Re: [PATCH 3/3] ARM: BCM: Add SMP support for Broadcom NSP

From: Kapil Hali
Date: Thu Oct 15 2015 - 12:11:01 EST



On 10/15/2015 3:56 AM, Hauke Mehrtens wrote:
> On 10/14/2015 07:47 PM, Kapil Hali wrote:
>> Add SMP support for Broadcom's Northstar Plus SoC,
>> cpu enable method and pen_release procedures. This
>> changes also consolidates iProc family's - BCM NSP
>> and BCM Kona, SMP handling in a common file.
>
> This will probably also work on normal Northstar CPUs without changes.
>
I think, it should work for most of the variants of Northstar family,
except for those which have a BOOTROM bug.

>> Northstar Plus SoC is based on ARM Cortex-A9
>> revision r3p0 which requires configuration for ARM
>> Errata 764369 for SMP. This change adds the needed
>> configuration option.
>>
>> Signed-off-by: Kapil Hali <kapilh@xxxxxxxxxxxx>
>> ---
>> arch/arm/mach-bcm/Kconfig | 2 +
>> arch/arm/mach-bcm/Makefile | 8 +-
>> arch/arm/mach-bcm/bcm_nsp.h | 19 ++++
>> arch/arm/mach-bcm/headsmp.S | 37 ++++++++
>> arch/arm/mach-bcm/{kona_smp.c => platsmp.c} | 142 ++++++++++++++++++++++++++--
>> 5 files changed, 197 insertions(+), 11 deletions(-)
>> create mode 100644 arch/arm/mach-bcm/bcm_nsp.h
>> create mode 100644 arch/arm/mach-bcm/headsmp.S
>> rename arch/arm/mach-bcm/{kona_smp.c => platsmp.c} (63%)
>>
>> diff --git a/arch/arm/mach-bcm/Kconfig b/arch/arm/mach-bcm/Kconfig
>> index 1679fa4..2e9dbb5 100644
>> --- a/arch/arm/mach-bcm/Kconfig
>> +++ b/arch/arm/mach-bcm/Kconfig
>> @@ -40,6 +40,8 @@ config ARCH_BCM_NSP
>> select ARCH_BCM_IPROC
>> select ARM_ERRATA_754322
>> select ARM_ERRATA_775420
>> + select ARM_ERRATA_764369 if SMP
>> + select HAVE_SMP
>> help
>> Support for Broadcom Northstar Plus SoC.
>> Broadcom Northstar Plus family of SoCs are used for switching control
>> diff --git a/arch/arm/mach-bcm/Makefile b/arch/arm/mach-bcm/Makefile
>> index 892261f..36a4ca30 100644
>> --- a/arch/arm/mach-bcm/Makefile
>> +++ b/arch/arm/mach-bcm/Makefile
>> @@ -14,7 +14,11 @@
>> obj-$(CONFIG_ARCH_BCM_CYGNUS) += bcm_cygnus.o
>>
>> # Northstar Plus
>> -obj-$(CONFIG_ARCH_BCM_NSP) += bcm_nsp.o
>> +obj-$(CONFIG_ARCH_BCM_NSP) += bcm_nsp.o
>> +
>> +ifeq ($(CONFIG_ARCH_BCM_NSP),y)
>> +obj-$(CONFIG_SMP) += headsmp.o platsmp.o
>> +endif
>>
>> # BCM281XX
>> obj-$(CONFIG_ARCH_BCM_281XX) += board_bcm281xx.o
>> @@ -23,7 +27,7 @@ obj-$(CONFIG_ARCH_BCM_281XX) += board_bcm281xx.o
>> obj-$(CONFIG_ARCH_BCM_21664) += board_bcm21664.o
>>
>> # BCM281XX and BCM21664 SMP support
>> -obj-$(CONFIG_ARCH_BCM_MOBILE_SMP) += kona_smp.o
>> +obj-$(CONFIG_ARCH_BCM_MOBILE_SMP) += platsmp.o
>>
>> # BCM281XX and BCM21664 L2 cache control
>> obj-$(CONFIG_ARCH_BCM_MOBILE_L2_CACHE) += kona_l2_cache.o
>> diff --git a/arch/arm/mach-bcm/bcm_nsp.h b/arch/arm/mach-bcm/bcm_nsp.h
>> new file mode 100644
>> index 0000000..58e1e80
>> --- /dev/null
>> +++ b/arch/arm/mach-bcm/bcm_nsp.h
>> @@ -0,0 +1,19 @@
>> +/*
>> + * Copyright (C) 2015 Broadcom Corporation
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License as
>> + * published by the Free Software Foundation version 2.
