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ARM: shmobile: rcar-gen2: Make sure CNTVOFF is initialized on CA7/15 

On Cortex-A7, the arch timer CNTVOFF register is uninitialized.
Ideally it should be initialized by the boot loader, but it isn't.

For the boot CPU, CNTVOFF is initialized by Linux since commit
9ce3fa6816 ("ARM: shmobile: rcar-gen2: Add CA7 arch_timer
initialization for r8a7794").
For secondary CPU cores, no such initialization is done.

Hence when enabling SMP on r8a7794, the kernel log is spammed with:

    WARNING: Underflow in clocksource 'arch_sys_counter' observed, time update ignored.
	     Please report this, consider using a different clocksource, if possible.
	     Your kernel is probably still fine.

As Marc Zyngier pointed out that Cortex-A15 and Cortex-A7 are similar with
respect to CNTVOFF, we have been very lucky this just worked on R-Car
Gen2 SoCs with Cortex-A15 cores.

To fix this:
  - Move the existing inline asm code to initialize CNTVOFF to an
    assembler source file (adding comments and replacing hardcoded
    constants by definitions in the process), so it can be reused,
  - Perform the initialization of CNTVOFF on the boot CPU (Cortex-A15 or
    Cortex-A7) on all R-Car Gen2 and RZ/G1 parts,
  - Wrap the standard secondary_startup() routine inside a routine which
    initializes CNTVOFF.

Based on patches by Hisashi Nakamura in the BSP.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
This commit is contained in:
Geert Uytterhoeven 2017-09-01 10:37:45 +02:00 committed by Simon Horman
parent c5d43be52e
commit 3fd45a136f
5 changed files with 43 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm/mach-shmobile/Makefile
View File

@ -22,6 +22,7 @@ cpu-y := platsmp.o headsmp.o
# Shared SoC family objects
obj-$(CONFIG_ARCH_RCAR_GEN2) += setup-rcar-gen2.o platsmp-apmu.o $(cpu-y)
CFLAGS_setup-rcar-gen2.o += -march=armv7-a
obj-$(CONFIG_ARCH_RCAR_GEN2) += headsmp-apmu.o
obj-$(CONFIG_ARCH_R8A7790) += regulator-quirk-rcar-gen2.o
obj-$(CONFIG_ARCH_R8A7791) += regulator-quirk-rcar-gen2.o
obj-$(CONFIG_ARCH_R8A7793) += regulator-quirk-rcar-gen2.o

2
arch/arm/mach-shmobile/common.h
View File

@ -1,6 +1,7 @@
#ifndef __ARCH_MACH_COMMON_H
#define __ARCH_MACH_COMMON_H
extern void shmobile_init_cntvoff(void);
extern void shmobile_init_delay(void);
extern void shmobile_boot_vector(void);
extern unsigned long shmobile_boot_fn;
@ -11,6 +12,7 @@ extern void shmobile_smp_hook(unsigned int cpu, unsigned long fn,
unsigned long arg);
extern bool shmobile_smp_cpu_can_disable(unsigned int cpu);
extern bool shmobile_smp_init_fallback_ops(void);
extern void shmobile_boot_apmu(void);
extern void shmobile_boot_scu(void);
extern void shmobile_smp_scu_prepare_cpus(phys_addr_t scu_base_phys,
unsigned int max_cpus);

37
arch/arm/mach-shmobile/headsmp-apmu.S Normal file
View File

@ -0,0 +1,37 @@
/*
* SMP support for APMU based systems with Cortex A7/A15
*
* Copyright (C) 2014 Renesas Electronics Corporation
*
* 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.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
ENTRY(shmobile_init_cntvoff)
/*
* CNTVOFF has to be initialized either from non-secure Hypervisor
* mode or secure Monitor mode with SCR.NS==1. If TrustZone is enabled
* then it should be handled by the secure code
*/
cps #MON_MODE
mrc p15, 0, r1, c1, c1, 0 /* Get Secure Config */
orr r0, r1, #1
mcr p15, 0, r0, c1, c1, 0 /* Set Non Secure bit */
instr_sync
mov r0, #0
mcrr p15, 4, r0, r0, c14 /* CNTVOFF = 0 */
instr_sync
mcr p15, 0, r1, c1, c1, 0 /* Set Secure bit */
instr_sync
cps #SVC_MODE
ret lr
ENDPROC(shmobile_init_cntvoff)
ENTRY(shmobile_boot_apmu)
bl shmobile_init_cntvoff
b secondary_startup
ENDPROC(shmobile_boot_apmu)

2
arch/arm/mach-shmobile/platsmp-apmu.c
View File

@ -204,7 +204,7 @@ void __init shmobile_smp_apmu_prepare_cpus(unsigned int max_cpus,
int shmobile_smp_apmu_boot_secondary(unsigned int cpu, struct task_struct *idle)
{
/* For this particular CPU register boot vector */
shmobile_smp_hook(cpu, __pa_symbol(secondary_startup), 0);
shmobile_smp_hook(cpu, __pa_symbol(shmobile_boot_apmu), 0);
return apmu_wrap(cpu, apmu_power_on);
}

20
arch/arm/mach-shmobile/setup-rcar-gen2.c
View File

@ -70,28 +70,12 @@ void __init rcar_gen2_timer_init(void)
void __iomem *base;
u32 freq;
shmobile_init_cntvoff();
if (of_machine_is_compatible("renesas,r8a7745") ||
of_machine_is_compatible("renesas,r8a7792") ||
of_machine_is_compatible("renesas,r8a7794")) {
freq = 260000000 / 8; /* ZS / 8 */
/* CNTVOFF has to be initialized either from non-secure
* Hypervisor mode or secure Monitor mode with SCR.NS==1.
* If TrustZone is enabled then it should be handled by the
* secure code.
*/
asm volatile(
" cps 0x16\n"
" mrc p15, 0, r1, c1, c1, 0\n"
" orr r0, r1, #1\n"
" mcr p15, 0, r0, c1, c1, 0\n"
" isb\n"
" mov r0, #0\n"
" mcrr p15, 4, r0, r0, c14\n"
" isb\n"
" mcr p15, 0, r1, c1, c1, 0\n"
" isb\n"
" cps 0x13\n"
: : : "r0", "r1");
} else {
/* At Linux boot time the r8a7790 arch timer comes up
* with the counter disabled. Moreover, it may also report