1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Surface Book (2 and later) hot-plug driver.
4 *
5 * Surface Book devices (can) have a hot-pluggable discrete GPU (dGPU). This
6 * driver is responsible for out-of-band hot-plug event signaling on these
7 * devices. It is specifically required when the hot-plug device is in D3cold
8 * and can thus not generate PCIe hot-plug events itself.
9 *
10 * Event signaling is handled via ACPI, which will generate the appropriate
11 * device-check notifications to be picked up by the PCIe hot-plug driver.
12 *
13 * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
14 */
15
16#include <linux/acpi.h>
17#include <linux/gpio.h>
18#include <linux/interrupt.h>
19#include <linux/kernel.h>
20#include <linux/module.h>
21#include <linux/mutex.h>
22#include <linux/platform_device.h>
23
24static const struct acpi_gpio_params shps_base_presence_int   = { 0, 0, false };
25static const struct acpi_gpio_params shps_base_presence       = { 1, 0, false };
26static const struct acpi_gpio_params shps_device_power_int    = { 2, 0, false };
27static const struct acpi_gpio_params shps_device_power        = { 3, 0, false };
28static const struct acpi_gpio_params shps_device_presence_int = { 4, 0, false };
29static const struct acpi_gpio_params shps_device_presence     = { 5, 0, false };
30
31static const struct acpi_gpio_mapping shps_acpi_gpios[] = {
32	{ "base_presence-int-gpio",   &shps_base_presence_int,   1 },
33	{ "base_presence-gpio",       &shps_base_presence,       1 },
34	{ "device_power-int-gpio",    &shps_device_power_int,    1 },
35	{ "device_power-gpio",        &shps_device_power,        1 },
36	{ "device_presence-int-gpio", &shps_device_presence_int, 1 },
37	{ "device_presence-gpio",     &shps_device_presence,     1 },
38	{ },
39};
40
41/* 5515a847-ed55-4b27-8352-cd320e10360a */
42static const guid_t shps_dsm_guid =
43	GUID_INIT(0x5515a847, 0xed55, 0x4b27, 0x83, 0x52, 0xcd, 0x32, 0x0e, 0x10, 0x36, 0x0a);
44
45#define SHPS_DSM_REVISION		1
46
47enum shps_dsm_fn {
48	SHPS_DSM_FN_PCI_NUM_ENTRIES	= 0x01,
49	SHPS_DSM_FN_PCI_GET_ENTRIES	= 0x02,
50	SHPS_DSM_FN_IRQ_BASE_PRESENCE	= 0x03,
51	SHPS_DSM_FN_IRQ_DEVICE_POWER	= 0x04,
52	SHPS_DSM_FN_IRQ_DEVICE_PRESENCE	= 0x05,
53};
54
55enum shps_irq_type {
56	/* NOTE: Must be in order of enum shps_dsm_fn above. */
57	SHPS_IRQ_TYPE_BASE_PRESENCE	= 0,
58	SHPS_IRQ_TYPE_DEVICE_POWER	= 1,
59	SHPS_IRQ_TYPE_DEVICE_PRESENCE	= 2,
60	SHPS_NUM_IRQS,
61};
62
63static const char *const shps_gpio_names[] = {
64	[SHPS_IRQ_TYPE_BASE_PRESENCE]	= "base_presence",
65	[SHPS_IRQ_TYPE_DEVICE_POWER]	= "device_power",
66	[SHPS_IRQ_TYPE_DEVICE_PRESENCE]	= "device_presence",
67};
68
69struct shps_device {
70	struct mutex lock[SHPS_NUM_IRQS];  /* Protects update in shps_dsm_notify_irq() */
71	struct gpio_desc *gpio[SHPS_NUM_IRQS];
72	unsigned int irq[SHPS_NUM_IRQS];
73};
74
75#define SHPS_IRQ_NOT_PRESENT		((unsigned int)-1)
76
77static enum shps_dsm_fn shps_dsm_fn_for_irq(enum shps_irq_type type)
78{
79	return SHPS_DSM_FN_IRQ_BASE_PRESENCE + type;
80}
81
82static void shps_dsm_notify_irq(struct platform_device *pdev, enum shps_irq_type type)
83{
84	struct shps_device *sdev = platform_get_drvdata(pdev);
85	acpi_handle handle = ACPI_HANDLE(&pdev->dev);
86	union acpi_object *result;
87	union acpi_object param;
88	int value;
89
90	mutex_lock(&sdev->lock[type]);
91
92	value = gpiod_get_value_cansleep(sdev->gpio[type]);
93	if (value < 0) {
94		mutex_unlock(&sdev->lock[type]);
95		dev_err(&pdev->dev, "failed to get gpio: %d (irq=%d)\n", type, value);
96		return;
97	}
98
99	dev_dbg(&pdev->dev, "IRQ notification via DSM (irq=%d, value=%d)\n", type, value);
100
101	param.type = ACPI_TYPE_INTEGER;
102	param.integer.value = value;
103
104	result = acpi_evaluate_dsm_typed(handle, &shps_dsm_guid, SHPS_DSM_REVISION,
105					 shps_dsm_fn_for_irq(type), &param, ACPI_TYPE_BUFFER);
106	if (!result) {
107		dev_err(&pdev->dev, "IRQ notification via DSM failed (irq=%d, gpio=%d)\n",
108			type, value);
109
110	} else if (result->buffer.length != 1 || result->buffer.pointer[0] != 0) {
111		dev_err(&pdev->dev,
112			"IRQ notification via DSM failed: unexpected result value (irq=%d, gpio=%d)\n",
113			type, value);
114	}
115
116	mutex_unlock(&sdev->lock[type]);
117
118	ACPI_FREE(result);
119}
120
121static irqreturn_t shps_handle_irq(int irq, void *data)
122{
123	struct platform_device *pdev = data;
124	struct shps_device *sdev = platform_get_drvdata(pdev);
125	int type;
126
127	/* Figure out which IRQ we're handling. */
128	for (type = 0; type < SHPS_NUM_IRQS; type++)
129		if (irq == sdev->irq[type])
130			break;
131
132	/* We should have found our interrupt, if not: this is a bug. */
133	if (WARN(type >= SHPS_NUM_IRQS, "invalid IRQ number: %d\n", irq))
134		return IRQ_HANDLED;
135
136	/* Forward interrupt to ACPI via DSM. */
137	shps_dsm_notify_irq(pdev, type);
138	return IRQ_HANDLED;
139}
140
141static int shps_setup_irq(struct platform_device *pdev, enum shps_irq_type type)
142{
143	unsigned long flags = IRQF_ONESHOT | IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
144	struct shps_device *sdev = platform_get_drvdata(pdev);
145	struct gpio_desc *gpiod;
146	acpi_handle handle = ACPI_HANDLE(&pdev->dev);
147	const char *irq_name;
148	const int dsm = shps_dsm_fn_for_irq(type);
149	int status, irq;
150
151	/*
152	 * Only set up interrupts that we actually need: The Surface Book 3
153	 * does not have a DSM for base presence, so don't set up an interrupt
154	 * for that.
