Message-ID: <51E5A785.1040805@gmail.com>
Date:	Tue, 16 Jul 2013 15:05:25 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org,
	Jon Medhurst <tixy@...aro.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pawel Moll <pawel.moll@....com>,
	Achin Gupta <achin.gupta@....com>,
	Amit Kucheria <amit.kucheria@...aro.org>
Subject: Re: [RFC PATCH v5 1/1] drivers: mfd: vexpress: add Serial Power Controller
 (SPC) support

On 07/16/2013 11:05 AM, Lorenzo Pieralisi wrote:
> The TC2 versatile express core tile integrates a logic block that provides the
> interface between the dual cluster test-chip and the M3 microcontroller that
> carries out power management. The logic block, called Serial Power Controller
> (SPC), contains several memory mapped registers to control among other things
> low-power states, wake-up irqs and per-CPU jump addresses registers.
> 
> This patch provides a driver that enables run-time control of features
> implemented by the SPC power management control logic.
> 
> The SPC control logic is required to be programmed very early in the boot
> process to reset secondary CPUs on the TC2 testchip, set-up jump addresses and
> wake-up IRQs for power management. Hence, waiting for core changes to be
> made in the device core code to enable early registration of platform
> devices, the driver puts in place an early init scheme that allows kernel
> drivers to initialize the SPC driver directly from the components requiring
> it, if their initialization routine is called before the driver init
> function by the boot process.
> 
> Device tree bindings documentation for the SPC component is provided with
> the patchset.

Just curious, wouldn't a TC2 PSCI implementation eliminate the need for
most/all of this code?

Rob

> 
> Cc: Samuel Ortiz <sameo@...ux.intel.com>
> Cc: Olof Johansson <olof@...om.net>
> Cc: Pawel Moll <pawel.moll@....com>
> Cc: Amit Kucheria <amit.kucheria@...aro.org>
> Cc: Jon Medhurst <tixy@...aro.org>
> Signed-off-by: Achin Gupta <achin.gupta@....com>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Signed-off-by: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
> ---
>  Documentation/devicetree/bindings/mfd/vexpress-spc.txt |  36 ++
>  drivers/mfd/Kconfig                                    |  10 +
>  drivers/mfd/Makefile                                   |   1 +
>  drivers/mfd/vexpress-spc.c                             | 253 ++++++++++
>  include/linux/vexpress.h                               |  17 +
>  5 files changed, 317 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/vexpress-spc.txt b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
> new file mode 100644
> index 0000000..1614725
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/vexpress-spc.txt
> @@ -0,0 +1,36 @@
> +* ARM Versatile Express Serial Power Controller device tree bindings
> +
> +Latest ARM development boards implement a power management interface (serial
> +power controller - SPC) that is capable of managing power states transitions,
> +wake-up IRQs and resume addresses for ARM multiprocessor testchips.
> +The serial controller can be programmed through a memory mapped interface
> +that enables communication between firmware running on the microcontroller
> +managing power states and the application processors.
> +
> +The SPC DT bindings are defined as follows:
> +
> +- spc node
> +
> +	- compatible:
> +		Usage: required
> +		Value type: <stringlist>
> +		Definition: must be
> +			    "arm,vexpress-spc,v2p-ca15_a7", "arm,vexpress-spc"
> +	- reg:
> +		Usage: required
> +		Value type: <prop-encode-array>
> +		Definition: A standard property that specifies the base address
> +			    and the size of the SPC address space
> +	- interrupts:
> +		Usage: required
> +		Value type: <prop-encoded-array>
> +		Definition:  SPC interrupt configuration. A standard property
> +			     that follows ePAPR interrupts specifications
> +
> +Example:
> +
> +spc: spc@...f0000 {
> +	compatible = "arm,vexpress-spc,v2p-ca15_a7", "arm,vexpress-spc";
> +	reg = <0x7fff0000 0x1000>;
> +	interrupts = <0 95 4>;
> +};
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 6959b8d..ebd23f4 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1149,3 +1149,13 @@ config VEXPRESS_CONFIG
>  	help
>  	  Platform configuration infrastructure for the ARM Ltd.