>> + *
>> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
>> + * kind, whether express or implied; without even the implied warranty
>> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#ifndef __BCM_NSP_H
>> +#define __BCM_NSP_H
>> +
>> +extern void nsp_secondary_startup(void);
>> +
>> +#endif /* __BCM_NSP_H */
>> diff --git a/arch/arm/mach-bcm/headsmp.S b/arch/arm/mach-bcm/headsmp.S
>> new file mode 100644
>> index 0000000..0da13b2
>> --- /dev/null
>> +++ b/arch/arm/mach-bcm/headsmp.S
>> @@ -0,0 +1,37 @@
>> +/*
>> + * Copyright (C) 2015 Broadcom Corporation
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License as
>> + * published by the Free Software Foundation version 2.
>> + *
>> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
>> + * kind, whether express or implied; without even the implied warranty
>> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/linkage.h>
>> +
>> +/*
>> + * iProc specific entry point for secondary CPUs. This provides
>> + * a "holding pen" into which all secondary cores are held until
>> + * we are ready for them to initialise.
>> + */
>> +ENTRY(nsp_secondary_startup)
>> + mrc p15, 0, r0, c0, c0, 5
>> + and r0, r0, #15
>> + adr r4, 1f
>> + ldmia r4, {r5, r6}
>> + sub r4, r4, r5
>> + add r6, r6, r4
>> +pen: ldr r7, [r6]
>> + cmp r7, r0
>> + bne pen
>> +
>> + b secondary_startup
>> +
>> +1: .long .
>> + .long pen_release
>> +
>> +ENDPROC(nsp_secondary_startup)
>> diff --git a/arch/arm/mach-bcm/kona_smp.c b/arch/arm/mach-bcm/platsmp.c
>> similarity index 63%
>> rename from arch/arm/mach-bcm/kona_smp.c
>> rename to arch/arm/mach-bcm/platsmp.c
>> index 66a0465..619030e 100644
>> --- a/arch/arm/mach-bcm/kona_smp.c
>> +++ b/arch/arm/mach-bcm/platsmp.c
>> @@ -1,5 +1,5 @@
>> /*
>> - * Copyright (C) 2014 Broadcom Corporation
>> + * Copyright (C) 2014-2015 Broadcom Corporation
>> * Copyright 2014 Linaro Limited
>> *
>> * This program is free software; you can redistribute it and/or
>> @@ -12,16 +12,23 @@
>> * GNU General Public License for more details.
>> */
>>
>> -#include <linux/init.h>
>> +#include <linux/cpumask.h>
>> +#include <linux/delay.h>
>> #include <linux/errno.h>
>> +#include <linux/init.h>
>> #include <linux/io.h>
>> +#include <linux/jiffies.h>
>> #include <linux/of.h>
>> #include <linux/sched.h>
>> +#include <linux/smp.h>
>>
>> +#include <asm/cacheflush.h>
>> #include <asm/smp.h>
>> #include <asm/smp_plat.h>
>> #include <asm/smp_scu.h>
>>
>> +#include "bcm_nsp.h"
>> +
>> /* Size of mapped Cortex A9 SCU address space */
>> #define CORTEX_A9_SCU_SIZE 0x58
>>
>> @@ -34,6 +41,24 @@
>> /* I/O address of register used to coordinate secondary core startup */
>> static u32 secondary_boot;
>>
>> +static DEFINE_SPINLOCK(boot_lock);
>> +
>> +/*
>> + * Write pen_release in a way that is guaranteed to be visible to all
>> + * observers, irrespective of whether they're taking part in coherency
>> + * or not. This is necessary for the hotplug code to work reliably.
