Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*
 * 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
        /* 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)