[linux-block.git] / drivers / irqchip / irq-ti-sci-intr.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Texas Instruments' K3 Interrupt Router irqchip driver
 *
 * Copyright (C) 2018-2019 Texas Instruments Incorporated - https://www.ti.com/
 *	Lokesh Vutla <lokeshvutla@ti.com>
 */

#include <linux/err.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/io.h>
#include <linux/irqchip.h>
#include <linux/irqdomain.h>
#include <linux/of_platform.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/soc/ti/ti_sci_protocol.h>

/**
 * struct ti_sci_intr_irq_domain - Structure representing a TISCI based
 *				   Interrupt Router IRQ domain.
 * @sci:	Pointer to TISCI handle
 * @out_irqs:	TISCI resource pointer representing INTR irqs.
 * @dev:	Struct device pointer.
 * @ti_sci_id:	TI-SCI device identifier
 * @type:	Specifies the trigger type supported by this Interrupt Router
 */
struct ti_sci_intr_irq_domain {
	const struct ti_sci_handle *sci;
	struct ti_sci_resource *out_irqs;
	struct device *dev;
	u32 ti_sci_id;
	u32 type;
};

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_set_type		= irq_chip_set_type_parent,
	.irq_retrigger		= irq_chip_retrigger_hierarchy,
	.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)
{
	struct ti_sci_intr_irq_domain *intr = domain->host_data;

	if (fwspec->param_count != 1)
		return -EINVAL;

	*hwirq = fwspec->param[0];
	*type = intr->type;

	return 0;
}

/**
 * ti_sci_intr_xlate_irq() - Translate hwirq to parent's hwirq.
 * @intr:	IRQ domain corresponding to Interrupt Router
 * @irq:	Hardware irq corresponding to the above irq domain
 *
 * Return parent irq number if translation is available else -ENOENT.
 */
static int ti_sci_intr_xlate_irq(struct ti_sci_intr_irq_domain *intr, u32 irq)
{
	struct device_node *np = dev_of_node(intr->dev);
	u32 base, pbase, size, len;
	const __be32 *range;

	range = of_get_property(np, "ti,interrupt-ranges", &len);
	if (!range)
		return irq;

	for (len /= sizeof(*range); len >= 3; len -= 3) {
		base = be32_to_cpu(*range++);
		pbase = be32_to_cpu(*range++);
		size = be32_to_cpu(*range++);

		if (base <= irq && irq < base + size)
			return irq - base + pbase;
	}

	return -ENOENT;
}

/**
 * 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 irq_data *data;
	int out_irq;

	data = irq_domain_get_irq_data(domain, virq);
	out_irq = (uintptr_t)data->chip_data;

	intr->sci->ops.rm_irq_ops.free_irq(intr->sci,
					   intr->ti_sci_id, data->hwirq,
					   intr->ti_sci_id, out_irq);
	ti_sci_release_resource(intr->out_irqs, out_irq);
	irq_domain_free_irqs_parent(domain, virq, 1);
	irq_domain_reset_irq_data(data);
}

/**
 * ti_sci_intr_alloc_parent_irq() - Allocate parent IRQ
 * @domain:	Pointer to the interrupt router IRQ domain
 * @virq:	Corresponding Linux virtual IRQ number
 * @hwirq:	Corresponding hwirq for the IRQ within this IRQ domain
 *
 * Returns intr output irq if all went well else appropriate error pointer.
 */
static int ti_sci_intr_alloc_parent_irq(struct irq_domain *domain,
					unsigned int virq, u32 hwirq)
{
	struct ti_sci_intr_irq_domain *intr = domain->host_data;
	struct device_node *parent_node;
	struct irq_fwspec fwspec;
	int p_hwirq, err = 0;
	u16 out_irq;

	out_irq = ti_sci_get_free_resource(intr->out_irqs);
	if (out_irq == TI_SCI_RESOURCE_NULL)
		return -EINVAL;

	p_hwirq = ti_sci_intr_xlate_irq(intr, out_irq);
	if (p_hwirq < 0)
		goto err_irqs;

	parent_node = of_irq_find_parent(dev_of_node(intr->dev));
	fwspec.fwnode = of_node_to_fwnode(parent_node);

