/* * ip22-irq.S: Interrupt exception dispatch code for FullHouse and * Guiness. * * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com) */ #include #include #include #include /* A lot of complication here is taken away because: * * 1) We handle one interrupt and return, sitting in a loop and moving across * all the pending IRQ bits in the cause register is _NOT_ the answer, the * common case is one pending IRQ so optimize in that direction. * * 2) We need not check against bits in the status register IRQ mask, that * would make this routine slow as hell. * * 3) Linux only thinks in terms of all IRQs on or all IRQs off, nothing in * between like BSD spl() brain-damage. * * Furthermore, the IRQs on the INDY look basically (barring software IRQs * which we don't use at all) like: * * MIPS IRQ Source * -------- ------ * 0 Software (ignored) * 1 Software (ignored) * 2 Local IRQ level zero * 3 Local IRQ level one * 4 8254 Timer zero * 5 8254 Timer one * 6 Bus Error * 7 R4k timer (what we use) * * We handle the IRQ according to _our_ priority which is: * * Highest ---- R4k Timer * Local IRQ zero * Local IRQ one * Bus Error * 8254 Timer zero * Lowest ---- 8254 Timer one * * then we just return, if multiple IRQs are pending then we will just take * another exception, big deal. */ .text .set noreorder .set noat .align 5 NESTED(indyIRQ, PT_SIZE, sp) SAVE_ALL CLI .set at mfc0 s0, CP0_CAUSE # get irq mask /* First we check for r4k counter/timer IRQ. */ andi a0, s0, CAUSEF_IP7 beq a0, zero, 1f andi a0, s0, CAUSEF_IP2 # delay slot, check local level zero /* Wheee, a timer interrupt. */ jal indy_r4k_timer_interrupt move a0, sp # delay slot j ret_from_irq nop # delay slot 1: beq a0, zero, 1f andi a0, s0, CAUSEF_IP3 # delay slot, check local level one /* Wheee, local level zero interrupt. */ jal indy_local0_irqdispatch move a0, sp # delay slot j ret_from_irq nop # delay slot 1: beq a0, zero, 1f andi a0, s0, CAUSEF_IP6 # delay slot, check bus error /* Wheee, local level one interrupt. */ jal indy_local1_irqdispatch move a0, sp # delay slot j ret_from_irq nop # delay slot 1: beq a0, zero, 1f andi a0, s0, (CAUSEF_IP4 | CAUSEF_IP5) # delay slot /* Wheee, an asynchronous bus error... */ jal indy_buserror_irq move a0, sp # delay slot j ret_from_irq nop # delay slot 1: /* Here by mistake? It is possible, that by the time we take * the exception the IRQ pin goes low, so just leave if this * is the case. */ beq a0, zero, 1f nop # delay slot /* Must be one of the 8254 timers... */ jal indy_8254timer_irq move a0, sp # delay slot 1: j ret_from_irq nop # delay slot END(indyIRQ)
