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

From: [email-masked] (Jon Mason)
Date: Wed, 14 Oct 2015 18:40:04 -0400

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.

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 <[email-masked]>
> > ---
> >  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);
> > 
>