	if (of_device_is_compatible(parent_node, "arm,gic-v3")) {
		/* Parent is GIC */
		fwspec.param_count = 3;
		fwspec.param[0] = 0;	/* SPI */
		fwspec.param[1] = p_hwirq - 32; /* SPI offset */
		fwspec.param[2] = intr->type;
	} else {
		/* Parent is Interrupt Router */
		fwspec.param_count = 1;
		fwspec.param[0] = p_hwirq;
	}

	err = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
	if (err)
		goto err_irqs;

	err = intr->sci->ops.rm_irq_ops.set_irq(intr->sci,
						intr->ti_sci_id, hwirq,
						intr->ti_sci_id, out_irq);
	if (err)
		goto err_msg;

	return out_irq;

err_msg:
	irq_domain_free_irqs_parent(domain, virq, 1);
err_irqs:
	ti_sci_release_resource(intr->out_irqs, out_irq);
	return 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;
	unsigned long hwirq;
	unsigned int flags;
	int err, out_irq;

	err = ti_sci_intr_irq_domain_translate(domain, fwspec, &hwirq, &flags);
	if (err)
		return err;

	out_irq = ti_sci_intr_alloc_parent_irq(domain, virq, hwirq);
	if (out_irq < 0)
		return out_irq;

	irq_domain_set_hwirq_and_chip(domain, virq, hwirq,
				      &ti_sci_intr_irq_chip,
				      (void *)(uintptr_t)out_irq);

	return 0;
}

static const struct irq_domain_ops ti_sci_intr_irq_domain_ops = {
	.free		= ti_sci_intr_irq_domain_free,
	.alloc		= ti_sci_intr_irq_domain_alloc,
	.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);
	of_node_put(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->dev = dev;
	ret = of_property_read_u32(dev_of_node(dev), "ti,intr-trigger-type",
				   &intr->type);
	if (ret) {
		dev_err(dev, "missing ti,intr-trigger-type property\n");
		return -EINVAL;
	}

	intr->sci = devm_ti_sci_get_by_phandle(dev, "ti,sci");
	if (IS_ERR(intr->sci))
		return dev_err_probe(dev, PTR_ERR(intr->sci),
				     "ti,sci read fail\n");

	ret = of_property_read_u32(dev_of_node(dev), "ti,sci-dev-id",
				   &intr->ti_sci_id);
	if (ret) {
		dev_err(dev, "missing 'ti,sci-dev-id' property\n");
		return -EINVAL;
	}

	intr->out_irqs = devm_ti_sci_get_resource(intr->sci, dev,
						  intr->ti_sci_id,
						  TI_SCI_RESASG_SUBTYPE_IR_OUTPUT);
	if (IS_ERR(intr->out_irqs)) {
		dev_err(dev, "Destination irq resource allocation failed\n");
		return PTR_ERR(intr->out_irqs);
	}

	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;
	}

	dev_info(dev, "Interrupt Router %d domain created\n", intr->ti_sci_id);