>  	  Versatile Express.
> +
> +config VEXPRESS_SPC
> +	bool "Versatile Express SPC driver support"
> +	depends on ARM
> +	help
> +	  The Serial Power Controller (SPC) for ARM Ltd. test chips, is
> +	  an IP that provides a memory mapped interface to power controller
> +	  HW. The driver provides an API abstraction allowing to program
> +	  registers controlling low-level power management features like power
> +	  down flags, global and per-cpu wake-up IRQs.
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 718e94a..3a01203 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -153,5 +153,6 @@ obj-$(CONFIG_MFD_SEC_CORE)	+= sec-core.o sec-irq.o
>  obj-$(CONFIG_MFD_SYSCON)	+= syscon.o
>  obj-$(CONFIG_MFD_LM3533)	+= lm3533-core.o lm3533-ctrlbank.o
>  obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o vexpress-sysreg.o
> +obj-$(CONFIG_VEXPRESS_SPC)	+= vexpress-spc.o
>  obj-$(CONFIG_MFD_RETU)		+= retu-mfd.o
>  obj-$(CONFIG_MFD_AS3711)	+= as3711.o
> diff --git a/drivers/mfd/vexpress-spc.c b/drivers/mfd/vexpress-spc.c
> new file mode 100644
> index 0000000..aa8c2a4
> --- /dev/null
> +++ b/drivers/mfd/vexpress-spc.c
> @@ -0,0 +1,253 @@
> +/*
> + * Versatile Express Serial Power Controller (SPC) support
> + *
> + * Copyright (C) 2013 ARM Ltd.
> + *
> + * Authors: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
> + *          Achin Gupta           <achin.gupta@....com>
> + *          Lorenzo Pieralisi     <lorenzo.pieralisi@....com>
> + *
> + * 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.
> + *
> + * 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/device.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +#include <linux/vexpress.h>
> +
> +#include <asm/cacheflush.h>
> +
> +#define SPCLOG "vexpress-spc: "
> +
> +/* SCC conf registers */
> +#define A15_CONF		0x400
> +#define SYS_INFO		0x700
> +
> +/* SPC registers base */
> +#define SPC_BASE		0xB00
> +
> +/* SPC wake-up IRQs status and mask */
> +#define WAKE_INT_MASK		(SPC_BASE + 0x24)
> +#define WAKE_INT_RAW		(SPC_BASE + 0x28)
> +#define WAKE_INT_STAT		(SPC_BASE + 0x2c)
> +/* SPC power down registers */
> +#define A15_PWRDN_EN		(SPC_BASE + 0x30)
> +#define A7_PWRDN_EN		(SPC_BASE + 0x34)
> +/* SPC per-CPU mailboxes */
> +#define A15_BX_ADDR0		(SPC_BASE + 0x68)
> +#define A7_BX_ADDR0		(SPC_BASE + 0x78)
> +
> +/* wake-up interrupt masks */
> +#define GBL_WAKEUP_INT_MSK	(0x3 << 10)
> +
> +/* TC2 static dual-cluster configuration */
> +#define MAX_CLUSTERS		2
> +
> +struct ve_spc_drvdata {
> +	void __iomem *baseaddr;
> +	/*
> +	 * A15s cluster identifier
> +	 * It corresponds to A15 processors MPIDR[15:8] bitfield
> +	 */
> +	u32 a15_clusid;
> +};
> +
> +static struct ve_spc_drvdata *info;
> +
> +static inline bool cluster_is_a15(u32 cluster)
> +{
> +	return cluster == info->a15_clusid;
> +}
> +
> +/**
> + * ve_spc_global_wakeup_irq()
> + *
> + * Function to set/clear global wakeup IRQs. Not protected by locking since
> + * it might be used in code paths where normal cacheable locks are not
> + * working. Locking must be provided by the caller to ensure atomicity.
