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

From: [email-masked] (Jon Mason)
Date: Thu, 15 Oct 2015 17:17:03 -0400

On Thu, Oct 15, 2015 at 11:12:09PM +0200, Hauke Mehrtens wrote:
> On 10/15/2015 06:10 PM, Kapil Hali wrote:
> > 
> > 
> > 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.
> 
> Which SoC are affected by this BOOTROM bug?

53012 is the one I am seeing.  Not seeing it on 4708 (and assuming it is
not present on 4709).  Internally, we do the ugly bug workaround on
all Northstar SoCs.  The workaround is not acceptable upstream, so I
am not pushing it. :)

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.
> >>
> > 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
> > 
>