Date:   Tue, 09 Mar 2021 10:58:09 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Álvaro Fernández Rojas <noltari@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jonas Gorski <jonas.gorski@...il.com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com, linux-mips@...r.kernel.org
Subject: Re: [PATCH v2 2/2] irqchip: add support for BCM6345 external interrupt controller

On Wed, 24 Feb 2021 07:56:40 +0000,
Álvaro Fernández Rojas <noltari@...il.com> wrote:
> 
> This interrupt controller is present on bcm63xx SoCs in order to generate
> interrupts based on GPIO status changes.
> 
> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>
> Signed-off-by: Jonas Gorski <jonas.gorski@...il.com>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  v3: no changes.
>  v2: no changes.
> 
>  drivers/irqchip/Kconfig           |   4 +
>  drivers/irqchip/Makefile          |   1 +
>  drivers/irqchip/irq-bcm6345-ext.c | 271 ++++++++++++++++++++++++++++++
>  3 files changed, 276 insertions(+)
>  create mode 100644 drivers/irqchip/irq-bcm6345-ext.c
> 
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index e74fa206240a..eaa101939a34 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -113,6 +113,10 @@ config I8259
>  	bool
>  	select IRQ_DOMAIN
>  
> +config BCM6345_EXT_IRQ
> +	bool "BCM6345 External IRQ Controller"
> +	select IRQ_DOMAIN
> +
>  config BCM6345_L1_IRQ
>  	bool
>  	select GENERIC_IRQ_CHIP
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index c59b95a0532c..3cba65bc0aa5 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_XTENSA_MX)			+= irq-xtensa-mx.o
>  obj-$(CONFIG_XILINX_INTC)		+= irq-xilinx-intc.o
>  obj-$(CONFIG_IRQ_CROSSBAR)		+= irq-crossbar.o
>  obj-$(CONFIG_SOC_VF610)			+= irq-vf610-mscm-ir.o
> +obj-$(CONFIG_BCM6345_EXT_IRQ)		+= irq-bcm6345-ext.o
>  obj-$(CONFIG_BCM6345_L1_IRQ)		+= irq-bcm6345-l1.o
>  obj-$(CONFIG_BCM7038_L1_IRQ)		+= irq-bcm7038-l1.o
>  obj-$(CONFIG_BCM7120_L2_IRQ)		+= irq-bcm7120-l2.o
> diff --git a/drivers/irqchip/irq-bcm6345-ext.c b/drivers/irqchip/irq-bcm6345-ext.c
> new file mode 100644
> index 000000000000..5721ac8de295
> --- /dev/null
> +++ b/drivers/irqchip/irq-bcm6345-ext.c
> @@ -0,0 +1,271 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Broadcom BCM6345 style external interrupt controller driver
> + *
> + * Copyright (C) 2021 Álvaro Fernández Rojas <noltari@...il.com>
> + * Copyright (C) 2014 Jonas Gorski <jonas.gorski@...il.com>
> + */
> +
> +#include <linux/ioport.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/kernel.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#define MAX_IRQS		4
> +
> +#define EXTIRQ_CFG_SENSE	0
> +#define EXTIRQ_CFG_STAT		1
> +#define EXTIRQ_CFG_CLEAR	2
> +#define EXTIRQ_CFG_MASK		3
> +#define EXTIRQ_CFG_BOTHEDGE	4
> +#define EXTIRQ_CFG_LEVELSENSE	5
> +
> +struct intc_data {
> +	struct irq_chip chip;
> +	struct irq_domain *domain;
> +	raw_spinlock_t lock;
> +
> +	int parent_irq[MAX_IRQS];
> +	void __iomem *reg;
> +	int shift;
> +	unsigned int toggle_clear_on_ack:1;

Please use the bool type.

> +};
> +
> +static void bcm6345_ext_intc_irq_handle(struct irq_desc *desc)
> +{
> +	struct intc_data *data = irq_desc_get_handler_data(desc);
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	unsigned int irq = irq_desc_get_irq(desc);
> +	unsigned int idx;
> +
> +	chained_irq_enter(chip, desc);
> +
> +	for (idx = 0; idx < MAX_IRQS; idx++) {
> +		if (data->parent_irq[idx] != irq)
> +			continue;
> +
> +		generic_handle_irq(irq_find_mapping(data->domain, idx));

One parent IRQ per input? Why isn't this a hierarchical interrupt
controller? Even *if* this really has to be a chained interrupt
controller, I'm sure there are better ways to identify the input then
this loop (offset from a base, for example).

