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// TITLE("Processor Idle Support")
//++
//
// Copyright (c) 1992 Digital Equipment Corporation
// Copyright (c) 1993 Digital Equipment Corporation
//
// Module Name:
//
// idle.s
//
// Abstract:
//
// This module implements the HalProcessorIdle interface
//
// Author:
//
// John Vert (jvert) 11-May-1994
//
// Environment:
//
// Revision History:
//
// Wim Colgate, 11-Nov-1995
//
// Modified stub routine to idle the processor on LX3.
//
//--
#include "halalpha.h"
#include "lx3.h"
SBTTL("Processor Idle")
//++
//
// VOID
// HalProcessorIdle(
// VOID
// )
//
// Routine Description:
//
// This function is called when the current processor is idle with
// interrupts disabled. There is no thread active and there are no
// DPCs to process. Therefore, power can be switched to a standby
// mode until the the next interrupt occurs on the current processor.
//
// N.B. This routine is entered with interrupts disabled. This routine
// must do any power management enabling necessary, enable interrupts,
// then either return or wait for an interrupt.
//
// Arguments:
//
// None.
//
// Return Value:
//
// None.
//
// Note:
//
// On LX3, the sequence of events should are:
//
// Write "idle" to processor
// Flush Dcache
// Enable Interrupts
//
// All of the above MUST be loaded into the Icache of the processor
// once we write "idle" to the processor
//
// Once the processor is idle, we cannot get to the backup cache,
// nor main memory. Once an interrupt occurs, the CPU reattaches via
// hardware magic.
//
//--
LEAF_ENTRY(HalProcessorIdle)
//
// Enable, then disable interrups to force the PALcode
// enable_interrupt routine into the Icache -- by executing it,
// then back to interrupts disabled.
//
ENABLE_INTERRUPTS
#ifdef IDLE_PROCESSOR
//
// set up temps here - instead of in critical Icache area
// temps are a0-a5, t0-t7
//
lda a0, HalpInterruptReceived
bis zero, 1, t3
stl t3, 0(a0)
//
// set up t5 for superpage mode base address
//
ldiq t5, -0x4000 // 0xffff ffff ffff c000
sll t5, 28, t5 // 0xffff fc00 0000 0000
//
// set t7 for interrupt register to poll on
//
ldah t7, 0x1b(zero) // 0x0000 0000 1b00 0000
sll t7, 4, t7 // 0x0000 0001 b000 0000
bis t5, t7, t7 // 0xffff fc01 b000 0000
//
// set t6 for a 32K constant for Dcache flushing
//
ldil t6, 0x8000 // 0x0000 0000 0000 8000
//
// set a1 to be the 'bouncing' bit
//
bis zero, 1, a1
mb
DISABLE_INTERRUPTS
//
// Flush Dcache -- start at superpage address 0 and read 32K worth of
// data
//
flush: ldl t1, 0(t5) // read data
addl t5, 0x20, t5 // increment location by 8 longwords
and t5, t6, t4 // check for 32K limit
bne t4, setspin // loop finished
br zero, flush // branch back
bne a1, touch1 // bounce ahead to touch1
continue:
//
// clear a1 (aka the bouncing bit) so that we actually execite code
// now.
bis zero, zero, a1
//
// Power down the processor to 'idle speed', which is not
// completelty off. Duh.
//
ldil t0, CONFIG_REGISTER_SMALL // 0x0000 0000 0000 1001
sll t0, 20, t0 // 0x0000 0001 0010 0000
bis t0, t5, t0 // 0xffff fc01 0010 0000
ldil t2, CONFIG_SELECT_IDLE // load idle setting
stl t2, 0(t0) // set processor to idle
//
// Past this point, all instructions MUST be in the Icache
//
//
// Enable Interrupts
//
setspin:
ENABLE_INTERRUPTS
//
// spin on the interrupt bit -- cleared by any interrupt routine
//
spin: ldl t0, 0(a0) // load bit
bne t0, spin // spin on bit
touch1: bne a1, continue // go all the way back
#endif
done: ret zero, (ra)
.end HalProcessorIdle
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