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linux/arch/microblaze/kernel/head.S
Michal Simek e02db0aa3e microblaze: Handle TLB skip size dynamically 
This patch fix the problem with rootfs on JFFS2 with early printk
console turned on.

The origin version used TLB63 for temporary early printk mapping.
The code expect that kernel is not able to use all 64 TLB entries
till early printk console is remapped by ioremap. After that
temporary mapping on TLB63 is silently lost.
This expectation give the opportunity to have early console pretty
early.

Microblaze systems with JFFS2 rootfs with early printk console turned on
used more than 64 TLB entries before kernel can remap early console.
Based on that kernel does access to bad area because early printk mapping
is rewritten.

This patch introduces tlb_skip variable which dynamically stores number
of skipped TLB entries from the TLB0. skip_tlb=2 means that TLB0 and TLB1
should be skipped.

MICROBLAZE_TLB_SKIP defines how many TLB is skipped at the kernel start.
They can be used for user purpose.

TLB 63 is used for temporary LMB mapping (MICROBLAZE_LMB_TLB_ID).

Also clean TLBLO when kernel starts.

For specific kernel sizes kernel can use just one TLB. Detect this case
and use the second TLB for general purpose.

Change _tlbia function to flush TLB entries from tlb_skip to TLB_SIZE.

Export tlb_skip size through debugfs.