155	 */
156	if (!acpi_check_dsm(handle, &shps_dsm_guid, SHPS_DSM_REVISION, BIT(dsm))) {
157		dev_dbg(&pdev->dev, "IRQ notification via DSM not present (irq=%d)\n", type);
158		return 0;
159	}
160
161	gpiod = devm_gpiod_get(&pdev->dev, shps_gpio_names[type], GPIOD_ASIS);
162	if (IS_ERR(gpiod))
163		return PTR_ERR(gpiod);
164
165	irq = gpiod_to_irq(gpiod);
166	if (irq < 0)
167		return irq;
168
169	irq_name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "shps-irq-%d", type);
170	if (!irq_name)
171		return -ENOMEM;
172
173	status = devm_request_threaded_irq(&pdev->dev, irq, NULL, shps_handle_irq,
174					   flags, irq_name, pdev);
175	if (status)
176		return status;
177
178	dev_dbg(&pdev->dev, "set up irq %d as type %d\n", irq, type);
179
180	sdev->gpio[type] = gpiod;
181	sdev->irq[type] = irq;
182
183	return 0;
184}
185
186static void surface_hotplug_remove(struct platform_device *pdev)
187{
188	struct shps_device *sdev = platform_get_drvdata(pdev);
189	int i;
190
191	/* Ensure that IRQs have been fully handled and won't trigger any more. */
192	for (i = 0; i < SHPS_NUM_IRQS; i++) {
193		if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
194			disable_irq(sdev->irq[i]);
195
196		mutex_destroy(&sdev->lock[i]);
197	}
198}
199
200static int surface_hotplug_probe(struct platform_device *pdev)
201{
202	struct shps_device *sdev;
203	int status, i;
204
205	/*
206	 * The MSHW0153 device is also present on the Surface Laptop 3,
207	 * however that doesn't have a hot-pluggable PCIe device. It also
208	 * doesn't have any GPIO interrupts/pins under the MSHW0153, so filter
209	 * it out here.
210	 */
211	if (gpiod_count(&pdev->dev, NULL) < 0)
212		return -ENODEV;
213
214	status = devm_acpi_dev_add_driver_gpios(&pdev->dev, shps_acpi_gpios);
215	if (status)
216		return status;
217
218	sdev = devm_kzalloc(&pdev->dev, sizeof(*sdev), GFP_KERNEL);
219	if (!sdev)
220		return -ENOMEM;
221
222	platform_set_drvdata(pdev, sdev);
223
224	/*
225	 * Initialize IRQs so that we can safely call surface_hotplug_remove()
226	 * on errors.
227	 */
228	for (i = 0; i < SHPS_NUM_IRQS; i++)
229		sdev->irq[i] = SHPS_IRQ_NOT_PRESENT;
230
231	/* Set up IRQs. */
232	for (i = 0; i < SHPS_NUM_IRQS; i++) {
233		mutex_init(&sdev->lock[i]);
234
235		status = shps_setup_irq(pdev, i);
236		if (status) {
237			dev_err(&pdev->dev, "failed to set up IRQ %d: %d\n", i, status);
238			goto err;
239		}
240	}
241
242	/* Ensure everything is up-to-date. */
243	for (i = 0; i < SHPS_NUM_IRQS; i++)
244		if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
245			shps_dsm_notify_irq(pdev, i);
246
247	return 0;
248
249err:
250	surface_hotplug_remove(pdev);
251	return status;
252}
253
254static const struct acpi_device_id surface_hotplug_acpi_match[] = {
255	{ "MSHW0153", 0 },
256	{ },
257};
258MODULE_DEVICE_TABLE(acpi, surface_hotplug_acpi_match);
259
260static struct platform_driver surface_hotplug_driver = {
261	.probe = surface_hotplug_probe,
262	.remove_new = surface_hotplug_remove,
263	.driver = {
264		.name = "surface_hotplug",
265		.acpi_match_table = surface_hotplug_acpi_match,
266		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
267	},
268};
269module_platform_driver(surface_hotplug_driver);
270
271MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
272MODULE_DESCRIPTION("Surface Hot-Plug Signaling Driver for Surface Book Devices");
273MODULE_LICENSE("GPL");
274