Re: [PATCH v2 3/4] ARM: EXYNOS: add Exynos Dual Cluster Support

[Tarek Dakhran]

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@xxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxx>
> > Signed-off-by: Vyacheslav Tyrtov <v.tyrtov@xxxxxxxxxxx>
> > ---
> >   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@xxxxxxxxxxx>
> > + *
> > + * 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@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Thanks for your comments.

Sincerely yours,
    Tarek Dakhran
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/