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linux/arch/arm/kernel/head-nommu.S
Vladimir Murzin a0995c0805 ARM: 8708/1: NOMMU: Rework MPU to be mostly done in C 
Currently, there are several issues with how MPU is setup:

 1. We won't boot if MPU is missing
 2. We won't boot if use XIP
 3. Further extension of MPU setup requires asm skills

The 1st point can be relaxed, so we can continue with boot CPU even if
MPU is missed and fail boot for secondaries only. To address the 2nd
point we could create region covering CONFIG_XIP_PHYS_ADDR - _end and
that might work for the first stage of MPU enable, but due to MPU's
alignment requirement we could cover too much, IOW we need more
flexibility in how we're partitioning memory regions... and it'd be
hardly possible to archive because of the 3rd point.

This patch is trying to address 1st and 3rd issues and paves the path
for 2nd and further improvements.

The most visible change introduced with this patch is that we start
using mpu_rgn_info array (as it was supposed?), so change in MPU setup
done by boot CPU is recorded there and feed to secondaries. It
allows us to keep minimal region setup for boot CPU and do the rest in
C. Since we start programming MPU regions in C evaluation of MPU
constrains (number of regions supported and minimal region order) can
be done once, which in turn open possibility to free-up "probe"
region early.

Tested-by: Szemző András <sza@esh.hu>
Tested-by: Alexandre TORGUE <alexandre.torgue@st.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
2017-10-23 16:58:59 +01:00

