1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright 2019 Google Inc
4  *
5  * This program is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU General Public License
7  * as published by the Free Software Foundation; either version
8  * 2 of the License, or (at your option) any later version.
9  *
10  * Provides a simple driver to control the ASPEED P2A interface which allows
11  * the host to read and write to various regions of the BMC's memory.
12  */
13 
14 #include <linux/fs.h>
15 #include <linux/io.h>
16 #include <linux/mfd/syscon.h>
17 #include <linux/miscdevice.h>
18 #include <linux/mm.h>
19 #include <linux/module.h>
20 #include <linux/mutex.h>
21 #include <linux/of_address.h>
22 #include <linux/of_device.h>
23 #include <linux/platform_device.h>
24 #include <linux/regmap.h>
25 #include <linux/slab.h>
26 #include <linux/uaccess.h>
27 
28 #include <linux/aspeed-p2a-ctrl.h>
29 
30 #define DEVICE_NAME	"aspeed-p2a-ctrl"
31 
32 /* SCU2C is a Misc. Control Register. */
33 #define SCU2C 0x2c
34 /* SCU180 is the PCIe Configuration Setting Control Register. */
35 #define SCU180 0x180
36 /* Bit 1 controls the P2A bridge, while bit 0 controls the entire VGA device
37  * on the PCI bus.
38  */
39 #define SCU180_ENP2A BIT(1)
40 
41 /* The ast2400/2500 both have six ranges. */
42 #define P2A_REGION_COUNT 6
43 
44 struct region {
45 	u64 min;
46 	u64 max;
47 	u32 bit;
48 };
49 
50 struct aspeed_p2a_model_data {
51 	/* min, max, bit */
52 	struct region regions[P2A_REGION_COUNT];
53 };
54 
55 struct aspeed_p2a_ctrl {
56 	struct miscdevice miscdev;
57 	struct regmap *regmap;
58 
59 	const struct aspeed_p2a_model_data *config;
60 
61 	/* Access to these needs to be locked, held via probe, mapping ioctl,
62 	 * and release, remove.
63 	 */
64 	struct mutex tracking;
65 	u32 readers;
66 	u32 readerwriters[P2A_REGION_COUNT];
67 
68 	phys_addr_t mem_base;
69 	resource_size_t mem_size;
70 };
71 
72 struct aspeed_p2a_user {
73 	struct file *file;
74 	struct aspeed_p2a_ctrl *parent;
75 
76 	/* The entire memory space is opened for reading once the bridge is
77 	 * enabled, therefore this needs only to be tracked once per user.
78 	 * If any user has it open for read, the bridge must stay enabled.
79 	 */
80 	u32 read;
81 
82 	/* Each entry of the array corresponds to a P2A Region.  If the user
83 	 * opens for read or readwrite, the reference goes up here.  On
84 	 * release, this array is walked and references adjusted accordingly.