	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@ticom>");
MODULE_DESCRIPTION("K3 Interrupt Router driver over TI SCI protocol");
Commit	Line	Data
cd844b07 LV	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Texas Instruments' K3 Interrupt Router irqchip driver
	4	*
a6df49f4	5	* Copyright (C) 2018-2019 Texas Instruments Incorporated - https://www.ti.com/
cd844b07 LV	6	* Lokesh Vutla <lokeshvutla@ti.com>
	7	*/
	8
	9	#include <linux/err.h>
	10	#include <linux/module.h>
	11	#include <linux/moduleparam.h>
	12	#include <linux/io.h>
	13	#include <linux/irqchip.h>
	14	#include <linux/irqdomain.h>
	15	#include <linux/of_platform.h>
	16	#include <linux/of_address.h>
	17	#include <linux/of_irq.h>
	18	#include <linux/soc/ti/ti_sci_protocol.h>
	19
cd844b07 LV	20	/**
	21	* struct ti_sci_intr_irq_domain - Structure representing a TISCI based
	22	* Interrupt Router IRQ domain.
	23	* @sci: Pointer to TISCI handle
a5b659bd LV	24	* @out_irqs: TISCI resource pointer representing INTR irqs.
	25	* @dev: Struct device pointer.
	26	* @ti_sci_id: TI-SCI device identifier
cd844b07 LV	27	* @type: Specifies the trigger type supported by this Interrupt Router
	28	*/
	29	struct ti_sci_intr_irq_domain {
	30	const struct ti_sci_handle *sci;
a5b659bd LV	31	struct ti_sci_resource *out_irqs;
	32	struct device *dev;
	33	u32 ti_sci_id;
cd844b07 LV	34	u32 type;
	35	};
	36
	37	static struct irq_chip ti_sci_intr_irq_chip = {
	38	.name = "INTR",
	39	.irq_eoi = irq_chip_eoi_parent,
	40	.irq_mask = irq_chip_mask_parent,
	41	.irq_unmask = irq_chip_unmask_parent,
	42	.irq_set_type = irq_chip_set_type_parent,
	43	.irq_retrigger = irq_chip_retrigger_hierarchy,
	44	.irq_set_affinity = irq_chip_set_affinity_parent,
	45	};
	46
	47	/**
	48	* ti_sci_intr_irq_domain_translate() - Retrieve hwirq and type from
	49	* IRQ firmware specific handler.
	50	* @domain: Pointer to IRQ domain
	51	* @fwspec: Pointer to IRQ specific firmware structure
	52	* @hwirq: IRQ number identified by hardware
	53	* @type: IRQ type
	54	*
	55	* Return 0 if all went ok else appropriate error.
	56	*/
	57	static int ti_sci_intr_irq_domain_translate(struct irq_domain *domain,
	58	struct irq_fwspec *fwspec,
	59	unsigned long *hwirq,
	60	unsigned int *type)
	61	{
	62	struct ti_sci_intr_irq_domain *intr = domain->host_data;
	63
a5b659bd	64	if (fwspec->param_count != 1)
cd844b07 LV	65	return -EINVAL;
cd844b07 LV	66
a5b659bd	67	*hwirq = fwspec->param[0];
cd844b07 LV	68	*type = intr->type;
	69
	70	return 0;
	71	}
	72
a5b659bd LV	73	/**
	74	* ti_sci_intr_xlate_irq() - Translate hwirq to parent's hwirq.
	75	* @intr: IRQ domain corresponding to Interrupt Router
	76	* @irq: Hardware irq corresponding to the above irq domain
	77	*
	78	* Return parent irq number if translation is available else -ENOENT.
	79	*/
	80	static int ti_sci_intr_xlate_irq(struct ti_sci_intr_irq_domain *intr, u32 irq)
	81	{
	82	struct device_node *np = dev_of_node(intr->dev);
	83	u32 base, pbase, size, len;
	84	const __be32 *range;
	85
	86	range = of_get_property(np, "ti,interrupt-ranges", &len);
	87	if (!range)
	88	return irq;
	89
	90	for (len /= sizeof(*range); len >= 3; len -= 3) {
	91	base = be32_to_cpu(*range++);
	92	pbase = be32_to_cpu(*range++);
	93	size = be32_to_cpu(*range++);
	94
	95	if (base <= irq && irq < base + size)
	96	return irq - base + pbase;
	97	}
	98
	99	return -ENOENT;
	100	}
	101
cd844b07 LV	102	/**
	103	* ti_sci_intr_irq_domain_free() - Free the specified IRQs from the domain.