> + *
> + * @set: if true, global wake-up IRQs are set, if false they are cleared
> + */
> +void ve_spc_global_wakeup_irq(bool set)
> +{
> +	u32 reg;
> +
> +	reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
> +
> +	if (set)
> +		reg |= GBL_WAKEUP_INT_MSK;
> +	else
> +		reg &= ~GBL_WAKEUP_INT_MSK;
> +
> +	writel_relaxed(reg, info->baseaddr + WAKE_INT_MASK);
> +}
> +
> +/**
> + * ve_spc_cpu_wakeup_irq()
> + *
> + * Function to set/clear per-CPU wake-up IRQs. Not protected by locking since
> + * it might be used in code paths where normal cacheable locks are not
> + * working. Locking must be provided by the caller to ensure atomicity.
> + *
> + * @cluster: mpidr[15:8] bitfield describing cluster affinity level
> + * @cpu: mpidr[7:0] bitfield describing cpu affinity level
> + * @set: if true, wake-up IRQs are set, if false they are cleared
> + */
> +void ve_spc_cpu_wakeup_irq(u32 cluster, u32 cpu, bool set)
> +{
> +	u32 mask, reg;
> +
> +	if (cluster >= MAX_CLUSTERS)
> +		return;
> +
> +	mask = 1 << cpu;
> +
> +	if (!cluster_is_a15(cluster))
> +		mask <<= 4;
> +
> +	reg = readl_relaxed(info->baseaddr + WAKE_INT_MASK);
> +
> +	if (set)
> +		reg |= mask;
> +	else
> +		reg &= ~mask;
> +
> +	writel_relaxed(reg, info->baseaddr + WAKE_INT_MASK);
> +}
> +
> +/**
> + * ve_spc_set_resume_addr() - set the jump address used for warm boot
> + *
> + * @cluster: mpidr[15:8] bitfield describing cluster affinity level
> + * @cpu: mpidr[7:0] bitfield describing cpu affinity level
> + * @addr: physical resume address
> + */
> +void ve_spc_set_resume_addr(u32 cluster, u32 cpu, u32 addr)
> +{
> +	void __iomem *baseaddr;
> +
> +	if (cluster >= MAX_CLUSTERS)
> +		return;
> +
> +	if (cluster_is_a15(cluster))
> +		baseaddr = info->baseaddr + A15_BX_ADDR0 + (cpu << 2);
> +	else
> +		baseaddr = info->baseaddr + A7_BX_ADDR0 + (cpu << 2);
> +
> +	writel_relaxed(addr, baseaddr);
> +}
> +
> +/**
> + * ve_spc_get_nr_cpus() - get number of cpus in a cluster
> + *
> + * @cluster: mpidr[15:8] bitfield describing cluster affinity level
> + *
> + * Return: > 0 number of cpus in the cluster
> + *         or 0 if cluster number invalid
> + */
> +u32 ve_spc_get_nr_cpus(u32 cluster)
> +{
> +	u32 val;
> +
> +	if (cluster >= MAX_CLUSTERS)
> +		return 0;
> +
> +	val = readl_relaxed(info->baseaddr + SYS_INFO);
> +	val = cluster_is_a15(cluster) ? (val >> 16) : (val >> 20);
> +	return val & 0xf;
> +}
> +
> +/**
> + * ve_spc_powerdown()
> + *
> + * Function to enable/disable cluster powerdown. Not protected by locking
> + * since it might be used in code paths where normal cacheable locks are not
> + * working. Locking must be provided by the caller to ensure atomicity.
