Date:   Thu, 30 Sep 2021 17:21:37 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Huacai Chen <chenhuacai@...ngson.cn>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Huacai Chen <chenhuacai@...il.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: Re: [PATCH V5 09/10] irqchip: Add Loongson Extended I/O interrupt controller support

On Thu, 16 Sep 2021 13:31:37 +0100,
Huacai Chen <chenhuacai@...ngson.cn> wrote:
> 
> We are preparing to add new Loongson (based on LoongArch, not compatible
> with old MIPS-based Loongson) support. This patch add Loongson Extended
> I/O CPU interrupt controller support.
> 
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
>  drivers/irqchip/Kconfig                |  10 +
>  drivers/irqchip/Makefile               |   1 +
>  drivers/irqchip/irq-loongson-eiointc.c | 373 +++++++++++++++++++++++++
>  include/linux/cpuhotplug.h             |   1 +
>  4 files changed, 385 insertions(+)
>  create mode 100644 drivers/irqchip/irq-loongson-eiointc.c
> 
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index 443c3a7a0cc1..aff08ad824c9 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -547,6 +547,16 @@ config LOONGSON_LIOINTC
>  	help
>  	  Support for the Loongson Local I/O Interrupt Controller.
>  
> +config LOONGSON_EIOINTC
> +	bool "Loongson Extend I/O Interrupt Controller"
> +	depends on LOONGARCH
> +	depends on MACH_LOONGSON64
> +	default MACH_LOONGSON64
> +	select IRQ_DOMAIN_HIERARCHY
> +	select GENERIC_IRQ_CHIP
> +	help
> +	  Support for the Loongson3 Extend I/O Interrupt Vector Controller.
> +
>  config LOONGSON_HTPIC
>  	bool "Loongson3 HyperTransport PIC Controller"
>  	depends on (MACH_LOONGSON64 && MIPS)
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index 4e34eebe180b..eb3fdc6fe808 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -107,6 +107,7 @@ obj-$(CONFIG_TI_SCI_INTA_IRQCHIP)	+= irq-ti-sci-inta.o
>  obj-$(CONFIG_TI_PRUSS_INTC)		+= irq-pruss-intc.o
>  obj-$(CONFIG_IRQ_LOONGARCH_CPU)		+= irq-loongarch-cpu.o
>  obj-$(CONFIG_LOONGSON_LIOINTC)		+= irq-loongson-liointc.o
> +obj-$(CONFIG_LOONGSON_EIOINTC)		+= irq-loongson-eiointc.o
>  obj-$(CONFIG_LOONGSON_HTPIC)		+= irq-loongson-htpic.o
>  obj-$(CONFIG_LOONGSON_HTVEC)		+= irq-loongson-htvec.o
>  obj-$(CONFIG_LOONGSON_PCH_PIC)		+= irq-loongson-pch-pic.o
> diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
> new file mode 100644
> index 000000000000..353c91ea5ad2
> --- /dev/null
> +++ b/drivers/irqchip/irq-loongson-eiointc.c
> @@ -0,0 +1,373 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Loongson Extend I/O Interrupt Controller support
> + *
> + * Copyright (C) 2020-2021 Loongson Technology Corporation Limited
> + */
> +
> +#define pr_fmt(fmt) "eiointc: " fmt
> +
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqdomain.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_platform.h>
> +#include <linux/syscore_ops.h>
> +
> +#define EIOINTC_REG_NODEMAP	0x14a0
> +#define EIOINTC_REG_IPMAP	0x14c0
> +#define EIOINTC_REG_ENABLE	0x1600
> +#define EIOINTC_REG_BOUNCE	0x1680
> +#define EIOINTC_REG_ISR		0x1800
> +#define EIOINTC_REG_ROUTE	0x1c00
> +
> +#define VEC_REG_COUNT		4
> +#define VEC_COUNT_PER_REG	64
> +#define VEC_COUNT		(VEC_REG_COUNT * VEC_COUNT_PER_REG)
> +#define VEC_REG_IDX(irq_id)	((irq_id) / VEC_COUNT_PER_REG)
> +#define VEC_REG_BIT(irq_id)     ((irq_id) % VEC_COUNT_PER_REG)
> +#define EIOINTC_DEF_ENABLE	0xffffffff
> +
> +static int nr_pics;
> +
> +struct eiointc_priv {
> +	u32			node;
> +	nodemask_t		node_map;
> +	cpumask_t		cpuspan_map;
> +	struct fwnode_handle	*domain_handle;
> +	struct irq_domain	*eiointc_domain;
> +};
> +
> +struct eiointc_priv *eiointc_priv[2];
> +
> +int eiointc_get_node(int id)
> +{
> +	return eiointc_priv[id]->node;
> +}

Why aren't these static?

