Message-id: <5260F14F.2060603@samsung.com>
Date: Fri, 18 Oct 2013 12:29:03 +0400
From: Tarek Dakhran <t.dakhran@samsung.com>
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To: Dave Martin <Dave.Martin@arm.com>,
        Vyacheslav Tyrtov <v.tyrtov@samsung.com>
Cc: linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>,
        devicetree@vger.kernel.org, Kukjin Kim <kgene.kim@samsung.com>,
        Russell King <linux@arm.linux.org.uk>, Ben Dooks <ben-linux@fluff.org>,
        Pawel Moll <pawel.moll@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Stephen Warren <swarren@wwwdotorg.org>, linux-doc@vger.kernel.org,
        Rob Herring <rob.herring@calxeda.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        linux-samsung-soc@vger.kernel.org, Rob Landley <rob@landley.net>,
        Mike Turquette <mturquette@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Naour Romain <romain.naour@openwide.fr>,
        linux-arm-kernel@lists.infradead.org, Heiko Stuebner <heiko@sntech.de>
Subject: Re: [PATCH v2 3/4] ARM: EXYNOS: add Exynos Dual Cluster Support
References: <20131017154640.GF2442@localhost.localdomain>
In-reply-to: <20131017154640.GF2442@localhost.localdomain>
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On 17.10.2013 19:46, Dave Martin wrote:
> On Mon, Oct 14, 2013 at 07:08:24PM +0400, Vyacheslav Tyrtov wrote:
>> From: Tarek Dakhran <t.dakhran@samsung.com>
>>
>> Add EDCS(Exynos Dual Cluster Support) for Samsung Exynos5410 SoC.
>> This enables all 8 cores, 4 x A7 and 4 x A15 run at the same time.
>>
>> Signed-off-by: Tarek Dakhran <t.dakhran@samsung.com>
>> Signed-off-by: Vyacheslav Tyrtov <v.tyrtov@samsung.com>
>> ---
>>   arch/arm/mach-exynos/Makefile |   2 +
>>   arch/arm/mach-exynos/edcs.c   | 270 ++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 272 insertions(+)
>>   create mode 100644 arch/arm/mach-exynos/edcs.c
>>
>> diff --git a/arch/arm/mach-exynos/Makefile b/arch/arm/mach-exynos/Makefile
>> index 5369615..ba6efdb 100644
>> --- a/arch/arm/mach-exynos/Makefile
>> +++ b/arch/arm/mach-exynos/Makefile
>> @@ -34,3 +34,5 @@ AFLAGS_exynos-smc.o		:=-Wa,-march=armv7-a$(plus_sec)
>>   
>>   obj-$(CONFIG_MACH_EXYNOS4_DT)		+= mach-exynos4-dt.o
>>   obj-$(CONFIG_MACH_EXYNOS5_DT)		+= mach-exynos5-dt.o
>> +
>> +obj-$(CONFIG_SOC_EXYNOS5410)		+= edcs.o
>> diff --git a/arch/arm/mach-exynos/edcs.c b/arch/arm/mach-exynos/edcs.c
>> new file mode 100644
>> index 0000000..e304bd9
>> --- /dev/null
>> +++ b/arch/arm/mach-exynos/edcs.c
>> @@ -0,0 +1,270 @@
>> +/*
>> + * arch/arm/mach-exynos/edcs.c - exynos dual cluster power management support
>> + *
>> + * Copyright (c) 2013 Samsung Electronics Co., Ltd.
>> + * Author: Tarek Dakhran <t.dakhran@samsung.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.
>> + *
>> + * EDCS(exynos dual cluster support) for Exynos5410 SoC.
>> + */
>> +
[snip]
>> +#define EDCS_CORE_STATUS(_nr)		(EDCS_CORE_CONFIGURATION(_nr) + 0x4)
>> +#define EDCS_CORE_OPTION(_nr)		(EDCS_CORE_CONFIGURATION(_nr) + 0x8)
>> +
>> +#define REG_CPU_STATE_ADDR0		(S5P_VA_SYSRAM_NS + 0x28)
> Is there any reason why S5P_VA_SYSRAM_NS needs to be a static mapping?
