/* * This file is part of the COMROGUE Operating System for Raspberry Pi * * Copyright (c) 2013, Eric J. Bowersox / Erbosoft Enterprises * All rights reserved. * * This program is free for commercial and non-commercial use as long as the following conditions are * adhered to. * * Copyright in this file remains Eric J. Bowersox and/or Erbosoft, and as such any copyright notices * in the code are not to be removed. * * Redistribution and use in source and binary forms, with or without modification, are permitted * provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, this list of conditions and * the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and * the following disclaimer in the documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * * "Raspberry Pi" is a trademark of the Raspberry Pi Foundation. */ #define __COMROGUE_PRESTART__ #include #include #include #include /*------------------------------------------------------------------------------------------ * The prestart code that gets control when the kernel is first loaded; its objective is to * set up the MMU and hand over control to the actual start code. *------------------------------------------------------------------------------------------ */ .section ".first.prestart.text" .globl COMROGUEPrestart /* On entry: r0 = 0, r1 = machine type, r2 = atags address */ COMROGUEPrestart: /* Initialize a temporary stack area. */ mov ip, # PHYSADDR_LOAD sub sp, ip, #4 /* Go collect the startup info. */ bl KiCollectStartupInfo mov r11, r0 /* r11 = address of startup info structure */ /* at this point r0-r2 are free for other code to use */ /* Early trace initialize; we reinitialize it later. */ bl ETrInit ldr r0, =.initMessage bl ETrWriteString8 /* Copy the early vector table into place, including the vector words that live after the table itself. */ ldr r0, =.earlyVectorTable ldr r1, =.earlyVectorTableEnd mov r2, #0 b .vec1 .vec0: ldm r0!, {r3-r6} /* copy 16 bytes at a time */ stm r2!, {r3-r6} .vec1: cmp r0, r1 bne .vec0 /* Initialize early memory management (the TTB1). */ mov r0, r11 bl EMmInit mov r10, r0 /* r10 = address of TTB */ /* Set up and start the MMU. */ mov ip, #0 mcr p15, 0, ip, c7, c7, 0 /* clear caches */ mcr p15, 0, ip, c8, c7, 0 /* clear TLB */ mov ip, #1 mcr p15, 0, ip, c2, c0, 2 /* set TTBCR */ mvn ip, #0 mcr p15, 0, ip, c3, c0, 0 /* configure domain 0 = client, all others = invalid */ mcr p15, 0, r10, c2, c0, 0 /* set TTB0 */ mcr p15, 0, r10, c2, c0, 1 /* set TTB1 */ mrc p15, 0, ip, c1, c0, 0 /* get control register 1 */ orr ip, ip, # SCTLR_M /* MMU = on */ orr ip, ip, # SCTLR_XP /* subpage AP bits disabled in 2nd-level page tables */ instr_barrier mcr p15, 0, ip, c1, c0, 0 /* store control register 1 */ mrc p15, 0, ip, c0, c0, 0 /* read ID register */ instr_barrier #if 0 ldr r0, =.msg1 bl ETrWriteString8 #endif /* now go to the start area in kernel space */ mov r0, r11 ldr ip, =COMROGUEStart mov pc, ip #if 0 .balign 4 .msg1: .asciz "got here 1\n" .balign 4 #endif /*------------------------------------------------------------- * Early exception-handler code, mainly for debugging purposes *------------------------------------------------------------- */ .earlyReset: ldr r0, =.resetMessage b .earlyFUBAR .earlyUndef: ldr r0, =.undefMessage b .earlyFUBAR .earlySVC: ldr r0, =.svcMessage b .earlyFUBAR .earlyPrefetch: ldr r0, =.prefetchMessage b .earlyFUBAR .earlyData: ldr r0, =.dataMessage b .earlyFUBAR .earlyHyp: ldr r0, =.hypMessage b .earlyFUBAR .earlyIRQ: ldr r0, =.irqMessage b .earlyFUBAR .earlyFIQ: ldr r0, =.fiqMessage .earlyFUBAR: bl ETrWriteString8 .hang: wfe b .hang .earlyVectorTable: ldr pc, .resetVector ldr pc, .undefVector ldr pc, .svcVector ldr pc, .prefetchVector ldr pc, .dataVector ldr pc, .hypVector ldr pc, .irqVector ldr pc, .fiqVector .resetVector: .word .earlyReset .undefVector: .word .earlyUndef .svcVector: .word .earlySVC .prefetchVector: .word .earlyPrefetch .dataVector: .word .earlyData .hypVector: .word .earlyHyp .irqVector: .word .earlyIRQ .fiqVector: .word .earlyFIQ .earlyVectorTableEnd: .balign 4 .initMessage: .asciz "COMROGUEPrestart\n" .balign 4 .resetMessage: .asciz "+++ RESET!!!\n" .balign 4 .undefMessage: .asciz "+++ UNDEF!!!\n" .balign 4 .svcMessage: .asciz "+++ SVC!!!\n" .balign 4 .prefetchMessage: .asciz "+++ PREFETCH!!!\n" .balign 4 .dataMessage: .asciz "+++ DATA!!!\n" .balign 4 .hypMessage: .asciz "+++ HYP!!!\n" .balign 4 .irqMessage: .asciz "+++ IRQ!!!\n" .balign 4 .fiqMessage: .asciz "+++ FIQ!!!\n" /*-------------------------------------------------------------------------------------- * Low-level IO functions that are placed here to make them callable from prestart code *-------------------------------------------------------------------------------------- */ .section ".prestart.text" /* * Writes a 32-bit word of data to a memory-mapped IO port. * * Parameters: * - paPort = Physical address of the IO port to write to. * - uiData = Data to be written. * * Returns: * Nothing. * * Side effects: * Writing to any given IO port may have arbitrary side effects. */ .globl llIOWritePA llIOWritePA: str r1,[r0] bx lr /* * Reads a 32-bit word of data from a memory-mapped IO port. * * Parameters: * - paPort = Physical address of the IO port we read from. * * Returns: * The word of data read from the IO port. * * Side effects: * Reading from any given IO port may have arbitrary side effects. */ .globl llIOReadPA llIOReadPA: ldr r0,[r0] bx lr /* * Delays for a certain number of cycles, to allow an IO operation to work. * * Parameters: * - uiTicks = The number of "ticks" to delay. * * Returns: * Nothing. */ .globl llIODelayPA llIODelayPA: push {lr} .delaytop: nop nop bl .delayreturn nop nop subs r0, r0, #1 bne .delaytop pop {lr} .delayreturn: bx lr