arch/arc/kernel/mcip.c

/*
 * ARC ARConnect (MultiCore IP) support (formerly known as MCIP)
 *
 * Copyright (C) 2013 Synopsys, Inc. (www.synopsys.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.
 */

#include <linux/smp.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <asm/irqflags-arcv2.h>
#include <asm/mcip.h>
#include <asm/setup.h>

#define SOFTIRQ_IRQ	21

static char smp_cpuinfo_buf[128];
static int idu_detected;

static DEFINE_RAW_SPINLOCK(mcip_lock);

static void mcip_setup_per_cpu(int cpu)
{
	smp_ipi_irq_setup(cpu, IPI_IRQ);
	smp_ipi_irq_setup(cpu, SOFTIRQ_IRQ);
}

static void mcip_ipi_send(int cpu)
{
	unsigned long flags;
	int ipi_was_pending;

	/* ARConnect can only send IPI to others */
	if (unlikely(cpu == raw_smp_processor_id())) {
		arc_softirq_trigger(SOFTIRQ_IRQ);
		return;
	}

	/*
	 * NOTE: We must spin here if the other cpu hasn't yet
	 * serviced a previous message. This can burn lots
	 * of time, but we MUST follows this protocol or
	 * ipi messages can be lost!!!
	 * Also, we must release the lock in this loop because
	 * the other side may get to this same loop and not
	 * be able to ack -- thus causing deadlock.
	 */

	do {
		raw_spin_lock_irqsave(&mcip_lock, flags);
		__mcip_cmd(CMD_INTRPT_READ_STATUS, cpu);
		ipi_was_pending = read_aux_reg(ARC_REG_MCIP_READBACK);
		if (ipi_was_pending == 0)
			break; /* break out but keep lock */
		raw_spin_unlock_irqrestore(&mcip_lock, flags);
	} while (1);

	__mcip_cmd(CMD_INTRPT_GENERATE_IRQ, cpu);
	raw_spin_unlock_irqrestore(&mcip_lock, flags);

#ifdef CONFIG_ARC_IPI_DBG
	if (ipi_was_pending)
		pr_info("IPI ACK delayed from cpu %d\n", cpu);
#endif
}

static void mcip_ipi_clear(int irq)
{
	unsigned int cpu, c;
	unsigned long flags;
	unsigned int __maybe_unused copy;

	if (unlikely(irq == SOFTIRQ_IRQ)) {
		arc_softirq_clear(irq);
		return;
	}

	raw_spin_lock_irqsave(&mcip_lock, flags);

	/* Who sent the IPI */
	__mcip_cmd(CMD_INTRPT_CHECK_SOURCE, 0);

	copy = cpu = read_aux_reg(ARC_REG_MCIP_READBACK);	/* 1,2,4,8... */

	/*
	 * In rare case, multiple concurrent IPIs sent to same target can
	 * possibly be coalesced by MCIP into 1 asserted IRQ, so @cpus can be
	 * "vectored" (multiple bits sets) as opposed to typical single bit
	 */
	do {
		c = __ffs(cpu);			/* 0,1,2,3 */
		__mcip_cmd(CMD_INTRPT_GENERATE_ACK, c);
		cpu &= ~(1U << c);
	} while (cpu);

	raw_spin_unlock_irqrestore(&mcip_lock, flags);

#ifdef CONFIG_ARC_IPI_DBG
	if (c != __ffs(copy))
		pr_info("IPIs from %x coalesced to %x\n",
			copy, raw_smp_processor_id());
#endif
}

static void mcip_probe_n_setup(void)
{
	struct mcip_bcr {
#ifdef CONFIG_CPU_BIG_ENDIAN
		unsigned int pad3:8,
			     idu:1, llm:1, num_cores:6,
			     iocoh:1,  grtc:1, dbg:1, pad2:1,
			     msg:1, sem:1, ipi:1, pad:1,
			     ver:8;
#else
		unsigned int ver:8,
			     pad:1, ipi:1, sem:1, msg:1,
			     pad2:1, dbg:1, grtc:1, iocoh:1,
			     num_cores:6, llm:1, idu:1,
			     pad3:8;
#endif
	} mp;

	READ_BCR(ARC_REG_MCIP_BCR, mp);

	sprintf(smp_cpuinfo_buf,
		"Extn [SMP]\t: ARConnect (v%d): %d cores with %s%s%s%s\n",
		mp.ver, mp.num_cores,
		IS_AVAIL1(mp.ipi, "IPI "),
		IS_AVAIL1(mp.idu, "IDU "),
		IS_AVAIL1(mp.dbg, "DEBUG "),
		IS_AVAIL1(mp.grtc, "GRTC"));

	idu_detected = mp.idu;

	if (mp.dbg) {
		__mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
		__mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
	}

	if (IS_ENABLED(CONFIG_ARC_HAS_GRTC) && !mp.grtc)
		panic("kernel trying to use non-existent GRTC\n");
}

struct plat_smp_ops plat_smp_ops = {
	.info		= smp_cpuinfo_buf,
	.init_early_smp	= mcip_probe_n_setup,
	.init_per_cpu	= mcip_setup_per_cpu,
	.ipi_send	= mcip_ipi_send,
	.ipi_clear	= mcip_ipi_clear,
};

/***************************************************************************
 * ARCv2 Interrupt Distribution Unit (IDU)
 *
 * Connects external "COMMON" IRQs to core intc, providing:
 *  -dynamic routing (IRQ affinity)
 *  -load balancing (Round Robin interrupt distribution)
 *  -1:N distribution
 *
 * It physically resides in the MCIP hw block
 */

