Subject: Re: [PATCH V8 3/3] irqchip: qcom: Add IRQ combiner driver
To: Agustin Vega-Frias <agustinv@codeaurora.org>,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, rjw@rjwysocki.net,
        lenb@kernel.org, tglx@linutronix.de, jason@lakedaemon.net
References: <1480460259-8585-1-git-send-email-agustinv@codeaurora.org>
 <1480460259-8585-4-git-send-email-agustinv@codeaurora.org>
Cc: timur@codeaurora.org, cov@codeaurora.org, agross@codeaurora.org,
        harba@codeaurora.org, jcm@redhat.com, msalter@redhat.com,
        mlangsdo@redhat.com, ahs3@redhat.com, astone@redhat.com,
        graeme.gregory@linaro.org, guohanjun@huawei.com,
        charles.garcia-tobin@arm.com
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <b009635d-8a10-5e22-4438-0019d79d01d3@arm.com>
Date: Wed, 7 Dec 2016 18:16:33 +0000
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Hi Agustin,

On 29/11/16 22:57, Agustin Vega-Frias wrote:
> Driver for interrupt combiners in the Top-level Control and Status
> Registers (TCSR) hardware block in Qualcomm Technologies chips.
> 
> An interrupt combiner in this block combines a set of interrupts by
> OR'ing the individual interrupt signals into a summary interrupt
> signal routed to a parent interrupt controller, and provides read-
> only, 32-bit registers to query the status of individual interrupts.
> The status bit for IRQ n is bit (n % 32) within register (n / 32)
> of the given combiner. Thus, each combiner can be described as a set
> of register offsets and the number of IRQs managed.
> 
> Signed-off-by: Agustin Vega-Frias <agustinv@codeaurora.org>
> ---
>  drivers/irqchip/Kconfig             |   8 +
>  drivers/irqchip/Makefile            |   1 +
>  drivers/irqchip/qcom-irq-combiner.c | 337 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 346 insertions(+)
>  create mode 100644 drivers/irqchip/qcom-irq-combiner.c
> 
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index bc0af33..610f902 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -279,3 +279,11 @@ config EZNPS_GIC
>  config STM32_EXTI
>  	bool
>  	select IRQ_DOMAIN
> +
> +config QCOM_IRQ_COMBINER
> +	bool "QCOM IRQ combiner support"
> +	depends on ARCH_QCOM
> +	select IRQ_DOMAIN
> +	help
> +	  Say yes here to add support for the IRQ combiner devices embedded
> +	  in Qualcomm Technologies chips.
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index e4dbfc8..1818a0b 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -74,3 +74,4 @@ obj-$(CONFIG_LS_SCFG_MSI)		+= irq-ls-scfg-msi.o
>  obj-$(CONFIG_EZNPS_GIC)			+= irq-eznps.o
>  obj-$(CONFIG_ARCH_ASPEED)		+= irq-aspeed-vic.o
>  obj-$(CONFIG_STM32_EXTI) 		+= irq-stm32-exti.o
> +obj-$(CONFIG_QCOM_IRQ_COMBINER)		+= qcom-irq-combiner.o
> diff --git a/drivers/irqchip/qcom-irq-combiner.c b/drivers/irqchip/qcom-irq-combiner.c
> new file mode 100644
> index 0000000..fc25251
> --- /dev/null
> +++ b/drivers/irqchip/qcom-irq-combiner.c
> @@ -0,0 +1,337 @@
> +/* Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +/*
> + * Driver for interrupt combiners in the Top-level Control and Status
> + * Registers (TCSR) hardware block in Qualcomm Technologies chips.
> + * An interrupt combiner in this block combines a set of interrupts by
> + * OR'ing the individual interrupt signals into a summary interrupt
> + * signal routed to a parent interrupt controller, and provides read-
> + * only, 32-bit registers to query the status of individual interrupts.
> + * The status bit for IRQ n is bit (n % 32) within register (n / 32)
> + * of the given combiner. Thus, each combiner can be described as a set
> + * of register offsets and the number of IRQs managed.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/irqdomain.h>
> +#include <linux/platform_device.h>
> +
> +#define REG_SIZE 32
> +
> +struct combiner_reg {
> +	void __iomem *addr;
> +	unsigned long mask;
> +};
> +
> +struct combiner {
> +	struct irq_chip     irq_chip;
> +	struct irq_domain   *domain;
> +	int                 parent_irq;
> +	u32                 nirqs;
> +	u32                 nregs;
> +	struct combiner_reg regs[0];
> +};
> +
> +static inline u32 irq_register(int irq)
> +{
> +	return irq / REG_SIZE;
> +}
> +
> +static inline u32 irq_bit(int irq)
> +{
> +	return irq % REG_SIZE;
> +
> +}
> +
> +static inline int irq_nr(u32 reg, u32 bit)
> +{
> +	return reg * REG_SIZE + bit;
> +}
> +
> +/*
> + * Handler for the cascaded IRQ.
> + */
> +static void combiner_handle_irq(struct irq_desc *desc)
> +{
> +	struct combiner *combiner = irq_desc_get_handler_data(desc);
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	u32 reg;
> +
> +	chained_irq_enter(chip, desc);
> +
> +	for (reg = 0; reg < combiner->nregs; reg++) {
> +		int virq;
> +		int hwirq;
> +		u32 bit;
> +		u32 status;
> +
> +		if (combiner->regs[reg].mask == 0)
> +			continue;
> +
> +		status = readl_relaxed(combiner->regs[reg].addr);
> +		status &= combiner->regs[reg].mask;
> +
> +		while (status) {
> +			bit = __ffs(status);
> +			status &= ~(1 << bit);
> +			hwirq = irq_nr(reg, bit);
> +			virq = irq_find_mapping(combiner->domain, hwirq);
> +			if (virq >= 0)
> +				generic_handle_irq(virq);
> +
> +		}
> +	}
> +
> +	chained_irq_exit(chip, desc);
> +}
> +
> +/*
> + * irqchip callbacks
> + */
> +
> +static void combiner_irq_chip_mask_irq(struct irq_data *data)
> +{
> +	struct combiner *combiner = irq_data_get_irq_chip_data(data);
> +	struct combiner_reg *reg = combiner->regs + irq_register(data->hwirq);
> +
> +	clear_bit(irq_bit(data->hwirq), &reg->mask);
> +}
> +
> +static void combiner_irq_chip_unmask_irq(struct irq_data *data)
> +{
> +	struct combiner *combiner = irq_data_get_irq_chip_data(data);
> +	struct combiner_reg *reg = combiner->regs + irq_register(data->hwirq);
> +
> +	set_bit(irq_bit(data->hwirq), &reg->mask);
> +}
> +
> +/*
> + * irq_domain_ops callbacks
> + */
> +
> +static int combiner_irq_map(struct irq_domain *domain, unsigned int irq,
> +				   irq_hw_number_t hwirq)
> +{
> +	struct combiner *combiner = domain->host_data;
> +
> +	if (hwirq >= combiner->nirqs)
> +		return -EINVAL;
> +
> +	irq_set_chip_and_handler(irq, &combiner->irq_chip, handle_level_irq);
> +	irq_set_chip_data(irq, combiner);
> +	irq_set_parent(irq, combiner->parent_irq);