Signed-off-by: Michal Simek <monstr@monstr.eu>
2012-03-23 09:28:19 +01:00

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/*
* Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>
* Copyright (C) 2007-2009 PetaLogix
* Copyright (C) 2006 Atmark Techno, Inc.
*
* MMU code derived from arch/ppc/kernel/head_4xx.S:
* Copyright (c) 1995-1996 Gary Thomas <gdt@linuxppc.org>
* Initial PowerPC version.
* Copyright (c) 1996 Cort Dougan <cort@cs.nmt.edu>
* Rewritten for PReP
* Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au>
* Low-level exception handers, MMU support, and rewrite.
* Copyright (c) 1997 Dan Malek <dmalek@jlc.net>
* PowerPC 8xx modifications.
* Copyright (c) 1998-1999 TiVo, Inc.
* PowerPC 403GCX modifications.
* Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
* PowerPC 403GCX/405GP modifications.
* Copyright 2000 MontaVista Software Inc.
* PPC405 modifications
* PowerPC 403GCX/405GP modifications.
* Author: MontaVista Software, Inc.
* frank_rowand@mvista.com or source@mvista.com
* debbie_chu@mvista.com
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/thread_info.h>
#include <asm/page.h>
#include <linux/of_fdt.h> /* for OF_DT_HEADER */
#ifdef CONFIG_MMU
#include <asm/setup.h> /* COMMAND_LINE_SIZE */
#include <asm/mmu.h>
#include <asm/processor.h>
.section .data
.global empty_zero_page
.align 12
empty_zero_page:
.space PAGE_SIZE
.global swapper_pg_dir
swapper_pg_dir:
.space PAGE_SIZE
#endif /* CONFIG_MMU */
.section .rodata
.align 4
endian_check:
.word 1
__HEAD
ENTRY(_start)
#if CONFIG_KERNEL_BASE_ADDR == 0
brai TOPHYS(real_start)
.org 0x100
real_start:
#endif
mts rmsr, r0
/*
* According to Xilinx, msrclr instruction behaves like 'mfs rX,rpc'
* if the msrclr instruction is not enabled. We use this to detect
* if the opcode is available, by issuing msrclr and then testing the result.
* r8 == 0 - msr instructions are implemented
* r8 != 0 - msr instructions are not implemented
*/
mfs r1, rmsr
msrclr r8, 0 /* clear nothing - just read msr for test */
cmpu r8, r8, r1 /* r1 must contain msr reg content */
/* r7 may point to an FDT, or there may be one linked in.
if it's in r7, we've got to save it away ASAP.
We ensure r7 points to a valid FDT, just in case the bootloader
is broken or non-existent */
beqi r7, no_fdt_arg /* NULL pointer? don't copy */
/* Does r7 point to a valid FDT? Load HEADER magic number */
/* Run time Big/Little endian platform */
/* Save 1 as word and load byte - 0 - BIG, 1 - LITTLE */
lbui r11, r0, TOPHYS(endian_check)
beqid r11, big_endian /* DO NOT break delay stop dependency */
lw r11, r0, r7 /* Big endian load in delay slot */
lwr r11, r0, r7 /* Little endian load */
big_endian:
rsubi r11, r11, OF_DT_HEADER /* Check FDT header */
beqi r11, _prepare_copy_fdt
or r7, r0, r0 /* clear R7 when not valid DTB */
bnei r11, no_fdt_arg /* No - get out of here */
_prepare_copy_fdt:
or r11, r0, r0 /* incremment */
ori r4, r0, TOPHYS(_fdt_start)
ori r3, r0, (0x8000 - 4)
_copy_fdt:
lw r12, r7, r11 /* r12 = r7 + r11 */
sw r12, r4, r11 /* addr[r4 + r11] = r12 */
addik r11, r11, 4 /* increment counting */
bgtid r3, _copy_fdt /* loop for all entries */
addik r3, r3, -4 /* descrement loop */
no_fdt_arg:
#ifdef CONFIG_MMU
#ifndef CONFIG_CMDLINE_BOOL
/*
* handling command line
* copy command line to __init_end. There is space for storing command line.
*/
or r6, r0, r0 /* incremment */
ori r4, r0, __init_end /* load address of command line */
tophys(r4,r4) /* convert to phys address */
ori r3, r0, COMMAND_LINE_SIZE - 1 /* number of loops */
_copy_command_line:
lbu r2, r5, r6 /* r2=r5+r6 - r5 contain pointer to command line */
sb r2, r4, r6 /* addr[r4+r6]= r2*/
addik r6, r6, 1 /* increment counting */
bgtid r3, _copy_command_line /* loop for all entries */
addik r3, r3, -1 /* descrement loop */
addik r5, r4, 0 /* add new space for command line */
tovirt(r5,r5)
#endif /* CONFIG_CMDLINE_BOOL */
#ifdef NOT_COMPILE
/* save bram context */
or r6, r0, r0 /* incremment */
ori r4, r0, TOPHYS(_bram_load_start) /* save bram context */
ori r3, r0, (LMB_SIZE - 4)
_copy_bram:
lw r7, r0, r6 /* r7 = r0 + r6 */
sw r7, r4, r6 /* addr[r4 + r6] = r7*/
addik r6, r6, 4 /* increment counting */
bgtid r3, _copy_bram /* loop for all entries */
addik r3, r3, -4 /* descrement loop */
#endif
/* We have to turn on the MMU right away. */
/*
* Set up the initial MMU state so we can do the first level of
* kernel initialization. This maps the first 16 MBytes of memory 1:1
* virtual to physical.
*/
nop
addik r3, r0, MICROBLAZE_TLB_SIZE -1 /* Invalidate all TLB entries */
_invalidate:
mts rtlbx, r3
mts rtlbhi, r0 /* flush: ensure V is clear */
mts rtlblo, r0
bgtid r3, _invalidate /* loop for all entries */
addik r3, r3, -1
/* sync */
/* Setup the kernel PID */
mts rpid,r0 /* Load the kernel PID */
nop
bri 4
/*
* We should still be executing code at physical address area
* RAM_BASEADDR at this point. However, kernel code is at
* a virtual address. So, set up a TLB mapping to cover this once
* translation is enabled.
*/
addik r3,r0, CONFIG_KERNEL_START /* Load the kernel virtual address */
tophys(r4,r3) /* Load the kernel physical address */
/* start to do TLB calculation */
addik r12, r0, _end
rsub r12, r3, r12