> +
> +static void eiointc_set_irq_route(int pos, unsigned int cpu, unsigned int mnode, nodemask_t *node_map)
> +{
> +	int node, cpu_node, route_node;
> +	unsigned char coremap[MAX_NUMNODES];
> +	uint32_t pos_off, data, data_byte, data_mask;
> +
> +	pos_off = pos & ~3;
> +	data_byte = pos & 3;
> +	data_mask = ~BIT_MASK(data_byte) & 0xf;
> +
> +	memset(coremap, 0, sizeof(unsigned char) * MAX_NUMNODES);
> +
> +	/* Calculate node and coremap of target irq */
> +	cpu_node = cpu_to_node(cpu);
> +	coremap[cpu_node] |= (1 << (topology_core_id(cpu)));

BIT()?

> +
> +	for_each_online_node(node) {
> +		if (!node_isset(node, *node_map))
> +			continue;
> +
> +		/* Node 0 is in charge of inter-node interrupt dispatch */
> +		route_node = (node == mnode) ? cpu_node : node;
> +		data = ((coremap[node] | (route_node << 4)) << (data_byte * 8));
> +		csr_any_send(EIOINTC_REG_ROUTE + pos_off, data, data_mask, node);
> +	}
> +}
> +
> +static DEFINE_SPINLOCK(affinity_lock);
> +
> +static int eiointc_set_irq_affinity(struct irq_data *d, const struct cpumask *affinity, bool force)
> +{
> +	unsigned int cpu;
> +	unsigned long flags;
> +	uint32_t vector, pos_off;
> +	struct cpumask intersect_affinity;
> +	struct eiointc_priv *priv = (struct eiointc_priv *)d->domain->host_data;

Drop the cast.

> +
> +	if (!IS_ENABLED(CONFIG_SMP))
> +		return -EPERM;
> +
> +	spin_lock_irqsave(&affinity_lock, flags);

This must be a raw spinlock.

> +
> +	cpumask_and(&intersect_affinity, affinity, cpu_online_mask);
> +	cpumask_and(&intersect_affinity, &intersect_affinity, &priv->cpuspan_map);
> +
> +	if (cpumask_empty(&intersect_affinity)) {
> +		spin_unlock_irqrestore(&affinity_lock, flags);
> +		return -EINVAL;
> +	}
> +	cpu = cpumask_first(&intersect_affinity);
> +
> +	/*
> +	 * Control interrupt enable or disalbe through cpu 0
> +	 * which is reponsible for dispatching interrupts.
> +	 */
> +	if (!d->parent_data)
> +		vector = d->hwirq;
> +	else
> +		vector = d->parent_data->hwirq;
> +
> +	pos_off = vector >> 5;
> +
> +	csr_any_send(EIOINTC_REG_ENABLE + (pos_off << 2),
> +		     EIOINTC_DEF_ENABLE & (~((1 << (vector & 0x1F)))), 0x0, 0);
> +	eiointc_set_irq_route(vector, cpu, priv->node, &priv->node_map);
> +	csr_any_send(EIOINTC_REG_ENABLE + (pos_off << 2), EIOINTC_DEF_ENABLE, 0x0, 0);

These bit shifts are undecipherable. At the very least, explain what
this is doing.

