Date:   Sat, 06 Oct 2018 10:55:13 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Lokesh Vutla <lokeshvutla@...com>
Cc:     Nishanth Menon <nm@...com>, Tero Kristo <t-kristo@...com>,
        <tglx@...utronix.de>, <jason@...edaemon.net>,
        Rob Herring <robh+dt@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Device Tree Mailing List <devicetree@...r.kernel.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH 2/2] irqchip: ti-sci-intr: Add support for Interrupt Router driver

Hi Lokesh,

On Sat, 06 Oct 2018 08:28:12 +0100,
Lokesh Vutla <lokeshvutla@...com> wrote:
> 
> Texas Instruments' K3 generation SoCs has an IP Interrupt Router
> that does allows for multiplexing of input interrupts to host
> interrupt controller. Interrupt Router inputs are either from a
> peripheral or from an Interrupt Aggregator which is another
> interrupt controller.
> 
> Configuration of the interrupt router registers can only be done by
> a system co-processor and the driver needs to send a message to this
> co processor over TISCI protocol.

I assume that this co-processor only deals with the routing itself,
and doesn't need to be talked to during interrupt processing, right?

> 
> Add support for Interrupt Router driver over TISCI protocol.
> 
> Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
> ---
>  MAINTAINERS                       |   1 +
>  drivers/irqchip/Kconfig           |  11 +
>  drivers/irqchip/Makefile          |   1 +
>  drivers/irqchip/irq-ti-sci-intr.c | 325 ++++++++++++++++++++++++++++++
>  4 files changed, 338 insertions(+)
>  create mode 100644 drivers/irqchip/irq-ti-sci-intr.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a23778b68d74..cf3c834f8cee 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14626,6 +14626,7 @@ F:	Documentation/devicetree/bindings/clock/ti,sci-clk.txt
>  F:	drivers/clk/keystone/sci-clk.c
>  F:	drivers/reset/reset-ti-sci.c
>  F:	Documentation/devicetree/bindings/interrupt-controller/ti,sci-intr.txt
> +F:	drivers/irqchip/irq-ti-sci-intr.c
>  
>  THANKO'S RAREMONO AM/FM/SW RADIO RECEIVER USB DRIVER
>  M:	Hans Verkuil <hverkuil@...all.nl>
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index 96451b581452..9a965fe22043 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -374,6 +374,17 @@ config QCOM_PDC
>  	  Power Domain Controller driver to manage and configure wakeup
>  	  IRQs for Qualcomm Technologies Inc (QTI) mobile chips.
>  
> +config TI_SCI_INTR_IRQCHIP
> +	tristate "TISCI based Interrupt Router irqchip driver"
> +	depends on TI_SCI_PROTOCOL && ARCH_K3
> +	select IRQ_DOMAIN
> +	select IRQ_DOMAIN_HIERARCHY
> +	help
> +	  This enables the irqchip driver support for K3 Interrupt router
> +	  over TI System Control Interface available on some new TI's SoCs.
> +	  If you wish to use interrupt router irq resources managed by the
> +	  TI System Controller, say Y here. Otherwise, say N.

I don't really see the point of making this user-selectable. If you're
compiling support for a given platform, this platform configuration
fragment should itself select the necessary dependencies for the
system to work as expected. Here, you are leaving the choice to the
user, with a 50% chance of getting a system that doesn't boot...

> +
>  endmenu
>  
>  config SIFIVE_PLIC
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index b822199445ff..44bf65606d60 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -89,3 +89,4 @@ obj-$(CONFIG_GOLDFISH_PIC) 		+= irq-goldfish-pic.o
>  obj-$(CONFIG_NDS32)			+= irq-ativic32.o
>  obj-$(CONFIG_QCOM_PDC)			+= qcom-pdc.o
>  obj-$(CONFIG_SIFIVE_PLIC)		+= irq-sifive-plic.o
> +obj-$(CONFIG_TI_SCI_INTR_IRQCHIP)	+= irq-ti-sci-intr.o
> diff --git a/drivers/irqchip/irq-ti-sci-intr.c b/drivers/irqchip/irq-ti-sci-intr.c
> new file mode 100644
> index 000000000000..f04fe6da1b09
> --- /dev/null
> +++ b/drivers/irqchip/irq-ti-sci-intr.c
> @@ -0,0 +1,325 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Texas Instruments' K3 Interrupt Router irqchip driver
> + *
> + * Copyright (C) 2018 Texas Instruments Incorporated - http://www.ti.com/
> + *	Lokesh Vutla <lokeshvutla@...com>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/irqchip.h>
> +#include <linux/of_platform.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/irqdomain.h>
> +#include <linux/soc/ti/ti_sci_protocol.h>
> +
> +#define TI_SCI_DEV_ID_MASK	0xffff
> +#define TI_SCI_DEV_ID_SHIFT	16
> +#define TI_SCI_IRQ_ID_MASK	0xffff
> +#define TI_SCI_IRQ_ID_SHIFT	0
> +#define TI_SCI_IS_EVENT_IRQ	BIT(31)
> +
> +#define HWIRQ_TO_DEVID(HWIRQ)	(((HWIRQ) >> (TI_SCI_DEV_ID_SHIFT)) & \
> +				 (TI_SCI_DEV_ID_MASK))
> +#define HWIRQ_TO_IRQID(HWIRQ)	((HWIRQ) & (TI_SCI_IRQ_ID_MASK))