	104	* @domain: Domain to which the irqs belong
	105	* @virq: Linux virtual IRQ to be freed.
	106	* @nr_irqs: Number of continuous irqs to be freed
	107	*/
	108	static void ti_sci_intr_irq_domain_free(struct irq_domain *domain,
	109	unsigned int virq, unsigned int nr_irqs)
	110	{
	111	struct ti_sci_intr_irq_domain *intr = domain->host_data;
a5b659bd LV	112	struct irq_data *data;
a5b659bd LV	113	int out_irq;
cd844b07	114
cd844b07	115	data = irq_domain_get_irq_data(domain, virq);
a5b659bd	116	out_irq = (uintptr_t)data->chip_data;
cd844b07	117
a5b659bd LV	118	intr->sci->ops.rm_irq_ops.free_irq(intr->sci,
	119	intr->ti_sci_id, data->hwirq,
	120	intr->ti_sci_id, out_irq);
	121	ti_sci_release_resource(intr->out_irqs, out_irq);
cd844b07 LV	122	irq_domain_free_irqs_parent(domain, virq, 1);
	123	irq_domain_reset_irq_data(data);
	124	}
	125
	126	/**
a5b659bd	127	* ti_sci_intr_alloc_parent_irq() - Allocate parent IRQ
cd844b07 LV	128	* @domain: Pointer to the interrupt router IRQ domain
	129	* @virq: Corresponding Linux virtual IRQ number
	130	* @hwirq: Corresponding hwirq for the IRQ within this IRQ domain
	131	*
fc6c7cd3	132	* Returns intr output irq if all went well else appropriate error pointer.
cd844b07	133	*/
a5b659bd LV	134	static int ti_sci_intr_alloc_parent_irq(struct irq_domain *domain,
a5b659bd LV	135	unsigned int virq, u32 hwirq)
cd844b07 LV	136	{
cd844b07 LV	137	struct ti_sci_intr_irq_domain *intr = domain->host_data;
a5b659bd	138	struct device_node *parent_node;
cd844b07	139	struct irq_fwspec fwspec;
8ddf1905 Y	140	int p_hwirq, err = 0;
8ddf1905 Y	141	u16 out_irq;
cd844b07	142
a5b659bd LV	143	out_irq = ti_sci_get_free_resource(intr->out_irqs);
a5b659bd LV	144	if (out_irq == TI_SCI_RESOURCE_NULL)
cd844b07 LV	145	return -EINVAL;
cd844b07 LV	146
a5b659bd LV	147	p_hwirq = ti_sci_intr_xlate_irq(intr, out_irq);
	148	if (p_hwirq < 0)
	149	goto err_irqs;
	150
	151	parent_node = of_irq_find_parent(dev_of_node(intr->dev));
	152	fwspec.fwnode = of_node_to_fwnode(parent_node);
	153
	154	if (of_device_is_compatible(parent_node, "arm,gic-v3")) {
	155	/* Parent is GIC */
	156	fwspec.param_count = 3;
	157	fwspec.param[0] = 0; /* SPI */
	158	fwspec.param[1] = p_hwirq - 32; /* SPI offset */
	159	fwspec.param[2] = intr->type;
	160	} else {
	161	/* Parent is Interrupt Router */
	162	fwspec.param_count = 1;
	163	fwspec.param[0] = p_hwirq;
	164	}
cd844b07 LV	165
	166	err = irq_domain_alloc_irqs_parent(domain, virq, 1, &fwspec);
	167	if (err)
	168	goto err_irqs;
	169
a5b659bd LV	170	err = intr->sci->ops.rm_irq_ops.set_irq(intr->sci,
	171	intr->ti_sci_id, hwirq,
	172	intr->ti_sci_id, out_irq);
cd844b07 LV	173	if (err)
	174	goto err_msg;
	175
fc6c7cd3	176	return out_irq;
cd844b07 LV	177
	178	err_msg:
	179	irq_domain_free_irqs_parent(domain, virq, 1);
	180	err_irqs:
a5b659bd	181	ti_sci_release_resource(intr->out_irqs, out_irq);
cd844b07 LV	182	return err;
	183	}
	184
	185	/**
	186	* ti_sci_intr_irq_domain_alloc() - Allocate Interrupt router IRQs
	187	* @domain: Point to the interrupt router IRQ domain
	188	* @virq: Corresponding Linux virtual IRQ number
	189	* @nr_irqs: Continuous irqs to be allocated
	190	* @data: Pointer to firmware specifier
	191	*
	192	* Return 0 if all went well else appropriate error value.
	193	*/
	194	static int ti_sci_intr_irq_domain_alloc(struct irq_domain *domain,
	195	unsigned int virq, unsigned int nr_irqs,
	196	void *data)
	197	{
	198	struct irq_fwspec *fwspec = data;
	199	unsigned long hwirq;
	200	unsigned int flags;