85 	 */
86 	u32 readwrite[P2A_REGION_COUNT];
87 };
88 
89 static void aspeed_p2a_enable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
90 {
91 	regmap_update_bits(p2a_ctrl->regmap,
92 		SCU180, SCU180_ENP2A, SCU180_ENP2A);
93 }
94 
95 static void aspeed_p2a_disable_bridge(struct aspeed_p2a_ctrl *p2a_ctrl)
96 {
97 	regmap_update_bits(p2a_ctrl->regmap, SCU180, SCU180_ENP2A, 0);
98 }
99 
100 static int aspeed_p2a_mmap(struct file *file, struct vm_area_struct *vma)
101 {
102 	unsigned long vsize;
103 	pgprot_t prot;
104 	struct aspeed_p2a_user *priv = file->private_data;
105 	struct aspeed_p2a_ctrl *ctrl = priv->parent;
106 
107 	if (ctrl->mem_base == 0 && ctrl->mem_size == 0)
108 		return -EINVAL;
109 
110 	vsize = vma->vm_end - vma->vm_start;
111 	prot = vma->vm_page_prot;
112 
113 	if (vma->vm_pgoff + vsize > ctrl->mem_base + ctrl->mem_size)
114 		return -EINVAL;
115 
116 	/* ast2400/2500 AHB accesses are not cache coherent */
117 	prot = pgprot_noncached(prot);
118 
119 	if (remap_pfn_range(vma, vma->vm_start,
120 		(ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
121 		vsize, prot))
122 		return -EAGAIN;
123 
124 	return 0;
125 }
126 
127 static bool aspeed_p2a_region_acquire(struct aspeed_p2a_user *priv,
128 		struct aspeed_p2a_ctrl *ctrl,
129 		struct aspeed_p2a_ctrl_mapping *map)
130 {
131 	int i;
132 	u64 base, end;
133 	bool matched = false;
134 
135 	base = map->addr;
136 	end = map->addr + (map->length - 1);
137 
138 	/* If the value is a legal u32, it will find a match. */
139 	for (i = 0; i < P2A_REGION_COUNT; i++) {
140 		const struct region *curr = &ctrl->config->regions[i];
141 
142 		/* If the top of this region is lower than your base, skip it.
143 		 */
144 		if (curr->max < base)
145 			continue;
146 
147 		/* If the bottom of this region is higher than your end, bail.
148 		 */
149 		if (curr->min > end)
150 			break;
151 
152 		/* Lock this and update it, therefore it someone else is
153 		 * closing their file out, this'll preserve the increment.
154 		 */
155 		mutex_lock(&ctrl->tracking);
156 		ctrl->readerwriters[i] += 1;
157 		mutex_unlock(&ctrl->tracking);
158 
159 		/* Track with the user, so when they close their file, we can
160 		 * decrement properly.
161 		 */
162 		priv->readwrite[i] += 1;
163 
164 		/* Enable the region as read-write. */
165 		regmap_update_bits(ctrl->regmap, SCU2C, curr->bit, 0);
166 		matched = true;
167 	}
168 
169 	return matched;
170 }
171 
172 static long aspeed_p2a_ioctl(struct file *file, unsigned int cmd,
173 		unsigned long data)
174 {
175 	struct aspeed_p2a_user *priv = file->private_data;
176 	struct aspeed_p2a_ctrl *ctrl = priv->parent;
177 	void __user *arg = (void __user *)data;
178 	struct aspeed_p2a_ctrl_mapping map;
179 
180 	if (copy_from_user(&map, arg, sizeof(map)))
181 		return -EFAULT;
182 
183 	switch (cmd) {
184 	case ASPEED_P2A_CTRL_IOCTL_SET_WINDOW:
185 		/* If they want a region to be read-only, since the entire
186 		 * region is read-only once enabled, we just need to track this
187 		 * user wants to read from the bridge, and if it's not enabled.
188 		 * Enable it.
189 		 */
190 		if (map.flags == ASPEED_P2A_CTRL_READ_ONLY) {
191 			mutex_lock(&ctrl->tracking);
192 			ctrl->readers += 1;
193 			mutex_unlock(&ctrl->tracking);
194 
195 			/* Track with the user, so when they close their file,
196 			 * we can decrement properly.
197 			 */
198 			priv->read += 1;
199 		} else if (map.flags == ASPEED_P2A_CTRL_READWRITE) {
200 			/* If we don't acquire any region return error. */
201 			if (!aspeed_p2a_region_acquire(priv, ctrl, &map)) {
202 				return -EINVAL;
203 			}
204 		} else {
205 			/* Invalid map flags. */
206 			return -EINVAL;
207 		}
208 
209 		aspeed_p2a_enable_bridge(ctrl);
210 		return 0;
211 	case ASPEED_P2A_CTRL_IOCTL_GET_MEMORY_CONFIG:
212 		/* This is a request for the memory-region and corresponding
213 		 * length that is used by the driver for mmap.