nit: s/(HWIRQ)/(hwirq)/g

> +
> +/**
> + * struct ti_sci_intr_irq_domain - Structure representing a TISCI based
> + *				   Interrupt Router IRQ domain.
> + * @sci:	Pointer to TISCI handle
> + * @dst_irq:	TISCI resource pointer representing destination irq controller.
> + * @dst_id:	TISCI device ID of the destination irq controller.
> + */
> +struct ti_sci_intr_irq_domain {
> +	const struct ti_sci_handle *sci;
> +	struct ti_sci_resource *dst_irq;
> +	u16 dst_id;
> +};
> +
> +/**
> + * struct ti_sci_intr_irq_desc - Description of an Interrupt Router IRQ
> + * @src_id:		TISCI device ID of the IRQ source
> + * @src_index:		IRQ source index within the device.
> + * @dst_irq:		Destination host IRQ.
> + */
> +struct ti_sci_intr_irq_desc {
> +	u16 src_id;
> +	u16 src_index;
> +	u16 dst_irq;
> +};

Oh great. So this is reinventing the GICv3 ITS, only for SPIs. :-(

Now, this structure seems completely useless, see below.

> +
> +static struct irq_chip ti_sci_intr_irq_chip = {
> +	.name			= "INTR",
> +	.irq_eoi		= irq_chip_eoi_parent,
> +	.irq_mask		= irq_chip_mask_parent,
> +	.irq_unmask		= irq_chip_unmask_parent,
> +	.irq_retrigger		= irq_chip_retrigger_hierarchy,
> +	.irq_set_type		= irq_chip_set_type_parent,
> +	.irq_set_affinity	= irq_chip_set_affinity_parent,
> +};
> +
> +/**
> + * ti_sci_intr_irq_domain_translate() - Retrieve hwirq and type from
> + *					IRQ firmware specific handler.
> + * @domain:	Pointer to IRQ domain
> + * @fwspec:	Pointer to IRQ specific firmware structure
> + * @hwirq:	IRQ number identified by hardware
> + * @type:	IRQ type
> + *
> + * Return 0 if all went ok else appropriate error.
> + */
> +static int ti_sci_intr_irq_domain_translate(struct irq_domain *domain,
> +					    struct irq_fwspec *fwspec,
> +					    unsigned long *hwirq,
> +					    unsigned int *type)
> +{
> +	if (is_of_node(fwspec->fwnode)) {
> +		if (fwspec->param_count != 3)
> +			return -EINVAL;
> +
> +		*hwirq = ((fwspec->param[0] & TI_SCI_DEV_ID_MASK) <<
> +			  TI_SCI_DEV_ID_SHIFT) |
> +			 (fwspec->param[1] & TI_SCI_IRQ_ID_MASK);

Maybe it would make sense to have a macro that hides this:

      	       *hwirq = FWSPEC_TO_HWIRQ(fwspec);

> +		*type = fwspec->param[2];
> +
> +		return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static inline void ti_sci_intr_delete_desc(struct ti_sci_intr_irq_domain *intr,
> +					   struct ti_sci_intr_irq_desc *desc)
> +{
> +	intr->sci->ops.rm_irq_ops.free_direct_irq(intr->sci, desc->src_id,
> +						  desc->src_index,
> +						  intr->dst_id, desc->dst_irq);

This looks horrible. Why doesn't your firmware interface have a helper
functions that hides this? Something like:

	ti_sci_free_direct_irq(intr, src_id, src_index, dst_irq);

and you could even add some error checking.

> +	pr_debug("%s: IRQ deleted from src = %d, src_index = %d, to dst = %d, dst_irq = %d\n",
> +		 __func__, desc->src_id, desc->src_index, intr->dst_id,
> +		desc->dst_irq);

And put this where it belongs (in the helper function).

