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 
24 static const struct acpi_gpio_params shps_base_presence_int   = { 0, 0, false };
25 static const struct acpi_gpio_params shps_base_presence       = { 1, 0, false };
26 static const struct acpi_gpio_params shps_device_power_int    = { 2, 0, false };
27 static const struct acpi_gpio_params shps_device_power        = { 3, 0, false };
28 static const struct acpi_gpio_params shps_device_presence_int = { 4, 0, false };
29 static const struct acpi_gpio_params shps_device_presence     = { 5, 0, false };
30 
31 static 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 */
42 static 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 
47 enum 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 
55 enum 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 
63 static 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 
69 struct 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 
77 static 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 
82 static 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(handle, &shps_dsm_guid, SHPS_DSM_REVISION,
105 				   shps_dsm_fn_for_irq(type), &param);
106 
107 	if (!result) {
108 		dev_err(&pdev->dev, "IRQ notification via DSM failed (irq=%d, gpio=%d)\n",
109 			type, value);
110 
111 	} else if (result->type != ACPI_TYPE_BUFFER) {
112 		dev_err(&pdev->dev,
113 			"IRQ notification via DSM failed: unexpected result type (irq=%d, gpio=%d)\n",
114 			type, value);
115 
116 	} else if (result->buffer.length != 1 || result->buffer.pointer[0] != 0) {
117 		dev_err(&pdev->dev,
118 			"IRQ notification via DSM failed: unexpected result value (irq=%d, gpio=%d)\n",
119 			type, value);
120 	}
121 
122 	mutex_unlock(&sdev->lock[type]);
123 
124 	if (result)
125 		ACPI_FREE(result);
126 }
127 
128 static irqreturn_t shps_handle_irq(int irq, void *data)
129 {
130 	struct platform_device *pdev = data;
131 	struct shps_device *sdev = platform_get_drvdata(pdev);
132 	int type;
133 
134 	/* Figure out which IRQ we're handling. */
135 	for (type = 0; type < SHPS_NUM_IRQS; type++)
136 		if (irq == sdev->irq[type])
137 			break;
138 
139 	/* We should have found our interrupt, if not: this is a bug. */
140 	if (WARN(type >= SHPS_NUM_IRQS, "invalid IRQ number: %d\n", irq))
141 		return IRQ_HANDLED;
142 
143 	/* Forward interrupt to ACPI via DSM. */
144 	shps_dsm_notify_irq(pdev, type);
145 	return IRQ_HANDLED;
146 }
147 
148 static int shps_setup_irq(struct platform_device *pdev, enum shps_irq_type type)
149 {
150 	unsigned long flags = IRQF_ONESHOT | IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
151 	struct shps_device *sdev = platform_get_drvdata(pdev);
152 	struct gpio_desc *gpiod;
153 	acpi_handle handle = ACPI_HANDLE(&pdev->dev);
154 	const char *irq_name;
155 	const int dsm = shps_dsm_fn_for_irq(type);
156 	int status, irq;
157 
158 	/*
159 	 * Only set up interrupts that we actually need: The Surface Book 3
160 	 * does not have a DSM for base presence, so don't set up an interrupt
161 	 * for that.
162 	 */
163 	if (!acpi_check_dsm(handle, &shps_dsm_guid, SHPS_DSM_REVISION, BIT(dsm))) {
164 		dev_dbg(&pdev->dev, "IRQ notification via DSM not present (irq=%d)\n", type);
165 		return 0;
166 	}
167 
168 	gpiod = devm_gpiod_get(&pdev->dev, shps_gpio_names[type], GPIOD_ASIS);
169 	if (IS_ERR(gpiod))
170 		return PTR_ERR(gpiod);
171 
172 	irq = gpiod_to_irq(gpiod);
173 	if (irq < 0)
174 		return irq;
175 
176 	irq_name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "shps-irq-%d", type);
177 	if (!irq_name)
178 		return -ENOMEM;
179 
180 	status = devm_request_threaded_irq(&pdev->dev, irq, NULL, shps_handle_irq,
181 					   flags, irq_name, pdev);
182 	if (status)
183 		return status;
184 
185 	dev_dbg(&pdev->dev, "set up irq %d as type %d\n", irq, type);
186 
187 	sdev->gpio[type] = gpiod;
188 	sdev->irq[type] = irq;
189 
190 	return 0;
191 }
192 
193 static int surface_hotplug_remove(struct platform_device *pdev)
194 {
195 	struct shps_device *sdev = platform_get_drvdata(pdev);
196 	int i;
197 
198 	/* Ensure that IRQs have been fully handled and won't trigger any more. */
199 	for (i = 0; i < SHPS_NUM_IRQS; i++) {
200 		if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
201 			disable_irq(sdev->irq[i]);
202 
203 		mutex_destroy(&sdev->lock[i]);
204 	}
205 
206 	return 0;
207 }
208 
209 static int surface_hotplug_probe(struct platform_device *pdev)
210 {
211 	struct shps_device *sdev;
212 	int status, i;
213 
214 	/*
215 	 * The MSHW0153 device is also present on the Surface Laptop 3,
216 	 * however that doesn't have a hot-pluggable PCIe device. It also
217 	 * doesn't have any GPIO interrupts/pins under the MSHW0153, so filter
218 	 * it out here.
219 	 */
220 	if (gpiod_count(&pdev->dev, NULL) < 0)
221 		return -ENODEV;
222 
223 	status = devm_acpi_dev_add_driver_gpios(&pdev->dev, shps_acpi_gpios);
224 	if (status)
225 		return status;
226 
227 	sdev = devm_kzalloc(&pdev->dev, sizeof(*sdev), GFP_KERNEL);
228 	if (!sdev)
229 		return -ENOMEM;
230 
231 	platform_set_drvdata(pdev, sdev);
232 
233 	/*
234 	 * Initialize IRQs so that we can safely call surface_hotplug_remove()
235 	 * on errors.
236 	 */
237 	for (i = 0; i < SHPS_NUM_IRQS; i++)
238 		sdev->irq[i] = SHPS_IRQ_NOT_PRESENT;
239 
240 	/* Set up IRQs. */
241 	for (i = 0; i < SHPS_NUM_IRQS; i++) {
242 		mutex_init(&sdev->lock[i]);
243 
244 		status = shps_setup_irq(pdev, i);
245 		if (status) {
246 			dev_err(&pdev->dev, "failed to set up IRQ %d: %d\n", i, status);
247 			goto err;
248 		}
249 	}
250 
251 	/* Ensure everything is up-to-date. */
252 	for (i = 0; i < SHPS_NUM_IRQS; i++)
253 		if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
254 			shps_dsm_notify_irq(pdev, i);
255 
256 	return 0;
257 
258 err:
259 	surface_hotplug_remove(pdev);
260 	return status;
261 }
262 
263 static const struct acpi_device_id surface_hotplug_acpi_match[] = {
264 	{ "MSHW0153", 0 },
265 	{ },
266 };
267 MODULE_DEVICE_TABLE(acpi, surface_hotplug_acpi_match);
268 
269 static struct platform_driver surface_hotplug_driver = {
270 	.probe = surface_hotplug_probe,
271 	.remove = surface_hotplug_remove,
272 	.driver = {
273 		.name = "surface_hotplug",
274 		.acpi_match_table = surface_hotplug_acpi_match,
275 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
276 	},
277 };
278 module_platform_driver(surface_hotplug_driver);
279 
280 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
281 MODULE_DESCRIPTION("Surface Hot-Plug Signaling Driver for Surface Book Devices");
282 MODULE_LICENSE("GPL");
283