What do you mean by "static mapping"?
>
>> +#define REG_CPU_STATE_ADDR(_nr)		(REG_CPU_STATE_ADDR0 +	\
>> +						 _nr * EDCS_CPUS_PER_CLUSTER)
>> +
>> +static arch_spinlock_t edcs_lock = __ARCH_SPIN_LOCK_UNLOCKED;
>> +
>> +static int edcs_use_count[EDCS_CPUS_PER_CLUSTER][EDCS_CLUSTERS];
>> +static int core_count[EDCS_CLUSTERS];
>> +
>> +static void exynos_core_power_control(unsigned int cpu, unsigned int cluster,
>> +				bool enable)
>> +{
>> +	unsigned int offset = cluster * EDCS_CPUS_PER_CLUSTER + cpu;
>> +	int value = enable ? S5P_CORE_LOCAL_PWR_EN : 0;
>> +
>> +	if ((__raw_readl(EDCS_CORE_STATUS(offset)) & 0x3) != value)
>> +		__raw_writel(value, EDCS_CORE_CONFIGURATION(offset));
> I think you need to replace all the __raw_readl() / __raw_writel() calls
> in this file with readl_relaxed() / writel_relaxed().
>
> This ensures little-endian byte order, so that BE8 kernels will work.
>
Will be done.
>> +}
>> +
>> +static void exynos_core_power_up(unsigned int cpu, unsigned int cluster)
>> +{
>> +	exynos_core_power_control(cpu, cluster, true);
>> +}
[snip]
>> +
>> +	edcs_use_count[cpu][cluster]++;
>> +	if (edcs_use_count[cpu][cluster] == 1) {
>> +		++core_count[cluster];
>> +		set_boot_flag(cpu, 0x2);
> 0x2 looks like a magic number.  Can we have a #define for that?
Will be done.
> If the boot flag is read by the inbound CPU or by a peripheral then
> there are memory ordering issues to take into account.  Otherwise, can't
> the inbound CPU come online and race with the write to the boot flag?
Inbound CPU doesn't write the boot flag.
> What is the memory type of REG_STATE_ADDR()?
Same type as S5P_VA_SYSRAM_NS.
This 4K region is mapped as follows:

static struct map_desc exynos5410_iodesc[] __initdata = {
	{
		.virtual	= (unsigned long)S5P_VA_SYSRAM_NS,
		.pfn		= __phys_to_pfn(EXYNOS5410_PA_SYSRAM_NS),
		.length		= SZ_4K,
		.type		= MT_DEVICE,
	},
};


>> +		exynos_core_power_up(cpu, cluster);
>> +	} else if (edcs_use_count[cpu][cluster] != 2) {
>> +		/*
>> +		 * The only possible values are:
>> +		 * 0 = CPU down
>> +		 * 1 = CPU (still) up
>> +		 * 2 = CPU requested to be up before it had a chance
>> +		 *     to actually make itself down.
>> +		 * Any other value is a bug.
>> +		 */
>> +		BUG();
>> +	}
>> +
>> +	arch_spin_unlock(&edcs_lock);
>> +	local_irq_enable();
>> +
>> +	return 0;
>> +}
>> +static void exynos_power_down(void)
>> +{
>> +	unsigned int mpidr, cpu, cluster;
>> +	bool last_man = false, skip_wfi = false;
>> +
>> +	mpidr = read_cpuid_mpidr();
>> +	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
>> +	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
>> +
>> +	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
>> +	BUG_ON(cpu >= EDCS_CPUS_PER_CLUSTER  || cluster >= EDCS_CLUSTERS);
>> +
>> +	__mcpm_cpu_going_down(cpu, cluster);
>> +
>> +	arch_spin_lock(&edcs_lock);
>> +	BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
>> +	edcs_use_count[cpu][cluster]--;
>> +	if (edcs_use_count[cpu][cluster] == 0) {
>> +		--core_count[cluster];
>> +		if (core_count[cluster] == 0)
>> +			last_man = true;
>> +	} else if (edcs_use_count[cpu][cluster] == 1) {
>> +		/*
>> +		 * A power_up request went ahead of us.