> +}
> +
> +/**
> + * ti_sci_intr_irq_domain_free() - Free the specified IRQs from the domain.
> + * @domain:	Domain to which the irqs belong
> + * @virq:	Linux virtual IRQ to be freed.
> + * @nr_irqs:	Number of continuous irqs to be freed
> + */
> +static void ti_sci_intr_irq_domain_free(struct irq_domain *domain,
> +					unsigned int virq, unsigned int nr_irqs)
> +{
> +	struct ti_sci_intr_irq_domain *intr = domain->host_data;
> +	struct ti_sci_intr_irq_desc *desc;
> +	struct irq_data *data;
> +	int i;
> +
> +	intr = domain->host_data;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		data = irq_domain_get_irq_data(domain, virq + i);
> +
> +		desc = irq_data_get_irq_chip_data(data);
> +
> +		ti_sci_intr_delete_desc(intr, desc);
> +		irq_domain_free_irqs_parent(domain, virq, 1);
> +		irq_domain_reset_irq_data(data);
> +		ti_sci_release_resource(intr->dst_irq, desc->dst_irq);
> +		kfree(desc);
> +	}
> +}
> +
> +/**
> + * allocate_gic_irq() - Allocate GIC specific IRQ
> + * @domain:	Point to the interrupt router IRQ domain
> + * @dev:	TISCI device IRQ generating the IRQ
> + * @irq:	IRQ offset within the device
> + * @flags:	Corresponding flags to the IRQ
> + *
> + * Returns pointer to irq descriptor if all went well else appropriate
> + * error pointer.
> + */
> +static struct ti_sci_intr_irq_desc *allocate_gic_irq(struct irq_domain *domain,
> +						     unsigned int virq,
> +						     u16 dev, u16 irq,
> +						     u32 flags)
> +{
> +	struct ti_sci_intr_irq_domain *intr = domain->host_data;
> +	struct ti_sci_intr_irq_desc *desc;
> +	struct irq_fwspec fwspec;
> +	int err;
> +
> +	if (!irq_domain_get_of_node(domain->parent))
> +		return ERR_PTR(-EINVAL);
> +
> +	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
> +	if (!desc)
> +		return ERR_PTR(-ENOMEM);
> +
> +	desc->src_id = dev;
> +	desc->src_index = irq;
> +	desc->dst_irq = ti_sci_get_free_resource(intr->dst_irq);

I don't think this structure serves any purpose. src_id and src_index
are just a decomposition of hwirq. dst_irq is the GIC interrupt, which
is stored... by the GIC driver. Also, it is worth realising that
you're allocating per-interrupt data, but none of the per-interrupt
callbacks are using it. In my book, that's a sure sign that this
structure is pointless.

Am I missing anything here?

> +
> +	fwspec.fwnode = domain->parent->fwnode;
> +	fwspec.param_count = 3;
> +	fwspec.param[0] = 0;	/* SPI */
> +	fwspec.param[1] = desc->dst_irq - 32; /* SPI offset */
> +	fwspec.param[2] = flags & IRQ_TYPE_SENSE_MASK;
> +
> +	err = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
> +	if (err)
> +		goto err_irqs;
> +
> +	pr_debug("%s: IRQ requested from src = %d, src_index = %d, to dst = %d, dst_irq = %d\n",
> +		 __func__, desc->src_id, desc->src_index, intr->dst_id,
> +		 desc->dst_irq);
> +
> +	err = intr->sci->ops.rm_irq_ops.set_direct_irq(intr->sci, desc->src_id,
> +						       desc->src_index,
> +						       intr->dst_id,
> +						       desc->dst_irq);

Same remarks about the horrible interface.

> +	if (err) {
> +		pr_err("%s: IRQ allocation failed from src = %d, src_index = %d to dst_id = %d, dst_irq = %d",
> +		       __func__, desc->src_id, desc->src_index, intr->dst_id,
> +		       desc->dst_irq);
> +		goto err_msg;
> +	}
> +
> +	return desc;
> +
> +err_msg:
> +	irq_domain_free_irqs_parent(domain, virq, 1);
> +err_irqs:
> +	ti_sci_release_resource(intr->dst_irq, desc->dst_irq);
> +	kfree(desc);
> +	return ERR_PTR(err);
> +}
> +
> +/**
> + * ti_sci_intr_irq_domain_alloc() - Allocate Interrupt router IRQs
> + * @domain:	Point to the interrupt router IRQ domain
> + * @virq:	Corresponding Linux virtual IRQ number
> + * @nr_irqs:	Continuous irqs to be allocated
> + * @data:	Pointer to firmware specifier
> + *
> + * Return 0 if all went well else appropriate error value.
> + */
> +static int ti_sci_intr_irq_domain_alloc(struct irq_domain *domain,
> +					unsigned int virq, unsigned int nr_irqs,
> +					void *data)
> +{
> +	struct irq_fwspec *fwspec = data;
> +	struct ti_sci_intr_irq_desc *desc;
> +	unsigned long hwirq;
> +	u16 src_id, src_index;
> +	int i, err;
> +	u32 type;
> +
> +	err = ti_sci_intr_irq_domain_translate(domain, fwspec, &hwirq, &type);
> +	if (err)
> +		return err;
> +
> +	src_id = HWIRQ_TO_DEVID(hwirq);
> +	src_index = HWIRQ_TO_IRQID(hwirq);
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		desc = allocate_gic_irq(domain, virq + i, src_id, src_index + i,
> +					type);
> +		if (IS_ERR(desc))
> +			/* ToDO: Clean already allocated IRQs */
> +			return PTR_ERR(desc);