> +	}
> +
> +	chained_irq_exit(chip, desc);
> +}
> +
> +static void bcm6345_ext_intc_irq_ack(struct irq_data *data)
> +{
> +	struct intc_data *priv = data->domain->host_data;
> +	irq_hw_number_t hwirq = irqd_to_hwirq(data);
> +	u32 reg;
> +
> +	raw_spin_lock(&priv->lock);
> +	reg = __raw_readl(priv->reg);
> +	__raw_writel(reg | (1 << (hwirq + EXTIRQ_CFG_CLEAR * priv->shift)),
> +		     priv->reg);
> +	if (priv->toggle_clear_on_ack)

Under what condition do you need this?

> +		__raw_writel(reg, priv->reg);
> +	raw_spin_unlock(&priv->lock);
> +}
> +
> +static void bcm6345_ext_intc_irq_mask(struct irq_data *data)
> +{
> +	struct intc_data *priv = data->domain->host_data;
> +	irq_hw_number_t hwirq = irqd_to_hwirq(data);
> +	u32 reg;
> +
> +	raw_spin_lock(&priv->lock);
> +	reg = __raw_readl(priv->reg);
> +	reg &= ~(1 << (hwirq + EXTIRQ_CFG_MASK * priv->shift));
> +	__raw_writel(reg, priv->reg);
> +	raw_spin_unlock(&priv->lock);
> +}
> +
> +static void bcm6345_ext_intc_irq_unmask(struct irq_data *data)
> +{
> +	struct intc_data *priv = data->domain->host_data;
> +	irq_hw_number_t hwirq = irqd_to_hwirq(data);
> +	u32 reg;
> +
> +	raw_spin_lock(&priv->lock);
> +	reg = __raw_readl(priv->reg);
> +	reg |= 1 << (hwirq + EXTIRQ_CFG_MASK * priv->shift);
> +	__raw_writel(reg, priv->reg);
> +	raw_spin_unlock(&priv->lock);
> +}
> +
> +static int bcm6345_ext_intc_set_type(struct irq_data *data,
> +				     unsigned int flow_type)
> +{
> +	struct intc_data *priv = data->domain->host_data;
> +	irq_hw_number_t hwirq = irqd_to_hwirq(data);
> +	bool levelsense = 0, sense = 0, bothedge = 0;
> +	u32 reg;
> +
> +	flow_type &= IRQ_TYPE_SENSE_MASK;
> +
> +	if (flow_type == IRQ_TYPE_NONE)

You should never get NONE. If you have that value here, that's
probably a bug somewhere else.

> +		flow_type = IRQ_TYPE_LEVEL_LOW;
> +
> +	switch (flow_type) {
> +	case IRQ_TYPE_EDGE_BOTH:
> +		bothedge = 1;
> +		break;
> +
> +	case IRQ_TYPE_EDGE_RISING:
> +		sense = 1;
> +		break;
> +
> +	case IRQ_TYPE_EDGE_FALLING:
> +		break;
> +
> +	case IRQ_TYPE_LEVEL_HIGH:
> +		levelsense = 1;
> +		sense = 1;
> +		break;
> +
> +	case IRQ_TYPE_LEVEL_LOW:
> +		levelsense = 1;
> +		break;
> +
> +	default:
> +		pr_err("bogus flow type combination given!\n");
> +		return -EINVAL;

How can this happen?

> +	}
> +
> +	raw_spin_lock(&priv->lock);
> +	reg = __raw_readl(priv->reg);
> +
> +	if (levelsense)
> +		reg |= 1 << (hwirq + EXTIRQ_CFG_LEVELSENSE * priv->shift);
> +	else
> +		reg &= ~(1 << (hwirq + EXTIRQ_CFG_LEVELSENSE * priv->shift));
> +	if (sense)
> +		reg |= 1 << (hwirq + EXTIRQ_CFG_SENSE * priv->shift);
> +	else
> +		reg &= ~(1 << (hwirq + EXTIRQ_CFG_SENSE * priv->shift));
> +	if (bothedge)
> +		reg |= 1 << (hwirq + EXTIRQ_CFG_BOTHEDGE * priv->shift);
> +	else
> +		reg &= ~(1 << (hwirq + EXTIRQ_CFG_BOTHEDGE * priv->shift));

So all these levelsense, sense and bothedge variables are already
contained in flow_type. Why the need to reinvent the wheel?