#include <linux/irqchip.h>
#include <linux/of.h>
#include <linux/of_irq.h>

/*
 * Set the DEST for @cmn_irq to @cpu_mask (1 bit per core)
 */
static void idu_set_dest(unsigned int cmn_irq, unsigned int cpu_mask)
{
	__mcip_cmd_data(CMD_IDU_SET_DEST, cmn_irq, cpu_mask);
}

static void idu_set_mode(unsigned int cmn_irq, unsigned int lvl,
			   unsigned int distr)
{
	union {
		unsigned int word;
		struct {
			unsigned int distr:2, pad:2, lvl:1, pad2:27;
		};
	} data;

	data.distr = distr;
	data.lvl = lvl;
	__mcip_cmd_data(CMD_IDU_SET_MODE, cmn_irq, data.word);
}

static void idu_irq_mask(struct irq_data *data)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&mcip_lock, flags);
	__mcip_cmd_data(CMD_IDU_SET_MASK, data->hwirq, 1);
	raw_spin_unlock_irqrestore(&mcip_lock, flags);
}

static void idu_irq_unmask(struct irq_data *data)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&mcip_lock, flags);
	__mcip_cmd_data(CMD_IDU_SET_MASK, data->hwirq, 0);
	raw_spin_unlock_irqrestore(&mcip_lock, flags);
}

#ifdef CONFIG_SMP
static int
idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
		     bool force)
{
	unsigned long flags;
	cpumask_t online;

	/* errout if no online cpu per @cpumask */
	if (!cpumask_and(&online, cpumask, cpu_online_mask))
		return -EINVAL;

	raw_spin_lock_irqsave(&mcip_lock, flags);

	idu_set_dest(data->hwirq, cpumask_bits(&online)[0]);
	idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);

	raw_spin_unlock_irqrestore(&mcip_lock, flags);

	return IRQ_SET_MASK_OK;
}
#endif

static struct irq_chip idu_irq_chip = {
	.name			= "MCIP IDU Intc",
	.irq_mask		= idu_irq_mask,
	.irq_unmask		= idu_irq_unmask,
#ifdef CONFIG_SMP
	.irq_set_affinity       = idu_irq_set_affinity,
#endif

};

static int idu_first_irq;

static void idu_cascade_isr(struct irq_desc *desc)
{
	struct irq_domain *domain = irq_desc_get_handler_data(desc);
	unsigned int core_irq = irq_desc_get_irq(desc);
	unsigned int idu_irq;

	idu_irq = core_irq - idu_first_irq;
	generic_handle_irq(irq_find_mapping(domain, idu_irq));
}

static int idu_irq_map(struct irq_domain *d, unsigned int virq, irq_hw_number_t hwirq)
{
	irq_set_chip_and_handler(virq, &idu_irq_chip, handle_level_irq);
	irq_set_status_flags(virq, IRQ_MOVE_PCNTXT);

	return 0;
}

static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
			 const u32 *intspec, unsigned int intsize,
			 irq_hw_number_t *out_hwirq, unsigned int *out_type)
{
	irq_hw_number_t hwirq = *out_hwirq = intspec[0];
	int distri = intspec[1];
	unsigned long flags;

	*out_type = IRQ_TYPE_NONE;

	/* XXX: validate distribution scheme again online cpu mask */
	if (distri == 0) {
		/* 0 - Round Robin to all cpus, otherwise 1 bit per core */
		raw_spin_lock_irqsave(&mcip_lock, flags);
		idu_set_dest(hwirq, BIT(num_online_cpus()) - 1);
		idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
		raw_spin_unlock_irqrestore(&mcip_lock, flags);
	} else {
		/*
		 * DEST based distribution for Level Triggered intr can only
		 * have 1 CPU, so generalize it to always contain 1 cpu
		 */
		int cpu = ffs(distri);

		if (cpu != fls(distri))
			pr_warn("IDU irq %lx distri mode set to cpu %x\n",
				hwirq, cpu);

		raw_spin_lock_irqsave(&mcip_lock, flags);
		idu_set_dest(hwirq, cpu);
		idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_DEST);
		raw_spin_unlock_irqrestore(&mcip_lock, flags);
	}

	return 0;
}

static const struct irq_domain_ops idu_irq_ops = {
	.xlate	= idu_irq_xlate,
	.map	= idu_irq_map,
};

/*
 * [16, 23]: Statically assigned always private-per-core (Timers, WDT, IPI)
 * [24, 23+C]: If C > 0 then "C" common IRQs
 * [24+C, N]: Not statically assigned, private-per-core
 */


static int __init
idu_of_init(struct device_node *intc, struct device_node *parent)
{
	struct irq_domain *domain;
	/* Read IDU BCR to confirm nr_irqs */
	int nr_irqs = of_irq_count(intc);
	int i, irq;

	if (!idu_detected)
		panic("IDU not detected, but DeviceTree using it");

	pr_info("MCIP: IDU referenced from Devicetree %d irqs\n", nr_irqs);

	domain = irq_domain_add_linear(intc, nr_irqs, &idu_irq_ops, NULL);

	/* Parent interrupts (core-intc) are already mapped */

	for (i = 0; i < nr_irqs; i++) {
		/*
		 * Return parent uplink IRQs (towards core intc) 24,25,.....
		 * this step has been done before already
		 * however we need it to get the parent virq and set IDU handler
		 * as first level isr
		 */
		irq = irq_of_parse_and_map(intc, i);
		if (!i)
			idu_first_irq = irq;

		irq_set_chained_handler_and_data(irq, idu_cascade_isr, domain);
	}

	__mcip_cmd(CMD_IDU_ENABLE, 0);

	return 0;
}
IRQCHIP_DECLARE(arcv2_idu_intc, "snps,archs-idu-intc", idu_of_init);