Subject: [PATCH v3 09/15] ARM: vexpress: introduce DCSCB support

From: [email-masked] (Santosh Shilimkar)
Date: Fri, 1 Feb 2013 11:20:04 +0530

On Tuesday 29 January 2013 01:21 PM, Nicolas Pitre wrote:
> This adds basic CPU and cluster reset controls on RTSM for the
> A15x4-A7x4 model configuration using the Dual Cluster System
> Configuration Block (DCSCB).
>
> The cache coherency interconnect (CCI) is not handled yet.
>
> Signed-off-by: Nicolas Pitre <[email-masked]>
> ---
>   arch/arm/mach-vexpress/Kconfig  |   8 ++
>   arch/arm/mach-vexpress/Makefile |   1 +
>   arch/arm/mach-vexpress/dcscb.c  | 159 ++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 168 insertions(+)
>   create mode 100644 arch/arm/mach-vexpress/dcscb.c
>
> diff --git a/arch/arm/mach-vexpress/Kconfig b/arch/arm/mach-vexpress/Kconfig
> index 52d315b792..f3f92b120a 100644
> --- a/arch/arm/mach-vexpress/Kconfig
> +++ b/arch/arm/mach-vexpress/Kconfig
> @@ -52,4 +52,12 @@ config ARCH_VEXPRESS_CORTEX_A5_A9_ERRATA
>   config ARCH_VEXPRESS_CA9X4
>   	bool "Versatile Express Cortex-A9x4 tile"
>
> +config ARCH_VEXPRESS_DCSCB
> +	bool "Dual Cluster System Control Block (DCSCB) support"
> +	depends on CLUSTER_PM
> +	help
> +	  Support for the Dual Cluster System Configuration Block (DCSCB).
> +	  This is needed to provide CPU and cluster power management
> +	  on RTSM.
> +
>   endmenu
> diff --git a/arch/arm/mach-vexpress/Makefile b/arch/arm/mach-vexpress/Makefile
> index 80b64971fb..2253644054 100644
> --- a/arch/arm/mach-vexpress/Makefile
> +++ b/arch/arm/mach-vexpress/Makefile
> @@ -6,5 +6,6 @@ ccflags-$(CONFIG_ARCH_MULTIPLATFORM) := -I$(srctree)/$(src)/include \
>
>   obj-y					:= v2m.o reset.o
>   obj-$(CONFIG_ARCH_VEXPRESS_CA9X4)	+= ct-ca9x4.o
> +obj-$(CONFIG_ARCH_VEXPRESS_DCSCB)	+= dcscb.o
>   obj-$(CONFIG_SMP)			+= platsmp.o
>   obj-$(CONFIG_HOTPLUG_CPU)		+= hotplug.o
> diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c
> new file mode 100644
> index 0000000000..677ced9efc
> --- /dev/null
> +++ b/arch/arm/mach-vexpress/dcscb.c
> @@ -0,0 +1,159 @@
> +/*
> + * arch/arm/mach-vexpress/dcscb.c - Dual Cluster System Control Block
> + *
> + * Created by:	Nicolas Pitre, May 2012
> + * Copyright:	(C) 2012-2013  Linaro Limited
> + *
> + * 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/init.h>
> +#include <linux/kernel.h>
> +#include <linux/io.h>
> +#include <linux/spinlock.h>
> +#include <linux/errno.h>
> +#include <linux/vexpress.h>
> +
> +#include <asm/mcpm_entry.h>
> +#include <asm/proc-fns.h>
> +#include <asm/cacheflush.h>
> +#include <asm/cputype.h>
> +#include <asm/cp15.h>
> +
> +
> +#define DCSCB_PHYS_BASE	0x60000000
> +
> +#define RST_HOLD0	0x0
> +#define RST_HOLD1	0x4
> +#define SYS_SWRESET	0x8
> +#define RST_STAT0	0xc
> +#define RST_STAT1	0x10
> +#define EAG_CFG_R	0x20
> +#define EAG_CFG_W	0x24
> +#define KFC_CFG_R	0x28
> +#define KFC_CFG_W	0x2c
> +#define DCS_CFG_R	0x30
> +
> +/*
> + * We can't use regular spinlocks. In the switcher case, it is possible
> + * for an outbound CPU to call power_down() after its inbound counterpart
> + * is already live using the same logical CPU number which trips lockdep
> + * debugging.
> + */
> +static arch_spinlock_t dcscb_lock = __ARCH_SPIN_LOCK_UNLOCKED;
> +
> +static void __iomem *dcscb_base;
> +
> +static int dcscb_power_up(unsigned int cpu, unsigned int cluster)
> +{
> +	unsigned int rst_hold, cpumask = (1 << cpu);
> +
> +	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
> +	if (cpu >= 4 || cluster >= 2)

Is this a CCI limitation ?
> +		return -EINVAL;
> +
> +	/*
> +	 * Since this is called with IRQs enabled, and no arch_spin_lock_irq
> +	 * variant exists, we need to disable IRQs manually here.
> +	 */
> +	local_irq_disable();
> +	arch_spin_lock(&dcscb_lock);
> +
> +	rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4);
> +	if (rst_hold & (1 << 8)) {
> +		/* remove cluster reset and add individual CPU's reset */
> +		rst_hold &= ~(1 << 8);
> +		rst_hold |= 0xf;
> +	}
> +	rst_hold &= ~(cpumask | (cpumask << 4));
> +	writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4);
> +
> +	arch_spin_unlock(&dcscb_lock);
> +	local_irq_enable();
> +
> +	return 0;
> +}
> +
> +static void dcscb_power_down(void)
> +{
> +	unsigned int mpidr, cpu, cluster, rst_hold, cpumask, last_man;
> +
> +	mpidr = read_cpuid_mpidr();
> +	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
> +	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
> +	cpumask = (1 << cpu);
> +
> +	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
> +	BUG_ON(cpu >= 4 || cluster >= 2);
> +
> +	arch_spin_lock(&dcscb_lock);
> +	rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4);
> +	rst_hold |= cpumask;
> +	if (((rst_hold | (rst_hold >> 4)) & 0xf) == 0xf)
> +		rst_hold |= (1 << 8);
> +	writel(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4);
> +	arch_spin_unlock(&dcscb_lock);
> +	last_man = (rst_hold & (1 << 8));
> +
> +	/*
> +	 * Now let's clean our L1 cache and shut ourself down.
> +	 * If we're the last CPU in this cluster then clean L2 too.
> +	 */
> +
How about merging these two comments ?
> +	/*
> +	 * A15/A7 can hit in the cache with SCTLR.C=0, so we don't need
> +	 * a preliminary flush here for those CPUs.  At least, that's
> +	 * the theory -- without the extra flush, Linux explodes on
> +	 * RTSM (maybe not needed anymore, to be investigated)..
> +	 */
> +	flush_cache_louis();
> +	cpu_proc_fin();
Lorenzo already noticed the I cache getting disable here.
That should be fixed. Rest of the patch looks fine.

Reviewed-by: Santosh Shilimkar <[email-masked]>