/*
* Assembly Language Functions for MIPS MT SMTC support
*/
/*
* This file should be built into the kernel only if CONFIG_MIPS_MT_SMTC is set. */
#include <asm/regdef.h>
#include <asm/asmmacro.h>
#include <asm/stackframe.h>
#include <asm/irqflags.h>
/*
* "Software Interrupt" linkage.
*
* This is invoked when an "Interrupt" is sent from one TC to another,
* where the TC to be interrupted is halted, has it's Restart address
* and Status values saved by the "remote control" thread, then modified
* to cause execution to begin here, in kenel mode. This code then
* disguises the TC state as that of an exception and transfers
* control to the general exception or vectored interrupt handler.
*/
.set noreorder
/*
The __smtc_ipi_vector would use k0 and k1 as temporaries and
1) Set EXL (this is per-VPE, so this can't be done by proxy!)
2) Restore the K/CU and IXMT bits to the pre "exception" state
(EXL means no interrupts and access to the kernel map).
3) Set EPC to be the saved value of TCRestart.
4) Jump to the exception handler entry point passed by the sender.
CAN WE PROVE THAT WE WON'T DO THIS IF INTS DISABLED??
*/
/*
* Reviled and slandered vision: Set EXL and restore K/CU/IXMT
* state of pre-halt thread, then save everything and call
* thought some function pointer to imaginary_exception, which
* will parse a register value or memory message queue to
* deliver things like interprocessor interrupts. On return
* from that function, jump to the global ret_from_irq code
* to invoke the scheduler and return as appropriate.
*/
#define PT_PADSLOT4 (PT_R0-8)
#define PT_PADSLOT5 (PT_R0-4)
.text
.align 5
FEXPORT(__smtc_ipi_vector)
.set noat
/* Disable thread scheduling to make Status update atomic */
DMT 27 # dmt k1
_ehb
/* Set EXL */
mfc0 k0,CP0_STATUS
ori k0,k0,ST0_EXL
mtc0 k0,CP0_STATUS
_ehb
/* Thread scheduling now inhibited by EXL. Restore TE state. */
andi k1,k1,VPECONTROL_TE
beqz k1,1f
emt
1:
/*
* The IPI sender has put some information on the anticipated
* kernel stack frame. If we were in user mode, this will be
* built above the saved kernel SP. If we were already in the
* kernel, it will be built above the current CPU SP.
*
* Were we in kernel mode, as indicated by CU0?
*/
sll k1,k0,3
.set noreorder
bltz k1,2f
move k1,sp
.set reorder
/*
* If previously in user mode, set CU0 and use kernel stack.
*/
li k1,ST0_CU0
or k1,k1,k0
mtc0 k1,CP0_STATUS
_ehb
get_saved_sp
/* Interrupting TC will have pre-set values in slots in the new frame */
2: subu k1,k1,PT_SIZE
/* Load TCStatus Value */
lw k0,PT_TCSTATUS(k1)
/* Write it to TCStatus to restore CU/KSU/IXMT state */
mtc0 k0,$2,1
_ehb
lw k0,PT_EPC(k1)
mtc0 k0,CP0_EPC
/* Save all will redundantly recompute the SP, but use it for now */
SAVE_ALL
CLI
TRACE_IRQS_OFF
move a0,sp
/* Function to be invoked passed stack pad slot 5 */
lw t0,PT_PADSLOT5(sp)
/* Argument from sender passed in stack pad slot 4 */
lw a1,PT_PADSLOT4(sp)
jalr t0
nop
j ret_from_irq
nop
/*
* Called from idle loop to provoke processing of queued IPIs
* First IPI message in queue passed as argument.
*/
LEAF(self_ipi)
/* Before anything else, block interrupts */
mfc0 t0,CP0_TCSTATUS
ori t1,t0,TCSTATUS_IXMT
mtc0 t1,CP0_TCSTATUS
_ehb
/* We know we're in kernel mode, so prepare stack frame */
subu t1,sp,PT_SIZE
sw ra,PT_EPC(t1)
sw a0,PT_PADSLOT4(t1)
la t2,ipi_decode
sw t2,PT_PADSLOT5(t1)
/* Save pre-disable value of TCStatus */
sw t0,PT_TCSTATUS(t1)
j __smtc_ipi_vector
nop
END(self_ipi)