>> +		 * Even if we do not want to shut this CPU down,
>> +		 * the caller expects a certain state as if the WFI
>> +		 * was aborted.  So let's continue with cache cleaning.
>> +		 */
>> +		skip_wfi = true;
>> +	} else
>> +		BUG();
> For TC2, Lorenzo discovered need to disable the GIC CPU interface, so
> that no suprious wakeups can happen once the power controller is
> configured to power the CPU down.
>
> The problem is that a spurious wakeup can trigger a race in the power
> controller when the last man powers down, where the power controller
> continues to wait for the cluster to power down, but it never happens.
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-September/200917.html
> ([PATCH v2] arm: vexpress: tc2: fix hotplug/idle/kexec race on cluster power down)
>
>
> This might not be a problem for Exynos5410 -- it depends on the way the
> power control logic works.
>
> On the other hand, disabling the GIC CPU interface here is cheap to do,
> even if it's not really needed.
>
>> +
>> +	if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
>> +		arch_spin_unlock(&edcs_lock);
>> +
>> +		if (read_cpuid_part_number() == ARM_CPU_PART_CORTEX_A15) {
>> +			/*
>> +			 * On the Cortex-A15 we need to disable
>> +			 * L2 prefetching before flushing the cache.
>> +			 */
>> +			asm volatile(
>> +			"mcr	p15, 1, %0, c15, c0, 3\n\t"
>> +			"isb\n\t"
>> +			"dsb"
>> +			: : "r" (0x400));
>> +		}
>> +
>> +		/*
>> +		 * We need to disable and flush the whole (L1 and L2) cache.
>> +		 * Let's do it in the safest possible way i.e. with
>> +		 * no memory access within the following sequence
>> +		 * including the stack.
>> +		 *
>> +		 * Note: fp is preserved to the stack explicitly prior doing
>> +		 * this since adding it to the clobber list is incompatible
>> +		 * with having CONFIG_FRAME_POINTER=y.
>> +		 */
>> +		asm volatile(
>> +		"str	fp, [sp, #-4]!\n\t"
>> +		"mrc	p15, 0, r0, c1, c0, 0	@ get CR\n\t"
>> +		"bic	r0, r0, #"__stringify(CR_C)"\n\t"
>> +		"mcr	p15, 0, r0, c1, c0, 0	@ set CR\n\t"
>> +		"isb\n\t"
>> +		"bl	v7_flush_dcache_all\n\t"
>> +		"clrex\n\t"
>> +		"mrc	p15, 0, r0, c1, c0, 1	@ get AUXCR\n\t"
>> +		"bic	r0, r0, #(1 << 6)	@ disable local coherency\n\t"
>> +		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR\n\t"
>> +		"isb\n\t"
>> +		"dsb\n\t"
>> +		"ldr	fp, [sp], #4"
>> +		: : : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
>> +			"r9", "r10", "lr", "memory");
> For these code sequences, please take a look at
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-October/205085.html
> [PATCH] ARM: cacheflush: consolidate single-CPU ARMv7 cache disabling code
>
> The aim is to consolidate on a macro that can be shared between
> backends.
Will be done right after Nicolases patch will be applied to the mainline.
>
>> +
>> +		cci_disable_port_by_cpu(mpidr);
>> +
>> +		__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
>> +
>> +	} else {
>> +		arch_spin_unlock(&edcs_lock);
>> +		/*
>> +			* We need to disable and flush only the L1 cache.
>> +			* Let's do it in the safest possible way as above.
