MIPS: MT: Remove SMTC support

Nobody is maintaining SMTC anymore and there also seems to be no userbase.
Which is a pity - the SMTC technology primarily developed by Kevin D.
Kissell <kevink@paralogos.com> is an ingenious demonstration for the MT
ASE's power and elegance.

Based on Markos Chandras <Markos.Chandras@imgtec.com> patch
https://patchwork.linux-mips.org/patch/6719/ which while very similar did
no longer apply cleanly when I tried to merge it plus some additional
post-SMTC cleanup - SMTC was a feature as tricky to remove as it was to
merge once upon a time.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 0 insertions, 133 deletions

diff --git a/arch/mips/kernel/smtc-asm.S b/arch/mips/kernel/smtc-asm.S
deleted file mode 100644
index 2866863a39df..000000000000
--- a/arch/mips/kernel/smtc-asm.S
+++ /dev/null
@@ -1,133 +0,0 @@
-/*
- * 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)
-#ifdef CONFIG_CPU_MICROMIPS
-	nop
-#endif
-	.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
-	/* Function to be invoked passed stack pad slot 5 */
-	lw	t0,PT_PADSLOT5(sp)
-	/* Argument from sender passed in stack pad slot 4 */
-	lw	a0,PT_PADSLOT4(sp)
-	LONG_L	s0, TI_REGS($28)
-	LONG_S	sp, TI_REGS($28)
-	PTR_LA	ra, ret_from_irq
-	jr	t0
-
-/*
- * 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)