Please address this. But it also worth realising that this code will
never be called with nr_irqs!=1 (that's only for things like PCI
Multi-MSI).

> +
> +		err = irq_domain_set_hwirq_and_chip(domain, virq + i, hwirq + i,
> +						    &ti_sci_intr_irq_chip,
> +						    desc);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct irq_domain_ops ti_sci_intr_irq_domain_ops = {
> +	.alloc		= ti_sci_intr_irq_domain_alloc,
> +	.free		= ti_sci_intr_irq_domain_free,
> +	.translate	= ti_sci_intr_irq_domain_translate,
> +};
> +
> +static int ti_sci_intr_irq_domain_probe(struct platform_device *pdev)
> +{
> +	struct irq_domain *parent_domain, *domain;
> +	struct ti_sci_intr_irq_domain *intr;
> +	struct device_node *parent_node;
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	parent_node = of_irq_find_parent(dev_of_node(dev));
> +	if (!parent_node) {
> +		dev_err(dev, "Failed to get IRQ parent node\n");
> +		return -ENODEV;
> +	}
> +
> +	parent_domain = irq_find_host(parent_node);
> +	if (!parent_domain) {
> +		dev_err(dev, "Failed to find IRQ parent domain\n");
> +		return -ENODEV;
> +	}
> +
> +	intr = devm_kzalloc(dev, sizeof(*intr), GFP_KERNEL);
> +	if (!intr)
> +		return -ENOMEM;
> +
> +	intr->sci = devm_ti_sci_get_by_phandle(dev, "ti,sci");
> +	if (IS_ERR(intr->sci)) {
> +		ret = PTR_ERR(intr->sci);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev, "ti,sci read fail %d\n", ret);
> +		intr->sci = NULL;
> +		return ret;
> +	}
> +
> +	intr->dst_irq = devm_ti_sci_get_of_resource(intr->sci, dev,
> +						    "ti,sci-rm-range-girq");
> +	if (IS_ERR(intr->dst_irq)) {
> +		dev_err(dev, "Destination irq resource allocation failed\n");
> +		return PTR_ERR(intr->dst_irq);
> +	}
> +
> +	ret = of_property_read_u32(dev_of_node(dev), "ti,sci-dst-id",
> +				   (u32 *)&intr->dst_id);
> +	if (ret) {
> +		dev_err(dev, "missing 'ti,sci-dst-id' property\n");
> +		return -EINVAL;
> +	}

Do you expect other drivers to require similar resource request? If
so, It might be worth getting the firmware interface to do that
work. Specially the "give me my SCI" part.

> +
> +	domain = irq_domain_add_hierarchy(parent_domain, 0, 0, dev_of_node(dev),
> +					  &ti_sci_intr_irq_domain_ops, intr);
> +	if (!domain) {
> +		dev_err(dev, "Failed to allocate IRQ domain\n");
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id ti_sci_intr_irq_domain_of_match[] = {
> +	{ .compatible = "ti,sci-intr", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, ti_sci_intr_irq_domain_of_match);
> +
> +static struct platform_driver ti_sci_intr_irq_domain_driver = {
> +	.probe = ti_sci_intr_irq_domain_probe,
> +	.driver = {
> +		.name = "ti-sci-intr",
> +		.of_match_table = ti_sci_intr_irq_domain_of_match,
> +	},
> +};
> +module_platform_driver(ti_sci_intr_irq_domain_driver);
> +
> +MODULE_AUTHOR("Lokesh Vutla <lokeshvutla@...om>");
> +MODULE_DESCRIPTION("K3 Interrupt Router driver over TI SCI protocol");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.19.0
> 

Thanks,

	M.

-- 
Jazz is not dead, it just smell funny.

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