> +
> +	__raw_writel(reg, priv->reg);
> +	raw_spin_unlock(&priv->lock);
> +
> +	irqd_set_trigger_type(data, flow_type);
> +	if (flow_type & (IRQ_TYPE_LEVEL_LOW | IRQ_TYPE_LEVEL_HIGH))
> +		irq_set_handler_locked(data, handle_level_irq);
> +	else
> +		irq_set_handler_locked(data, handle_edge_irq);
> +
> +	return 0;
> +}
> +
> +static int bcm6345_ext_intc_map(struct irq_domain *d, unsigned int irq,
> +				irq_hw_number_t hw)
> +{
> +	struct intc_data *priv = d->host_data;
> +
> +	irq_set_chip_and_handler(irq, &priv->chip, handle_level_irq);
> +
> +	return 0;
> +}
> +
> +static const struct irq_domain_ops bcm6345_ext_domain_ops = {
> +	.xlate = irq_domain_xlate_twocell,
> +	.map = bcm6345_ext_intc_map,
> +};
> +
> +static int __init bcm6345_ext_intc_init(struct device_node *node,
> +					int num_irqs, int *irqs,
> +					void __iomem *reg, int shift,
> +					bool toggle_clear_on_ack)
> +{
> +	struct intc_data *data;
> +	unsigned int i;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	raw_spin_lock_init(&data->lock);
> +
> +	for (i = 0; i < num_irqs; i++) {
> +		data->parent_irq[i] = irqs[i];
> +
> +		irq_set_handler_data(irqs[i], data);
> +		irq_set_chained_handler(irqs[i], bcm6345_ext_intc_irq_handle);
> +	}
> +
> +	data->reg = reg;
> +	data->shift = shift;
> +	data->toggle_clear_on_ack = toggle_clear_on_ack;
> +
> +	data->chip.name = "bcm6345-ext-intc";
> +	data->chip.irq_ack = bcm6345_ext_intc_irq_ack;
> +	data->chip.irq_mask = bcm6345_ext_intc_irq_mask;
> +	data->chip.irq_unmask = bcm6345_ext_intc_irq_unmask;
> +	data->chip.irq_set_type = bcm6345_ext_intc_set_type;
> +
> +	data->domain = irq_domain_add_simple(node, num_irqs, 0,
> +					     &bcm6345_ext_domain_ops, data);

Consider using irq_domain_add_linear(), given that you don't seem to
care about the first interrupt number.

> +	if (!data->domain) {
> +		kfree(data);
> +		return -ENOMEM;
> +	}

At this point, you have registered a bunch of chained handlers with
data structures that you have freed. What could possibly go wrong?

> +
> +	return 0;
> +}
> +
> +static int __init bcm6345_ext_intc_of_init(struct device_node *node,
> +					   struct device_node *parent)
> +{
> +	int num_irqs, ret = -EINVAL;
> +	unsigned i;
> +	void __iomem *base;
> +	int irqs[MAX_IRQS] = { 0 };
> +	u32 shift;
> +	bool toggle_clear_on_ack = false;
> +
> +	num_irqs = of_irq_count(node);
> +
> +	if (!num_irqs || num_irqs > MAX_IRQS)
> +		return -EINVAL;
> +
> +	if (of_property_read_u32(node, "brcm,field-width", &shift))
> +		shift = 4;

Why this default? Given that it is a new driver without any backward
compatibility requirement, either make the property mandatory or get
rid of it.

> +
> +	/* On BCM6318 setting CLEAR seems to continuously mask interrupts */
> +	if (of_device_is_compatible(node, "brcm,bcm6318-ext-intc"))
> +		toggle_clear_on_ack = true;

Seems? What does the documentation says about this?

> +
> +	for (i = 0; i < num_irqs; i++) {
> +		irqs[i] = irq_of_parse_and_map(node, i);
> +		if (!irqs[i])
> +			return -ENOMEM;
> +	}
> +
> +	base = of_iomap(node, 0);
> +	if (!base)
> +		return -ENXIO;
> +
> +	ret = bcm6345_ext_intc_init(node, num_irqs, irqs, base, shift,
> +				    toggle_clear_on_ack);
> +	if (!ret)
> +		return 0;
> +
> +	iounmap(base);
> +
> +	for (i = 0; i < num_irqs; i++)
> +		irq_dispose_mapping(irqs[i]);
> +
> +	return ret;
> +}
> +
> +IRQCHIP_DECLARE(bcm6318_ext_intc, "brcm,bcm6318-ext-intc",
> +		bcm6345_ext_intc_of_init);
> +IRQCHIP_DECLARE(bcm6345_ext_intc, "brcm,bcm6345-ext-intc",
> +		bcm6345_ext_intc_of_init);
> -- 
> 2.20.1
> 
> 

Thanks,

	M.

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

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