>> + */
>> +static void write_pen_release(int val)
>> +{
>> + pen_release = val;
>> + /*
>> + * Ensure write to pen_release is visible to the other cores,
>> + * here - primary core
>> + */
>> + smp_wmb();
>> + sync_cache_w(&pen_release);
>> +}
>> +
>> /*
>> * Enable the Cortex A9 Snoop Control Unit
>> *
>> @@ -75,6 +100,51 @@ static int __init scu_a9_enable(void)
>> return 0;
>> }
>>
>> +static int nsp_write_lut(void (*secondary_startup) (void))
>> +{
>> + void __iomem *sku_rom_lut;
>> + phys_addr_t secondary_startup_phy;
>> +
>> + if (!secondary_boot) {
>> + pr_warn("required secondary boot register not specified\n");
>> + return -EINVAL;
>> + }
>> +
>> + sku_rom_lut = ioremap_nocache((phys_addr_t)secondary_boot,
>> + sizeof(secondary_boot));
>> + if (!sku_rom_lut) {
>> + pr_warn("unable to ioremap SKU-ROM LUT register\n");
>> + return -ENOMEM;
>> + }
>> +
>> + secondary_startup_phy = virt_to_phys(secondary_startup);
>> + BUG_ON(secondary_startup_phy > (phys_addr_t)U32_MAX);
>> +
>> + writel_relaxed(secondary_startup_phy, sku_rom_lut);
>> + /*
>> + * Ensure the write is visible to the secondary core.
>> + */
>> + smp_wmb();
>> +
>> + iounmap(sku_rom_lut);
>> +
>> + return 0;
>> +}
>> +
>> +static void nsp_secondary_init(unsigned int cpu)
>> +{
>> + /*
>> + * Let the primary cpu know we are out of holding pen.
>> + */
>> + write_pen_release(-1);
>> +
>> + /*
>> + * Synchronise with the boot thread.
>> + */
>> + spin_lock(&boot_lock);
>> + spin_unlock(&boot_lock);
>> +}
>> +
>> static void __init bcm_smp_prepare_cpus(unsigned int max_cpus)
>> {
>> static cpumask_t only_cpu_0 = { CPU_BITS_CPU0 };
>> @@ -95,11 +165,11 @@ static void __init bcm_smp_prepare_cpus(unsigned int max_cpus)
>> /*
>> * Our secondary enable method requires a "secondary-boot-reg"
>> * property to specify a register address used to request the
>> - * ROM code boot a secondary code. If we have any trouble
>> + * ROM code boot a secondary core. If we have any trouble
>> * getting this we fall back to uniprocessor mode.
>> */
>> if (of_property_read_u32(node, OF_SECONDARY_BOOT, &secondary_boot)) {
>> - pr_err("%s: missing/invalid " OF_SECONDARY_BOOT " property\n",
>> + pr_warn("%s: missing/invalid " OF_SECONDARY_BOOT " property\n",
>> node->name);
>> ret = -ENOENT; /* Arrange to disable SMP */
>> goto out;
>> @@ -115,7 +185,6 @@ out:
>> of_node_put(node);
>> if (ret) {
>> /* Update the CPU present map to reflect uniprocessor mode */
>> - BUG_ON(ret != -ENOENT);
>> pr_warn("disabling SMP\n");
>> init_cpu_present(&only_cpu_0);
>> }
>> @@ -139,7 +208,7 @@ out:
>> * - Wait for the secondary boot register to be re-written, which
>> * indicates the secondary core has started.