214 		 */
215 
216 		map.flags = 0;
217 		map.addr = ctrl->mem_base;
218 		map.length = ctrl->mem_size;
219 
220 		return copy_to_user(arg, &map, sizeof(map)) ? -EFAULT : 0;
221 	}
222 
223 	return -EINVAL;
224 }
225 
226 
227 /*
228  * When a user opens this file, we create a structure to track their mappings.
229  *
230  * A user can map a region as read-only (bridge enabled), or read-write (bit
231  * flipped, and bridge enabled).  Either way, this tracking is used, s.t. when
232  * they release the device references are handled.
233  *
234  * The bridge is not enabled until a user calls an ioctl to map a region,
235  * simply opening the device does not enable it.
236  */
237 static int aspeed_p2a_open(struct inode *inode, struct file *file)
238 {
239 	struct aspeed_p2a_user *priv;
240 
241 	priv = kmalloc(sizeof(*priv), GFP_KERNEL);
242 	if (!priv)
243 		return -ENOMEM;
244 
245 	priv->file = file;
246 	priv->read = 0;
247 	memset(priv->readwrite, 0, sizeof(priv->readwrite));
248 
249 	/* The file's private_data is initialized to the p2a_ctrl. */
250 	priv->parent = file->private_data;
251 
252 	/* Set the file's private_data to the user's data. */
253 	file->private_data = priv;
254 
255 	return 0;
256 }
257 
258 /*
259  * This will close the users mappings.  It will go through what they had opened
260  * for readwrite, and decrement those counts.  If at the end, this is the last
261  * user, it'll close the bridge.
262  */
263 static int aspeed_p2a_release(struct inode *inode, struct file *file)
264 {
265 	int i;
266 	u32 bits = 0;
267 	bool open_regions = false;
268 	struct aspeed_p2a_user *priv = file->private_data;
269 
270 	/* Lock others from changing these values until everything is updated
271 	 * in one pass.
272 	 */
273 	mutex_lock(&priv->parent->tracking);
274 
275 	priv->parent->readers -= priv->read;
276 
277 	for (i = 0; i < P2A_REGION_COUNT; i++) {
278 		priv->parent->readerwriters[i] -= priv->readwrite[i];
279 
280 		if (priv->parent->readerwriters[i] > 0)
281 			open_regions = true;
282 		else
283 			bits |= priv->parent->config->regions[i].bit;
284 	}
285 
286 	/* Setting a bit to 1 disables the region, so let's just OR with the
287 	 * above to disable any.
288 	 */
289 
290 	/* Note, if another user is trying to ioctl, they can't grab tracking,
291 	 * and therefore can't grab either register mutex.
292 	 * If another user is trying to close, they can't grab tracking either.
293 	 */
294 	regmap_update_bits(priv->parent->regmap, SCU2C, bits, bits);
295 
296 	/* If parent->readers is zero and open windows is 0, disable the
297 	 * bridge.