addik r12, r12, CONFIG_KERNEL_PAD /* that's the pad */
or r9, r0, r0 /* TLB0 = 0 */
or r10, r0, r0 /* TLB1 = 0 */
addik r11, r12, -0x1000000
bgei r11, GT16 /* size is greater than 16MB */
addik r11, r12, -0x0800000
bgei r11, GT8 /* size is greater than 8MB */
addik r11, r12, -0x0400000
bgei r11, GT4 /* size is greater than 4MB */
/* size is less than 4MB */
addik r11, r12, -0x0200000
bgei r11, GT2 /* size is greater than 2MB */
addik r9, r0, 0x0100000 /* TLB0 must be 1MB */
addik r11, r12, -0x0100000
bgei r11, GT1 /* size is greater than 1MB */
/* TLB1 is 0 which is setup above */
bri tlb_end
GT4: /* r11 contains the rest - will be either 1 or 4 */
ori r9, r0, 0x400000 /* TLB0 is 4MB */
bri TLB1
GT16: /* TLB0 is 16MB */
addik r9, r0, 0x1000000 /* means TLB0 is 16MB */
TLB1:
/* must be used r2 because of substract if failed */
addik r2, r11, -0x0400000
bgei r2, GT20 /* size is greater than 16MB */
/* size is >16MB and <20MB */
addik r11, r11, -0x0100000
bgei r11, GT17 /* size is greater than 17MB */
/* kernel is >16MB and < 17MB */
GT1:
addik r10, r0, 0x0100000 /* means TLB1 is 1MB */
bri tlb_end
GT2: /* TLB0 is 0 and TLB1 will be 4MB */
GT17: /* TLB1 is 4MB - kernel size <20MB */
addik r10, r0, 0x0400000 /* means TLB1 is 4MB */
bri tlb_end
GT8: /* TLB0 is still zero that's why I can use only TLB1 */
GT20: /* TLB1 is 16MB - kernel size >20MB */
addik r10, r0, 0x1000000 /* means TLB1 is 16MB */
tlb_end:
/*
* Configure and load two entries into TLB slots 0 and 1.
* In case we are pinning TLBs, these are reserved in by the
* other TLB functions. If not reserving, then it doesn't
* matter where they are loaded.
*/
andi r4,r4,0xfffffc00 /* Mask off the real page number */
ori r4,r4,(TLB_WR | TLB_EX) /* Set the write and execute bits */
/*
* TLB0 is always used - check if is not zero (r9 stores TLB0 value)
* if is use TLB1 value and clear it (r10 stores TLB1 value)
*/
bnei r9, tlb0_not_zero
add r9, r10, r0
add r10, r0, r0
tlb0_not_zero:
/* look at the code below */
ori r30, r0, 0x200
andi r29, r9, 0x100000
bneid r29, 1f
addik r30, r30, 0x80
andi r29, r9, 0x400000
bneid r29, 1f
addik r30, r30, 0x80
andi r29, r9, 0x1000000
bneid r29, 1f
addik r30, r30, 0x80
1:
andi r3,r3,0xfffffc00 /* Mask off the effective page number */
ori r3,r3,(TLB_VALID)
or r3, r3, r30
/* Load tlb_skip size value which is index to first unused TLB entry */
lwi r11, r0, TOPHYS(tlb_skip)
mts rtlbx,r11 /* TLB slow 0 */
mts rtlblo,r4 /* Load the data portion of the entry */
mts rtlbhi,r3 /* Load the tag portion of the entry */
/* Increase tlb_skip size */
addik r11, r11, 1
swi r11, r0, TOPHYS(tlb_skip)
/* TLB1 can be zeroes that's why we not setup it */
beqi r10, jump_over2
/* look at the code below */
ori r30, r0, 0x200
andi r29, r10, 0x100000
bneid r29, 1f
addik r30, r30, 0x80
andi r29, r10, 0x400000
bneid r29, 1f
addik r30, r30, 0x80
andi r29, r10, 0x1000000
bneid r29, 1f
addik r30, r30, 0x80
1:
addk r4, r4, r9 /* previous addr + TLB0 size */
addk r3, r3, r9
andi r3,r3,0xfffffc00 /* Mask off the effective page number */
ori r3,r3,(TLB_VALID)
or r3, r3, r30
lwi r11, r0, TOPHYS(tlb_skip)
mts rtlbx, r11 /* r11 is used from TLB0 */
mts rtlblo,r4 /* Load the data portion of the entry */
mts rtlbhi,r3 /* Load the tag portion of the entry */
/* Increase tlb_skip size */
addik r11, r11, 1
swi r11, r0, TOPHYS(tlb_skip)
jump_over2:
/*
* Load a TLB entry for LMB, since we need access to
* the exception vectors, using a 4k real==virtual mapping.
*/
/* Use temporary TLB_ID for LMB - clear this temporary mapping later */
ori r6, r0, MICROBLAZE_LMB_TLB_ID
mts rtlbx,r6
ori r4,r0,(TLB_WR | TLB_EX)
ori r3,r0,(TLB_VALID | TLB_PAGESZ(PAGESZ_4K))
mts rtlblo,r4 /* Load the data portion of the entry */
mts rtlbhi,r3 /* Load the tag portion of the entry */
/*
* We now have the lower 16 Meg of RAM mapped into TLB entries, and the
* caches ready to work.
*/
turn_on_mmu:
ori r15,r0,start_here
ori r4,r0,MSR_KERNEL_VMS
mts rmsr,r4
nop
rted r15,0 /* enables MMU */
nop
start_here:
#endif /* CONFIG_MMU */
/* Initialize small data anchors */
addik r13, r0, _KERNEL_SDA_BASE_
addik r2, r0, _KERNEL_SDA2_BASE_
/* Initialize stack pointer */
addik r1, r0, init_thread_union + THREAD_SIZE - 4
/* Initialize r31 with current task address */
addik r31, r0, init_task
/*
* Call platform dependent initialize function.
* Please see $(ARCH)/mach-$(SUBARCH)/setup.c for
* the function.
*/
addik r11, r0, machine_early_init
brald r15, r11
nop
#ifndef CONFIG_MMU
addik r15, r0, machine_halt
braid start_kernel
nop
#else
/*
* Initialize the MMU.
*/
bralid r15, mmu_init
nop
/* Go back to running unmapped so we can load up new values
* and change to using our exception vectors.
* On the MicroBlaze, all we invalidate the used TLB entries to clear
* the old 16M byte TLB mappings.
*/
ori r15,r0,TOPHYS(kernel_load_context)
ori r4,r0,MSR_KERNEL
mts rmsr,r4
nop
bri 4
rted r15,0
nop
/* Load up the kernel context */
kernel_load_context:
ori r5, r0, MICROBLAZE_LMB_TLB_ID
mts rtlbx,r5
nop
mts rtlbhi,r0
nop
addi r15, r0, machine_halt
ori r17, r0, start_kernel
ori r4, r0, MSR_KERNEL_VMS
mts rmsr, r4
nop
rted r17, 0 /* enable MMU and jump to start_kernel */
nop
#endif /* CONFIG_MMU */
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