Do you really need this irq_set_parent? This only makes sense if you're
resending edge interrupts, and you seem to be level only.

> +	irq_set_noprobe(irq);
> +	return 0;
> +}
> +
> +static void combiner_irq_unmap(struct irq_domain *domain, unsigned int irq)
> +{
> +	irq_set_chip_and_handler(irq, NULL, NULL);
> +	irq_set_chip_data(irq, NULL);
> +	irq_set_parent(irq, -1);

All of this should probably be replaced with a call to
irq_domain_reset_irq_data().

> +}
> +
> +#ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY

Is there any case where this is not valid?

> +static int combiner_irq_translate(struct irq_domain *d, struct irq_fwspec *fws,
> +				  unsigned long *hwirq, unsigned int *type)
> +{
> +	if (is_acpi_node(fws->fwnode)) {
> +		if (fws->param_count != 2)
> +			return -EINVAL;
> +
> +		*hwirq = fws->param[0];
> +		*type = fws->param[1];

Given that you're only handling level interrupts, shouldn't you abort if
detecting an edge interrupt?

> +		return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +#endif
> +
> +static const struct irq_domain_ops domain_ops = {
> +	.map = combiner_irq_map,
> +	.unmap = combiner_irq_unmap,
> +#ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
> +	.translate = combiner_irq_translate
> +#endif
> +};
> +
> +/*
> + * Device probing
> + */
> +
> +#ifdef CONFIG_ACPI
> +
> +static acpi_status count_registers_cb(struct acpi_resource *ares, void *context)
> +{
> +	int *count = context;
> +
> +	if (ares->type == ACPI_RESOURCE_TYPE_GENERIC_REGISTER)
> +		++(*count);
> +	return AE_OK;
> +}
> +
> +static int count_registers(struct platform_device *pdev)
> +{
> +	struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
> +	acpi_status status;
> +	int count = 0;
> +
> +	if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
> +		return -EINVAL;
> +
> +	status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
> +				     count_registers_cb, &count);
> +	if (ACPI_FAILURE(status))
> +		return -EINVAL;
> +	return count;
> +}
> +
> +struct get_registers_context {
> +	struct device *dev;
> +	struct combiner *combiner;
> +	int err;
> +};
> +
> +static acpi_status get_registers_cb(struct acpi_resource *ares, void *context)
> +{
> +	struct get_registers_context *ctx = context;
> +	struct acpi_resource_generic_register *reg;
> +	phys_addr_t paddr;
> +	void __iomem *vaddr;
> +
> +	if (ares->type != ACPI_RESOURCE_TYPE_GENERIC_REGISTER)
> +		return AE_OK;
> +
> +	reg = &ares->data.generic_reg;
> +	paddr = reg->address;
> +	if ((reg->space_id != ACPI_SPACE_MEM) ||
> +	    (reg->bit_offset != 0) ||
> +	    (reg->bit_width > REG_SIZE)) {
> +		dev_err(ctx->dev, "Bad register resource @%pa\n", &paddr);
> +		ctx->err = -EINVAL;
> +		return AE_ERROR;
> +	}
> +
> +	vaddr = devm_ioremap(ctx->dev, reg->address, REG_SIZE);
> +	if (IS_ERR(vaddr)) {
> +		dev_err(ctx->dev, "Can't map register @%pa\n", &paddr);
> +		ctx->err = PTR_ERR(vaddr);
> +		return AE_ERROR;
> +	}
> +
> +	ctx->combiner->regs[ctx->combiner->nregs].addr = vaddr;
> +	ctx->combiner->nirqs += reg->bit_width;
> +	ctx->combiner->nregs++;
> +	return AE_OK;
> +}
> +
> +static int get_registers(struct platform_device *pdev, struct combiner *comb)
> +{
> +	struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
> +	acpi_status status;
> +	struct get_registers_context ctx;
> +
> +	if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
> +		return -EINVAL;
> +
> +	ctx.dev = &pdev->dev;
> +	ctx.combiner = comb;
> +	ctx.err = 0;
> +
> +	status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
> +				     get_registers_cb, &ctx);
> +	if (ACPI_FAILURE(status))
> +		return ctx.err;
> +	return 0;
> +}
> +
> +#else /* !CONFIG_ACPI */
> +
> +static int count_registers(struct platform_device *pdev)
> +{
> +	return -EINVAL;
> +}
> +
> +static int get_registers(struct platform_device *pdev, struct combiner *comb)
> +{
> +	return -EINVAL;
> +}