> +
> +	irq_data_update_effective_affinity(d, cpumask_of(cpu));
> +
> +	spin_unlock_irqrestore(&affinity_lock, flags);
> +
> +	return IRQ_SET_MASK_OK;
> +}
> +
> +static int eiointc_index(int node)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_pics; i++) {
> +		if (node_isset(node, eiointc_priv[i]->node_map))
> +			return i;
> +	}
> +
> +	return -1;
> +}
> +
> +static int eiointc_router_init(unsigned int cpu)
> +{
> +	int i, bit;
> +	uint32_t data;
> +	uint32_t node = cpu_to_node(cpu);
> +	uint32_t index = eiointc_index(node);
> +
> +	if (index < 0) {
> +		pr_err("Error: invalid nodemap!\n");
> +		return -1;
> +	}
> +
> +	if (cpu == cpumask_first(cpumask_of_node(node))) {
> +		eiointc_enable();
> +
> +		for (i = 0; i < VEC_COUNT / 32; i++) {
> +			data = (((1 << (i * 2 + 1)) << 16) | (1 << (i * 2)));
> +			iocsr_writel(data, EIOINTC_REG_NODEMAP + i * 4);
> +		}
> +
> +		for (i = 0; i < VEC_COUNT / 32 / 4; i++) {
> +			bit = BIT(1 + index); /* Route to IP[1 + index] */
> +			data = bit | (bit << 8) | (bit << 16) | (bit << 24);
> +			iocsr_writel(data, EIOINTC_REG_IPMAP + i * 4);
> +		}
> +
> +		for (i = 0; i < VEC_COUNT / 4; i++) {
> +			/* Route to Node-0 Core-0 */
> +			if (index == 0)
> +				bit = BIT(cpu_logical_map(0));
> +			else
> +				bit = (eiointc_priv[index]->node << 4) | 1;
> +
> +			data = bit | (bit << 8) | (bit << 16) | (bit << 24);
> +			iocsr_writel(data, EIOINTC_REG_ROUTE + i * 4);
> +		}
> +
> +		for (i = 0; i < VEC_COUNT / 32; i++) {
> +			data = 0xffffffff;
> +			iocsr_writel(data, EIOINTC_REG_ENABLE + i * 4);
> +			iocsr_writel(data, EIOINTC_REG_BOUNCE + i * 4);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void eiointc_irq_dispatch(struct irq_desc *desc)
> +{
> +	int i;
> +	u64 pending;
> +	bool handled = false;
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	struct eiointc_priv *priv = irq_desc_get_handler_data(desc);
> +
> +	chained_irq_enter(chip, desc);
> +
> +	for (i = 0; i < VEC_REG_COUNT; i++) {
> +		pending = iocsr_readq(EIOINTC_REG_ISR + (i << 3));
> +		iocsr_writeq(pending, EIOINTC_REG_ISR + (i << 3));
> +		while (pending) {
> +			int bit = __ffs(pending);
> +			int irq = bit + VEC_COUNT_PER_REG * i;
> +
> +			generic_handle_domain_irq(priv->eiointc_domain, irq);
> +			pending &= ~BIT(bit);
> +			handled = true;
> +		}
> +	}
> +
> +	if (!handled)
> +		spurious_interrupt();
> +
> +	chained_irq_exit(chip, desc);
> +}
> +
> +static void eiointc_ack_irq(struct irq_data *d)
> +{
> +}
> +
> +static void eiointc_mask_irq(struct irq_data *d)
> +{
> +}
> +
> +static void eiointc_unmask_irq(struct irq_data *d)
> +{
> +}
> +
> +static struct irq_chip eiointc_irq_chip = {
> +	.name			= "EIOINTC",
> +	.irq_ack		= eiointc_ack_irq,
> +	.irq_mask		= eiointc_mask_irq,
> +	.irq_unmask		= eiointc_unmask_irq,
> +	.irq_set_affinity	= eiointc_set_irq_affinity,

If this is only routing interrupts, why isn't this a hierarchical
interrupt controller that passes all the callbacks directly to the
parent?

> +};
> +
> +static int eiointc_domain_alloc(struct irq_domain *domain, unsigned int virq,
> +				unsigned int nr_irqs, void *arg)
> +{
> +	int ret;
> +	unsigned int i, type;
> +	unsigned long hwirq = 0;
> +	struct eiointc *priv = domain->host_data;
> +
> +	ret = irq_domain_translate_onecell(domain, arg, &hwirq, &type);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		irq_domain_set_info(domain, virq + i, hwirq + i, &eiointc_irq_chip,
> +					priv, handle_edge_irq, NULL, NULL);
> +	}
> +
> +	return 0;
> +}
> +
> +static void eiointc_domain_free(struct irq_domain *domain, unsigned int virq,
> +				unsigned int nr_irqs)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		struct irq_data *d = irq_domain_get_irq_data(domain, virq + i);
> +
> +		irq_set_handler(virq + i, NULL);
> +		irq_domain_reset_irq_data(d);
> +	}
> +}
> +
> +static const struct irq_domain_ops eiointc_domain_ops = {
> +	.translate	= irq_domain_translate_onecell,
> +	.alloc		= eiointc_domain_alloc,
> +	.free		= eiointc_domain_free,
> +};
> +
> +static int eiointc_suspend(void)
> +{
> +	return 0;
> +}
> +
> +static bool is_eiointc_irq(struct irq_data *irq_data)
> +{
> +	int i;
> +	struct irq_domain *parent;
> +
> +	for (parent = irq_data->domain; parent; parent = parent->parent) {
> +		for (i = 0; i < nr_pics; i++) {
> +			if (parent == eiointc_priv[i]->eiointc_domain)
> +				return true;
> +		}
> +	}
> +
> +	return false;
> +}
> +
> +static void eiointc_resume(void)
> +{
> +	int i;
> +	struct irq_desc *desc;
> +	struct irq_data *irq_data;
> +
> +	eiointc_router_init(0);
> +
> +	for (i = 0; i < NR_IRQS; i++) {

No. Never.

> +		desc = irq_to_desc(i);
> +		if (desc && desc->handle_irq && desc->handle_irq != handle_bad_irq) {
> +			irq_data = &desc->irq_data;
> +			if (!is_eiointc_irq(irq_data))
> +				continue;
> +
> +			eiointc_set_irq_affinity(irq_data, irq_data->common->affinity, 0);
> +		}

If you need to restore some state, track the interrupts that actually
matter. But this is... just not on.

	M.

-- 
Without deviation from the norm, progress is not possible.

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