> + *
> + * @cluster: mpidr[15:8] bitfield describing cluster affinity level
> + * @enable: if true enables powerdown, if false disables it
> + */
> +void ve_spc_powerdown(u32 cluster, bool enable)
> +{
> +	u32 pwdrn_reg;
> +
> +	if (cluster >= MAX_CLUSTERS)
> +		return;
> +
> +	pwdrn_reg = cluster_is_a15(cluster) ? A15_PWRDN_EN : A7_PWRDN_EN;
> +	writel_relaxed(enable, info->baseaddr + pwdrn_reg);
> +}
> +
> +static const struct of_device_id ve_spc_ids[] __initconst = {
> +	{ .compatible = "arm,vexpress-spc,v2p-ca15_a7" },
> +	{ .compatible = "arm,vexpress-spc" },
> +	{},
> +};
> +
> +static int __init ve_spc_probe(void)
> +{
> +	int ret;
> +	struct device_node *node = of_find_matching_node(NULL, ve_spc_ids);
> +
> +	if (!node)
> +		return -ENODEV;
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info) {
> +		pr_err(SPCLOG "unable to allocate mem\n");
> +		return -ENOMEM;
> +	}
> +
> +	info->baseaddr = of_iomap(node, 0);
> +	if (!info->baseaddr) {
> +		pr_err(SPCLOG "unable to ioremap memory\n");
> +		ret = -ENXIO;
> +		goto mem_free;
> +	}
> +
> +	info->a15_clusid = readl_relaxed(info->baseaddr + A15_CONF) & 0xf;
> +
> +	/*
> +	 * Multi-cluster systems may need this data when non-coherent, during
> +	 * cluster power-up/power-down. Make sure driver info reaches main
> +	 * memory.
> +	 */
> +	sync_cache_w(info);
> +	sync_cache_w(&info);
> +	pr_info("vexpress-spc loaded at %p\n", info->baseaddr);
> +	return 0;
> +
> +mem_free:
> +	kfree(info);
> +	return ret;
> +}
> +
> +/**
> + * ve_spc_init()
> + *
> + * Function exported to manage pre early_initcall initialization.
> + * SPC code is needed very early in the boot process to bring CPUs out of
> + * reset and initialize power management back-end so an init interface is
> + * provided to platform code to allow early initialization. The init
> + * interface can be removed as soon as the DT layer and platform bus allow
> + * platform device creation and probing before SMP boot.
> + */
> +int __init ve_spc_init(void)
> +{
> +	static int ve_spc_init_status __initdata = -EAGAIN;
> +
> +	if (ve_spc_init_status == -EAGAIN)
> +		ve_spc_init_status = ve_spc_probe();
> +
> +	return ve_spc_init_status;
> +}
> +early_initcall(ve_spc_init);
> diff --git a/include/linux/vexpress.h b/include/linux/vexpress.h
> index 50368e0..d0106ef 100644
> --- a/include/linux/vexpress.h
> +++ b/include/linux/vexpress.h
> @@ -132,4 +132,21 @@ void vexpress_clk_of_register_spc(void);
>  void vexpress_clk_init(void __iomem *sp810_base);
>  void vexpress_clk_of_init(void);
>  
> +/* SPC */
> +
> +#ifdef CONFIG_VEXPRESS_SPC
> +int __init ve_spc_init(void);
> +void ve_spc_global_wakeup_irq(bool set);
> +void ve_spc_cpu_wakeup_irq(u32 cluster, u32 cpu, bool set);
> +void ve_spc_set_resume_addr(u32 cluster, u32 cpu, u32 addr);
> +u32 ve_spc_get_nr_cpus(u32 cluster);
> +void ve_spc_powerdown(u32 cluster, bool enable);
> +#else
> +static inline int ve_spc_init(void) { return -ENODEV; }
> +static inline void ve_spc_global_wakeup_irq(bool set) { }
> +static inline void ve_spc_cpu_wakeup_irq(u32 cluster, u32 cpu, bool set) { }
> +static inline void ve_spc_set_resume_addr(u32 cluster, u32 cpu, u32 addr) { }
> +static inline u32 ve_spc_get_nr_cpus(u32 cluster) { return 0; }
> +static inline void ve_spc_powerdown(u32 cluster, bool enable) { }
> +#endif
>  #endif
> 

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