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;;                                                                          ;;
;; This file is part of 'M', a MIPS system emulator.                        ;;
;;                                                                          ;;
;; (C) 2019 Stanislav Datskovskiy ( www.loper-os.org )                      ;;
;; http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     ;;
;;                                                                          ;;
;; You do not have, nor can you ever acquire the right to use, copy or      ;;
;; distribute this software ; Should you use this software for any purpose, ;;
;; or copy and distribute it to anyone or in any manner, you are breaking   ;;
;; the laws of whatever soi-disant jurisdiction, and you promise to         ;;
;; continue doing so for the indefinite future. In any case, please         ;;
;; always : read and understand any software ; verify any PGP signatures    ;;
;; that you use - for any purpose.                                          ;;
;;                                                                          ;;
;; See also http://trilema.com/2015/a-new-software-licensing-paradigm .     ;;
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;; TODO: Make the interval programmable. Right now hogs MMIO entirely in vain.

;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Interval Clock Device ;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;

;-----------------------------------------------------------------------------
; Interval Clock MMIO:
DECLARE_BUS_DEVICE CLOCK, 0x420, 0x42F
;-----------------------------------------------------------------------------

;-----------------------------------------------------------------------------
; Interval Clock IRQ:
;-----------------------------------------------------------------------------
%define CLOCK_IRQ   3 ; UART0 Receiver Slave IRQ
;-----------------------------------------------------------------------------

;-----------------------------------------------------------------------------
; Interval Clock State
;-----------------------------------------------------------------------------
section .bss
        CLOCK_Die   resd    1             ; Shutdown Trigger
;-----------------------------------------------------------------------------

section .text

;-----------------------------------------------------------------------------
_PD_Read_Word_CLOCK:                      ; Word reads from CLOCK always 0
        xor     eax, eax
        ret                               ; Fin.
;-----------------------------------------------------------------------------
_PD_Write_Word_CLOCK:                     ; Word writes to CLOCK do nothing!
        ret
;-----------------------------------------------------------------------------
_PD_Read_Byte_CLOCK:
        xor     eax, eax                  ; Read Byte from CLOCK: always 0
        ret
;-----------------------------------------------------------------------------
_PD_Write_Byte_CLOCK:
        ret                               ; Fin.
;-----------------------------------------------------------------------------
_Device_Init_CLOCK:
        mov     rdi, _Clock_Slave         ; Clock Slave
        call    _Create_Thread            ; Start the Clock Slave Thread
        ret
;-----------------------------------------------------------------------------
_Device_Shutdown_CLOCK:                   ; Shutdown
        mov     dword [CLOCK_Die], 0x01   ; Ask (unblocked) slave to die
        ret
;-----------------------------------------------------------------------------

;-----------------------------------------------------------------------------
_Clock_Slave:
        mov     rax, _clock_interval_ts   ; Set the 'nanosleep' interval
        call    _Nano_Sleep               ; Sleep for the given interval (nS)
        SetSlaveIRQ CLOCK_IRQ             ; Invoke timer slave interrupt
        cmp     dword [CLOCK_Die], 0x01   ; time to die?
        jne     _Clock_Slave              ; if not, keep going.
        jmp     _exit_thread              ; terminate thread
;-----------------------------------------------------------------------------

section .rodata

;-----------------------------------------------------------------------------
; TS for Clock Slave interval:
_clock_interval_ts:
        dq 0                              ; seconds
        dq TIMER_SLAVE_PERIOD             ; nanoseconds
;-----------------------------------------------------------------------------