FreeCalypso > hg > freecalypso-sw
view gsm-fw/sysglue/irqfiq.S @ 428:e61eacecd319
loadtools/README: command line etc description brought over and updated
from README.old
author | Michael Spacefalcon <msokolov@ivan.Harhan.ORG> |
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date | Sat, 21 Jun 2014 17:27:17 +0000 |
parents | afceeeb2cba1 |
children |
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/* * This module contains the assembly shells for IRQ and FIQ, separated * from the architectured vectors only by some simple unconditional * branch instructions. * * Note that TI's way of handling interrupts sacrifices Nucleus' ability * to nest interrupts and minimize the IRQ-disabled window: if my (Falcon's) * understanding is correct, TI's code leaves all further IRQs disabled * for the full execution duration of an IRQ handler. (IRQ handlers are * really LISRs, but TI's GSM fw does not use Nucleus' LISR framework.) */ .section iram.text,"ax",%progbits .code 32 .globl _INT_IRQ _INT_IRQ: STMDB sp!,{r0-r4} @ used to be a1-a4 /* * Thanks to TI for discovering and documenting this apparent ARM7TDMI bug: BUG correction 1st part ------------------- It looks like there is an issue with ARM7 IRQ masking in the CPSR register which leads to crashes in Nucleus+ scheduler. Basically the code below (correct as LOCKOUT = 0xC0) is used in many places by N+ but do not prevent from having an interrupt after the execution of the third line (I mean execution, not fetch). MRS a1,CPSR ; Pickup current CPSR ORR a1,a1,#LOCKOUT ; Build interrupt lockout value MSR CPSR,a1 ; Lockout interrupts * IRQ INTERRUPT ! * Next instructions... SW workaround: When a task is interrupted at this point an interrupted context is stored on its task and will be resumed later on at the next instruction but to make a long story short it leads to some problem as the OS does not expect to be interrupted there. Further testing tends to show that the CPSR *seems* to be loaded with the proper masking value but that the IRQ is still triggered (has been hardwarewise requested during the instruction exectution by the ARM7 core?) */ MRS a1,spsr @ check for the IRQ bug: TST a1,#0x80 @ if the I - flag is set, BNE IRQBUG @ then postpone execution of this IRQ /* Bug correction 1st part end --------------- */ SUB r4,lr,#4 @ Save IRQ's lr (return address) BL TCT_Interrupt_Context_Save @ Call context save routine BL IQ_IRQ_isr @ Call int. service routine /* IRQ interrupt processing is complete. Restore context- Never returns! */ B TCT_Interrupt_Context_Restore /* BUG correction 2nd part ------------------ */ IRQBUG: LDMFD sp!,{r0-r4} @ return from interrupt SUBS pc,r14,#4 /* BUG correction 2nd part end -------------- */ .globl _INT_FIQ _INT_FIQ: STMDB sp!,{r0-r4} @ used to be a1-a4 SUB r4,lr,#4 @ Save FIQ's lr (return address) BL TCT_Interrupt_Context_Save @ Call context save routine BL IQ_FIQ_isr @ Call the FIQ ISR /* FIQ interrupt processing is complete. Restore context- Never returns! */ B TCT_Interrupt_Context_Restore