309 lines
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/*
* linux/arch/arm/kernel/head-nommu.S
*
* Copyright (C) 1994-2002 Russell King
* Copyright (C) 2003-2006 Hyok S. Choi
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Common kernel startup code (non-paged MM)
*
*/
#include <linux/linkage.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <asm/assembler.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>
#include <asm/memory.h>
#include <asm/cp15.h>
#include <asm/thread_info.h>
#include <asm/v7m.h>
#include <asm/mpu.h>
#include <asm/page.h>
/*
* Kernel startup entry point.
* ---------------------------
*
* This is normally called from the decompressor code. The requirements
* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
* r1 = machine nr.
*
* See linux/arch/arm/tools/mach-types for the complete list of machine
* numbers for r1.
*
*/
__HEAD
#ifdef CONFIG_CPU_THUMBONLY
.thumb
ENTRY(stext)
#else
.arm
ENTRY(stext)
THUMB( badr r9, 1f ) @ Kernel is always entered in ARM.
THUMB( bx r9 ) @ If this is a Thumb-2 kernel,
THUMB( .thumb ) @ switch to Thumb now.
THUMB(1: )
#endif
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
@ and irqs disabled
#if defined(CONFIG_CPU_CP15)
mrc p15, 0, r9, c0, c0 @ get processor id
#elif defined(CONFIG_CPU_V7M)
ldr r9, =BASEADDR_V7M_SCB
ldr r9, [r9, V7M_SCB_CPUID]
#else
ldr r9, =CONFIG_PROCESSOR_ID
#endif
bl __lookup_processor_type @ r5=procinfo r9=cpuid
movs r10, r5 @ invalid processor (r5=0)?
beq __error_p @ yes, error 'p'
#ifdef CONFIG_ARM_MPU
/* Calculate the size of a region covering just the kernel */
ldr r5, =PLAT_PHYS_OFFSET @ Region start: PHYS_OFFSET
ldr r6, =(_end) @ Cover whole kernel
sub r6, r6, r5 @ Minimum size of region to map
clz r6, r6 @ Region size must be 2^N...
rsb r6, r6, #31 @ ...so round up region size
lsl r6, r6, #MPU_RSR_SZ @ Put size in right field
orr r6, r6, #(1 << MPU_RSR_EN) @ Set region enabled bit
bl __setup_mpu
#endif
badr lr, 1f @ return (PIC) address
ldr r12, [r10, #PROCINFO_INITFUNC]
add r12, r12, r10
ret r12
1: bl __after_proc_init
b __mmap_switched
ENDPROC(stext)
#ifdef CONFIG_SMP
.text
ENTRY(secondary_startup)
/*
* Common entry point for secondary CPUs.
*
* Ensure that we're in SVC mode, and IRQs are disabled. Lookup
* the processor type - there is no need to check the machine type
* as it has already been validated by the primary processor.
*/
setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9
#ifndef CONFIG_CPU_CP15
ldr r9, =CONFIG_PROCESSOR_ID
#else
mrc p15, 0, r9, c0, c0 @ get processor id
#endif
bl __lookup_processor_type @ r5=procinfo r9=cpuid
movs r10, r5 @ invalid processor?
beq __error_p @ yes, error 'p'
ldr r7, __secondary_data
#ifdef CONFIG_ARM_MPU
/* Use MPU region info supplied by __cpu_up */
ldr r6, [r7] @ get secondary_data.mpu_rgn_info
bl __secondary_setup_mpu @ Initialize the MPU
#endif
badr lr, 1f @ return (PIC) address
ldr r12, [r10, #PROCINFO_INITFUNC]
add r12, r12, r10
ret r12
1: bl __after_proc_init
ldr sp, [r7, #12] @ set up the stack pointer
mov fp, #0
b secondary_start_kernel
ENDPROC(secondary_startup)
.type __secondary_data, %object
__secondary_data:
.long secondary_data
#endif /* CONFIG_SMP */
/*
* Set the Control Register and Read the process ID.
*/
__after_proc_init:
#ifdef CONFIG_CPU_CP15
/*
* CP15 system control register value returned in r0 from
* the CPU init function.
*/
#if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
orr r0, r0, #CR_A
#else
bic r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
bic r0, r0, #CR_C
#endif
#ifdef CONFIG_CPU_BPREDICT_DISABLE
bic r0, r0, #CR_Z
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
bic r0, r0, #CR_I
#endif
mcr p15, 0, r0, c1, c0, 0 @ write control reg
#elif defined (CONFIG_CPU_V7M)
/* For V7M systems we want to modify the CCR similarly to the SCTLR */
#ifdef CONFIG_CPU_DCACHE_DISABLE
bic r0, r0, #V7M_SCB_CCR_DC
#endif
#ifdef CONFIG_CPU_BPREDICT_DISABLE
bic r0, r0, #V7M_SCB_CCR_BP
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
bic r0, r0, #V7M_SCB_CCR_IC
#endif
