Message-ID: <78bfd90d47200347628f7dd98451122f@codeaurora.org>
Date:   Tue, 13 Dec 2016 10:23:01 -0500
From:   Agustin Vega-Frias <agustinv@...eaurora.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, rjw@...ysocki.net,
        lenb@...nel.org, tglx@...utronix.de, jason@...edaemon.net,
        timur@...eaurora.org, cov@...eaurora.org, agross@...eaurora.org,
        harba@...eaurora.org, jcm@...hat.com, msalter@...hat.com,
        mlangsdo@...hat.com, ahs3@...hat.com, astone@...hat.com,
        graeme.gregory@...aro.org, guohanjun@...wei.com,
        charles.garcia-tobin@....com
Subject: Re: [PATCH V8 3/3] irqchip: qcom: Add IRQ combiner driver

On 2016-12-07 13:16, Marc Zyngier wrote:
> 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@...eaurora.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.

OK, I'll take a look.

> 
>> +	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().

Will do.

> 
>> +}
>> +
>> +#ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
> 
> Is there any case where this is not valid?

What do you mean? Are you asking why is this under a preprocessor
conditional? If so I did it to be on the safe side since translate
in struct irq_domain_ops under that conditional.

> 
>> +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?

I'll add the check.

> 
>> +		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?

Good point, will do.

> 
>> +
>> +#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?

Not in the current architecture, but I agree it would accommodate other
use cases. I will change it to return -EPROBE_DEFER.

> 
>> +	}
>> +
>> +	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.

Will do.

> 
>> +	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.

I'll look at this.

Thanks for the detailed feedback.

Agustin.

> 
>> +
>> +	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...

-- 
Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a 
Linux Foundation Collaborative Project.

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