fc6c7cd3	201	int err, out_irq;
cd844b07 LV	202
	203	err = ti_sci_intr_irq_domain_translate(domain, fwspec, &hwirq, &flags);
	204	if (err)
	205	return err;
	206
fc6c7cd3 LV	207	out_irq = ti_sci_intr_alloc_parent_irq(domain, virq, hwirq);
	208	if (out_irq < 0)
	209	return out_irq;
cd844b07 LV	210
cd844b07 LV	211	irq_domain_set_hwirq_and_chip(domain, virq, hwirq,
a5b659bd	212	&ti_sci_intr_irq_chip,
fc6c7cd3	213	(void *)(uintptr_t)out_irq);
cd844b07 LV	214
	215	return 0;
	216	}
	217
	218	static const struct irq_domain_ops ti_sci_intr_irq_domain_ops = {
	219	.free = ti_sci_intr_irq_domain_free,
	220	.alloc = ti_sci_intr_irq_domain_alloc,
	221	.translate = ti_sci_intr_irq_domain_translate,
	222	};
	223
	224	static int ti_sci_intr_irq_domain_probe(struct platform_device *pdev)
	225	{
	226	struct irq_domain parent_domain, domain;
	227	struct ti_sci_intr_irq_domain *intr;
	228	struct device_node *parent_node;
	229	struct device *dev = &pdev->dev;
	230	int ret;
	231
	232	parent_node = of_irq_find_parent(dev_of_node(dev));
	233	if (!parent_node) {
	234	dev_err(dev, "Failed to get IRQ parent node\n");
	235	return -ENODEV;
	236	}
	237
	238	parent_domain = irq_find_host(parent_node);
02298b7b	239	of_node_put(parent_node);
cd844b07 LV	240	if (!parent_domain) {
	241	dev_err(dev, "Failed to find IRQ parent domain\n");
	242	return -ENODEV;
	243	}
	244
	245	intr = devm_kzalloc(dev, sizeof(*intr), GFP_KERNEL);
	246	if (!intr)
	247	return -ENOMEM;
	248
a5b659bd	249	intr->dev = dev;
cd844b07 LV	250	ret = of_property_read_u32(dev_of_node(dev), "ti,intr-trigger-type",
	251	&intr->type);
	252	if (ret) {
	253	dev_err(dev, "missing ti,intr-trigger-type property\n");
	254	return -EINVAL;
	255	}
	256
	257	intr->sci = devm_ti_sci_get_by_phandle(dev, "ti,sci");
ea6c25e6 KK	258	if (IS_ERR(intr->sci))
	259	return dev_err_probe(dev, PTR_ERR(intr->sci),
	260	"ti,sci read fail\n");
cd844b07	261
a5b659bd LV	262	ret = of_property_read_u32(dev_of_node(dev), "ti,sci-dev-id",
a5b659bd LV	263	&intr->ti_sci_id);
cd844b07	264	if (ret) {
a5b659bd	265	dev_err(dev, "missing 'ti,sci-dev-id' property\n");
cd844b07 LV	266	return -EINVAL;
	267	}
	268
a5b659bd LV	269	intr->out_irqs = devm_ti_sci_get_resource(intr->sci, dev,
	270	intr->ti_sci_id,
	271	TI_SCI_RESASG_SUBTYPE_IR_OUTPUT);
	272	if (IS_ERR(intr->out_irqs)) {
cd844b07	273	dev_err(dev, "Destination irq resource allocation failed\n");
a5b659bd	274	return PTR_ERR(intr->out_irqs);
cd844b07 LV	275	}
	276
	277	domain = irq_domain_add_hierarchy(parent_domain, 0, 0, dev_of_node(dev),
	278	&ti_sci_intr_irq_domain_ops, intr);
	279	if (!domain) {
	280	dev_err(dev, "Failed to allocate IRQ domain\n");
	281	return -ENOMEM;
	282	}
	283
a5b659bd LV	284	dev_info(dev, "Interrupt Router %d domain created\n", intr->ti_sci_id);
a5b659bd LV	285
cd844b07 LV	286	return 0;
	287	}
	288
	289	static const struct of_device_id ti_sci_intr_irq_domain_of_match[] = {
	290	{ .compatible = "ti,sci-intr", },
	291	{ /* sentinel */ },
	292	};
	293	MODULE_DEVICE_TABLE(of, ti_sci_intr_irq_domain_of_match);
	294
	295	static struct platform_driver ti_sci_intr_irq_domain_driver = {
	296	.probe = ti_sci_intr_irq_domain_probe,
	297	.driver = {
	298	.name = "ti-sci-intr",
	299	.of_match_table = ti_sci_intr_irq_domain_of_match,
	300	},
	301	};
	302	module_platform_driver(ti_sci_intr_irq_domain_driver);
	303
	304	MODULE_AUTHOR("Lokesh Vutla <lokeshvutla@ticom>");
	305	MODULE_DESCRIPTION("K3 Interrupt Router driver over TI SCI protocol");