movw r3, #:lower16:(BASEADDR_V7M_SCB + V7M_SCB_CCR)
movt r3, #:upper16:(BASEADDR_V7M_SCB + V7M_SCB_CCR)
str r0, [r3]
#endif /* CONFIG_CPU_CP15 elif CONFIG_CPU_V7M */
ret lr
ENDPROC(__after_proc_init)
.ltorg
#ifdef CONFIG_ARM_MPU
/* Set which MPU region should be programmed */
.macro set_region_nr tmp, rgnr
mov \tmp, \rgnr @ Use static region numbers
mcr p15, 0, \tmp, c6, c2, 0 @ Write RGNR
.endm
/* Setup a single MPU region, either D or I side (D-side for unified) */
.macro setup_region bar, acr, sr, side = MPU_DATA_SIDE
mcr p15, 0, \bar, c6, c1, (0 + \side) @ I/DRBAR
mcr p15, 0, \acr, c6, c1, (4 + \side) @ I/DRACR
mcr p15, 0, \sr, c6, c1, (2 + \side) @ I/DRSR
.endm
/*
* Setup the MPU and initial MPU Regions. We create the following regions:
* Region 0: Use this for probing the MPU details, so leave disabled.
* Region 1: Background region - covers the whole of RAM as strongly ordered
* Region 2: Normal, Shared, cacheable for RAM. From PHYS_OFFSET, size from r6
* Region 3: Normal, shared, inaccessible from PL0 to protect the vectors page
*
* r6: Value to be written to DRSR (and IRSR if required) for MPU_RAM_REGION
*/
ENTRY(__setup_mpu)
/* Probe for v7 PMSA compliance */
mrc p15, 0, r0, c0, c1, 4 @ Read ID_MMFR0
and r0, r0, #(MMFR0_PMSA) @ PMSA field
teq r0, #(MMFR0_PMSAv7) @ PMSA v7
bxne lr
/* Determine whether the D/I-side memory map is unified. We set the
* flags here and continue to use them for the rest of this function */
mrc p15, 0, r0, c0, c0, 4 @ MPUIR
ands r5, r0, #MPUIR_DREGION_SZMASK @ 0 size d region => No MPU
bxeq lr
tst r0, #MPUIR_nU @ MPUIR_nU = 0 for unified
/* Setup second region first to free up r6 */
set_region_nr r0, #MPU_RAM_REGION
isb
/* Full access from PL0, PL1, shared for CONFIG_SMP, cacheable */
ldr r0, =PLAT_PHYS_OFFSET @ RAM starts at PHYS_OFFSET
ldr r5,=(MPU_AP_PL1RW_PL0RW | MPU_RGN_NORMAL)
setup_region r0, r5, r6, MPU_DATA_SIDE @ PHYS_OFFSET, shared, enabled
beq 1f @ Memory-map not unified
setup_region r0, r5, r6, MPU_INSTR_SIDE @ PHYS_OFFSET, shared, enabled
1: isb
/* First/background region */
set_region_nr r0, #MPU_BG_REGION
isb
/* Execute Never, strongly ordered, inaccessible to PL0, rw PL1 */
mov r0, #0 @ BG region starts at 0x0
ldr r5,=(MPU_ACR_XN | MPU_RGN_STRONGLY_ORDERED | MPU_AP_PL1RW_PL0NA)
mov r6, #MPU_RSR_ALL_MEM @ 4GB region, enabled
setup_region r0, r5, r6, MPU_DATA_SIDE @ 0x0, BG region, enabled
beq 2f @ Memory-map not unified
setup_region r0, r5, r6, MPU_INSTR_SIDE @ 0x0, BG region, enabled
2: isb
/* Enable the MPU */
mrc p15, 0, r0, c1, c0, 0 @ Read SCTLR
bic r0, r0, #CR_BR @ Disable the 'default mem-map'
orr r0, r0, #CR_M @ Set SCTRL.M (MPU on)
mcr p15, 0, r0, c1, c0, 0 @ Enable MPU
isb
ret lr
ENDPROC(__setup_mpu)
#ifdef CONFIG_SMP
/*
* r6: pointer at mpu_rgn_info
*/
ENTRY(__secondary_setup_mpu)
/* Probe for v7 PMSA compliance */
mrc p15, 0, r0, c0, c1, 4 @ Read ID_MMFR0
and r0, r0, #(MMFR0_PMSA) @ PMSA field
teq r0, #(MMFR0_PMSAv7) @ PMSA v7
bne __error_p
/* Determine whether the D/I-side memory map is unified. We set the
* flags here and continue to use them for the rest of this function */
mrc p15, 0, r0, c0, c0, 4 @ MPUIR
ands r5, r0, #MPUIR_DREGION_SZMASK @ 0 size d region => No MPU
beq __error_p
ldr r4, [r6, #MPU_RNG_INFO_USED]
mov r5, #MPU_RNG_SIZE
add r3, r6, #MPU_RNG_INFO_RNGS
mla r3, r4, r5, r3
1:
tst r0, #MPUIR_nU @ MPUIR_nU = 0 for unified
sub r3, r3, #MPU_RNG_SIZE
sub r4, r4, #1
set_region_nr r0, r4
isb
ldr r0, [r3, #MPU_RGN_DRBAR]
ldr r6, [r3, #MPU_RGN_DRSR]
ldr r5, [r3, #MPU_RGN_DRACR]
setup_region r0, r5, r6, MPU_DATA_SIDE
beq 2f
setup_region r0, r5, r6, MPU_INSTR_SIDE
2: isb
mrc p15, 0, r0, c0, c0, 4 @ Reevaluate the MPUIR
cmp r4, #0
bgt 1b
/* Enable the MPU */
mrc p15, 0, r0, c1, c0, 0 @ Read SCTLR
bic r0, r0, #CR_BR @ Disable the 'default mem-map'
orr r0, r0, #CR_M @ Set SCTRL.M (MPU on)
mcr p15, 0, r0, c1, c0, 0 @ Enable MPU
isb
ret lr
ENDPROC(__secondary_setup_mpu)
#endif /* CONFIG_SMP */
#endif /* CONFIG_ARM_MPU */
#include "head-common.S"
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