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

From: Jon Mason
Date: Thu Oct 15 2015 - 11:49:45 EST

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On Wed, Oct 14, 2015 at 06:40:04PM -0400, Jon Mason wrote:
> On Thu, Oct 15, 2015 at 12:26:25AM +0200, 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 all that needs to be changed is adding to
> arch/arm/boot/dts/bcm4708.dts
>
> + enable-method = "brcm,bcm-nsp-smp";
> + secondary-boot-reg = <0xffff0400>;
>
> But I have not been able to confirm that yet.

I was able to confirm it on my BCM94708 SVK. I'll send out the patch
which enables it shortly.

Thanks,
Jon

>
> Thanks,
> Jon
>
> >
> > > 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.
> >
> > > +
> > > + 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);
> > >
> >
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