So this driver is obviously ACPI only. Can't you just get rid of these,
of the #ifdef CONFIG_ACPI, and simply make it depend on ACPI?

> +
> +#endif
> +
> +static int __init combiner_probe(struct platform_device *pdev)
> +{
> +	struct combiner *combiner;
> +	size_t alloc_sz;
> +	u32 nregs;
> +	int err;
> +
> +	nregs = count_registers(pdev);
> +	if (nregs <= 0) {
> +		dev_err(&pdev->dev, "Error reading register resources\n");
> +		return -EINVAL;
> +	}
> +
> +	alloc_sz = sizeof(*combiner) + sizeof(struct combiner_reg) * nregs;
> +	combiner = devm_kzalloc(&pdev->dev, alloc_sz, GFP_KERNEL);
> +	if (!combiner)
> +		return -ENOMEM;
> +
> +	err = get_registers(pdev, combiner);
> +	if (err < 0)
> +		return err;
> +
> +	combiner->parent_irq = platform_get_irq(pdev, 0);
> +	if (combiner->parent_irq <= 0) {
> +		dev_err(&pdev->dev, "Error getting IRQ resource\n");
> +		return -EINVAL;

Can you ever get in a situation where it'd be more sensible to return
-EPROBE_DEFER? I'm thinking of a case where you'd have this irq chip
cascaded into another one, which is not present yet?

> +	}
> +
> +	combiner->domain = irq_domain_create_linear(
> +		pdev->dev.fwnode, combiner->nirqs, &domain_ops, combiner);

On a single line, please. Do no listen to the checkpatch police that
will tell you otherwise. It really hurt my eyes to see this opening
bracket and *nothing* after that.

> +	if (!combiner->domain)
> +		/* Errors printed by irq_domain_create_linear */
> +		return -ENODEV;
> +
> +	irq_set_chained_handler_and_data(combiner->parent_irq,
> +					 combiner_handle_irq, combiner);
> +	combiner->irq_chip.irq_mask = combiner_irq_chip_mask_irq;
> +	combiner->irq_chip.irq_unmask = combiner_irq_chip_unmask_irq;
> +	combiner->irq_chip.name = pdev->name;

Arghh. Please don't do that. Once you've called irq_set_chained_*, the
interrupt is live, and can be requested. Unlikely, but still. In
general, feeding uninitialized data to a function is pretty bad.

Also, do you really need to show pdev->name in /proc/cpuinfo? Just make
the irq_chip structure static, outside of combiner, and have "QCOM80B1"
(or something of your liking) as the name once and for all.

> +
> +	dev_info(&pdev->dev, "Initialized with [p=%d,n=%d,r=%p]\n",
> +		 combiner->parent_irq, combiner->nirqs, combiner->regs[0].addr);
> +	return 0;
> +}
> +
> +static const struct acpi_device_id qcom_irq_combiner_acpi_match[] = {
> +	{ "QCOM80B1", },
> +	{ }
> +};
> +
> +static struct platform_driver qcom_irq_combiner_probe = {
> +	.driver = {
> +		.name = "qcom-irq-combiner",
> +		.owner = THIS_MODULE,
> +		.acpi_match_table = ACPI_PTR(qcom_irq_combiner_acpi_match),
> +	},
> +	.probe = combiner_probe,
> +};
> +
> +static int __init register_qcom_irq_combiner(void)
> +{
> +	return platform_driver_register(&qcom_irq_combiner_probe);
> +}
> +device_initcall(register_qcom_irq_combiner);
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...