>> +		*/
>> +		asm volatile(
>> +		"str	fp, [sp, #-4]!\n\t"
>> +		"mrc	p15, 0, r0, c1, c0, 0	@ get CR\n\t"
>> +		"bic	r0, r0, #"__stringify(CR_C)"\n\t"
>> +		"mcr	p15, 0, r0, c1, c0, 0	@ set CR\n\t"
>> +		"isb\n\t"
>> +		"bl	v7_flush_dcache_louis\n\t"
>> +		"clrex\n\t"
>> +		"mrc	p15, 0, r0, c1, c0, 1	@ get AUXCR\n\t"
>> +		"bic	r0, r0, #(1 << 6)	@ disable local coherency\n\t"
>> +		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR\n\t"
>> +		"isb\n\t"
>> +		"dsb\n\t"
>> +		"ldr	fp, [sp], #4"
>> +		: : : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
>> +		      "r9", "r10", "lr", "memory");
>> +
>> +	}
>> +	__mcpm_cpu_down(cpu, cluster);
>> +
>> +	if (!skip_wfi) {
>> +		exynos_core_power_down(cpu, cluster);
>> +		wfi();
>> +	}
>> +}
>> +
>> +static const struct mcpm_platform_ops exynos_power_ops = {
>> +	.power_up	= exynos_power_up,
>> +	.power_down	= exynos_power_down,
>> +};
>> +
>> +static void __init edcs_data_init(void)
>> +{
>> +	unsigned int mpidr, cpu, cluster;
>> +
>> +	mpidr = read_cpuid_mpidr();
>> +	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
>> +	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
>> +
>> +	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
>> +	BUG_ON(cpu >= EDCS_CPUS_PER_CLUSTER  || cluster >= EDCS_CLUSTERS);
>> +	edcs_use_count[cpu][cluster] = 1;
>> +	++core_count[cluster];
>> +}
>> +
>> +/*
>> + * Enable cluster-level coherency, in preparation for turning on the MMU.
>> + */
>> +static void __naked edcs_power_up_setup(unsigned int affinity_level)
>> +{
>> +	asm volatile ("\n"
>> +	"b	cci_enable_port_for_self");
>> +}
>> +
>> +static int __init edcs_init(void)
>> +{
>> +	int ret;
>> +	struct device_node *node;
>> +
>> +	node = of_find_compatible_node(NULL, NULL, "samsung,exynos5410");
>> +	if (!node)
>> +		return -ENODEV;
>> +
>> +	if (!cci_probed())
>> +		return -ENODEV;
>> +
>> +	/*
>> +	 * Future entries into the kernel can now go
>> +	 * through the cluster entry vectors.
>> +	 */
>> +	__raw_writel(virt_to_phys(mcpm_entry_point),
>> +				S5P_VA_SYSRAM_NS + 0x1c);
> It would me more readable to have a #define to describe what
> S5P_VA_SYSRAM_NS + 0x1c is.
Will be done.
> Also, what is the memory type of S5P_VA_SYSRAM_NS?  How is the entry
> point address value read?  Does the inbound CPU's boot ROM or firmware
> read it?
The former (i.e. boot ROM reads it).
> If it is read via some non-coherent side-channel, or if S5P_VA_SYSRAM_NS
> is mapped as normal memory then we would need some explicit
> synchronisation, but I suspect this is not the case (?)
>
> Cheers
> ---Dave
>
>> +
>> +	edcs_data_init();
>> +	mcpm_smp_set_ops();
>> +
>> +	ret = mcpm_platform_register(&exynos_power_ops);
>> +	if (!ret) {
>> +		mcpm_sync_init(edcs_power_up_setup);
>> +		pr_info("EDCS power management initialized\n");
>> +	}
>> +	return ret;
>> +}
>> +
>> +early_initcall(edcs_init);
>> -- 
>> 1.8.1.5
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Thanks for your comments.

Sincerely yours,
     Tarek Dakhran
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