernel_external_interrupt_reentry:
movsg gner0,gr4
movsg gner1,gr5
- stdi gr4,@(gr28,#REG_GNER0)
+ stdi.p gr4,@(gr28,#REG_GNER0)
+
+ # interrupts start off fully disabled in the interrupt handler
+ subcc gr0,gr0,gr0,icc2 /* set Z and clear C */
# set the return address
sethi.p %hi(__entry_return_from_kernel_interrupt),gr4
@@ -291,6 +299,45 @@ __entry_kernel_external_interrupt_reentry:
.size __entry_kernel_external_interrupt,.-__entry_kernel_external_interrupt
+###############################################################################
+#
+# deal with interrupts that were actually virtually disabled
+# - we need to really disable them, flag the fact and return immediately
+# - if you change this, you must alter break.S also
+#
+###############################################################################
+ .balign L1_CACHE_BYTES
+ .globl __entry_kernel_external_interrupt_virtually_disabled
+ .type __entry_kernel_external_interrupt_virtually_disabled,@function
+__entry_kernel_external_interrupt_virtually_disabled:
+ movsg psr,gr30
+ andi gr30,#~PSR_PIL,gr30
+ ori gr30,#PSR_PIL_14,gr30 ; debugging interrupts only
+ movgs gr30,psr
+ subcc gr0,gr0,gr0,icc2 ; leave Z set, clear C
+ rett #0
+
+ .size __entry_kernel_external_interrupt_virtually_disabled,.-__entry_kernel_external_interrupt_virtually_disabled
+
+###############################################################################
+#
+# deal with re-enablement of interrupts that were pending when virtually re-enabled
+# - set ICC2.C, re-enable the real interrupts and return
+# - we can clear ICC2.Z because we shouldn't be here if it's not 0 [due to TIHI]
+# - if you change this, you must alter break.S also
+#
+###############################################################################
+ .balign L1_CACHE_BYTES
+ .globl __entry_kernel_external_interrupt_virtual_reenable
+ .type __entry_kernel_external_interrupt_virtual_reenable,@function
+__entry_kernel_external_interrupt_virtual_reenable:
+ movsg psr,gr30
+ andi gr30,#~PSR_PIL,gr30 ; re-enable interrupts
+ movgs gr30,psr
+ subicc gr0,#1,gr0,icc2 ; clear Z, set C
+ rett #0
+
+ .size __entry_kernel_external_interrupt_virtual_reenable,.-__entry_kernel_external_interrupt_virtual_reenable
###############################################################################
#
@@ -335,6 +382,7 @@ __entry_uspace_softprog_interrupt_reentry:
sethi.p %hi(__entry_return_from_user_exception),gr23
setlo %lo(__entry_return_from_user_exception),gr23
+
bra __entry_common
.size __entry_uspace_softprog_interrupt,.-__entry_uspace_softprog_interrupt
@@ -495,7 +543,10 @@ __entry_common:
movsg gner0,gr4
movsg gner1,gr5
- stdi gr4,@(gr28,#REG_GNER0)
+ stdi.p gr4,@(gr28,#REG_GNER0)
+
+ # set up virtual interrupt disablement
+ subicc gr0,#1,gr0,icc2 /* clear Z flag, set C flag */
# set up kernel global registers
sethi.p %hi(__kernel_current_task),gr5
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