>> */
>> -static int bcm_boot_secondary(unsigned int cpu, struct task_struct *idle)
>> +static int kona_boot_secondary(unsigned int cpu, struct task_struct *idle)
>> {
>> void __iomem *boot_reg;
>> phys_addr_t boot_func;
>> @@ -162,7 +231,7 @@ static int bcm_boot_secondary(unsigned int cpu, struct task_struct *idle)
>> boot_reg = ioremap_nocache((phys_addr_t)secondary_boot, sizeof(u32));
>> if (!boot_reg) {
>> pr_err("unable to map boot register for cpu %u\n", cpu_id);
>> - return -ENOSYS;
>> + return -ENOMEM;
>> }
>>
>> /*
>> @@ -191,12 +260,67 @@ static int bcm_boot_secondary(unsigned int cpu, struct task_struct *idle)
>>
>> pr_err("timeout waiting for cpu %u to start\n", cpu_id);
>>
>> - return -ENOSYS;
>> + return -ENXIO;
>> +}
>> +
>> +static int nsp_boot_secondary(unsigned int cpu, struct task_struct *idle)
>> +{
>> + unsigned long timeout;
>> + int ret;
>> +
>> + /*
>> + * After wake up, secondary core branches to the startup
>> + * address programmed at SKU ROM LUT location.
>> + */
>> + ret = nsp_write_lut(nsp_secondary_startup);
>> + if (ret) {
>> + pr_err("unable to write startup addr to SKU ROM LUT\n");
>> + goto out;
>> + }
>> +
>> + /*
>> + * The secondary processor is waiting to be released from
>> + * the holding pen - release it, then wait for it to flag
>> + * that it has been released by resetting pen_release.
>> + */
>> + spin_lock(&boot_lock);
>> +
>> + write_pen_release(cpu_logical_map(cpu));
>> + /*
>> + * Send an Event to wake up the secondary core which is in
>> + * WFE state. Updated pen_release should also be visible to
>> + * the secondary core.
>> + */
>> + dsb_sev();
>> +
>> + timeout = jiffies + (1 * HZ);
>> + while (time_before(jiffies, timeout)) {
>> + /* Make sure loads on other CPU is visible */
>> + smp_rmb();
>> + if (pen_release == -1)
>> + break;
>> +
>> + udelay(10);
>> + }
>> +
>> + spin_unlock(&boot_lock);
>
> Why is this boot_lock needed? As far as I understand it asserts that
> both CPUs leave nsp_boot_secondary() and nsp_secondary_init() at the
> same time.
>
It makes sure secondary cpu doesn't run away before primary cpu
recognizes the presence of secondary cpu, it is a way of
synchronization between primary and secondary cpu. This is the
method used across many SoCs.
>> +
>> + ret = pen_release != -1 ? -ENXIO : 0;
>> +
>> +out:
>> + return ret;
>> }
>>
>> static struct smp_operations bcm_smp_ops __initdata = {
>> .smp_prepare_cpus = bcm_smp_prepare_cpus,
>> - .smp_boot_secondary = bcm_boot_secondary,
>> + .smp_boot_secondary = kona_boot_secondary,
>> };
>> CPU_METHOD_OF_DECLARE(bcm_smp_bcm281xx, "brcm,bcm11351-cpu-method",
>> &bcm_smp_ops);
>> +
>> +struct smp_operations nsp_smp_ops __initdata = {
>> + .smp_prepare_cpus = bcm_smp_prepare_cpus,
>> + .smp_secondary_init = nsp_secondary_init,
>> + .smp_boot_secondary = nsp_boot_secondary,
>> +};
>> +CPU_METHOD_OF_DECLARE(bcm_smp_nsp, "brcm,bcm-nsp-smp", &nsp_smp_ops);
>>
>
Thanks,
Kapil
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