298 	 */
299 	if (!open_regions && priv->parent->readers == 0)
300 		aspeed_p2a_disable_bridge(priv->parent);
301 
302 	mutex_unlock(&priv->parent->tracking);
303 
304 	kfree(priv);
305 
306 	return 0;
307 }
308 
309 static const struct file_operations aspeed_p2a_ctrl_fops = {
310 	.owner = THIS_MODULE,
311 	.mmap = aspeed_p2a_mmap,
312 	.unlocked_ioctl = aspeed_p2a_ioctl,
313 	.open = aspeed_p2a_open,
314 	.release = aspeed_p2a_release,
315 };
316 
317 /* The regions are controlled by SCU2C */
318 static void aspeed_p2a_disable_all(struct aspeed_p2a_ctrl *p2a_ctrl)
319 {
320 	int i;
321 	u32 value = 0;
322 
323 	for (i = 0; i < P2A_REGION_COUNT; i++)
324 		value |= p2a_ctrl->config->regions[i].bit;
325 
326 	regmap_update_bits(p2a_ctrl->regmap, SCU2C, value, value);
327 
328 	/* Disable the bridge. */
329 	aspeed_p2a_disable_bridge(p2a_ctrl);
330 }
331 
332 static int aspeed_p2a_ctrl_probe(struct platform_device *pdev)
333 {
334 	struct aspeed_p2a_ctrl *misc_ctrl;
335 	struct device *dev;
336 	struct resource resm;
337 	struct device_node *node;
338 	int rc = 0;
339 
340 	dev = &pdev->dev;
341 
342 	misc_ctrl = devm_kzalloc(dev, sizeof(*misc_ctrl), GFP_KERNEL);
343 	if (!misc_ctrl)
344 		return -ENOMEM;
345 
346 	mutex_init(&misc_ctrl->tracking);
347 
348 	/* optional. */
349 	node = of_parse_phandle(dev->of_node, "memory-region", 0);
350 	if (node) {
351 		rc = of_address_to_resource(node, 0, &resm);
352 		of_node_put(node);
353 		if (rc) {
354 			dev_err(dev, "Couldn't address to resource for reserved memory\n");
355 			return -ENODEV;
356 		}
357 
358 		misc_ctrl->mem_size = resource_size(&resm);
359 		misc_ctrl->mem_base = resm.start;
360 	}
361 
362 	misc_ctrl->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
363 	if (IS_ERR(misc_ctrl->regmap)) {
364 		dev_err(dev, "Couldn't get regmap\n");
365 		return -ENODEV;
366 	}
367 
368 	misc_ctrl->config = of_device_get_match_data(dev);
369 
370 	dev_set_drvdata(&pdev->dev, misc_ctrl);
371 
372 	aspeed_p2a_disable_all(misc_ctrl);
373 
374 	misc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
375 	misc_ctrl->miscdev.name = DEVICE_NAME;
376 	misc_ctrl->miscdev.fops = &aspeed_p2a_ctrl_fops;
377 	misc_ctrl->miscdev.parent = dev;
378 
379 	rc = misc_register(&misc_ctrl->miscdev);
380 	if (rc)
381 		dev_err(dev, "Unable to register device\n");
382 
383 	return rc;
384 }
385 
386 static int aspeed_p2a_ctrl_remove(struct platform_device *pdev)
387 {
388 	struct aspeed_p2a_ctrl *p2a_ctrl = dev_get_drvdata(&pdev->dev);
389 
390 	misc_deregister(&p2a_ctrl->miscdev);
391 
392 	return 0;
393 }
394 
395 #define SCU2C_DRAM	BIT(25)
396 #define SCU2C_SPI	BIT(24)
397 #define SCU2C_SOC	BIT(23)
398 #define SCU2C_FLASH	BIT(22)
399 
400 static const struct aspeed_p2a_model_data ast2400_model_data = {
401 	.regions = {
402 		{0x00000000, 0x17FFFFFF, SCU2C_FLASH},
403 		{0x18000000, 0x1FFFFFFF, SCU2C_SOC},
404 		{0x20000000, 0x2FFFFFFF, SCU2C_FLASH},
405 		{0x30000000, 0x3FFFFFFF, SCU2C_SPI},
406 		{0x40000000, 0x5FFFFFFF, SCU2C_DRAM},
407 		{0x60000000, 0xFFFFFFFF, SCU2C_SOC},
408 	}
409 };
410 
411 static const struct aspeed_p2a_model_data ast2500_model_data = {
412 	.regions = {
413 		{0x00000000, 0x0FFFFFFF, SCU2C_FLASH},
414 		{0x10000000, 0x1FFFFFFF, SCU2C_SOC},
415 		{0x20000000, 0x3FFFFFFF, SCU2C_FLASH},
416 		{0x40000000, 0x5FFFFFFF, SCU2C_SOC},
417 		{0x60000000, 0x7FFFFFFF, SCU2C_SPI},
418 		{0x80000000, 0xFFFFFFFF, SCU2C_DRAM},
419 	}
420 };
421 
422 static const struct of_device_id aspeed_p2a_ctrl_match[] = {
423 	{ .compatible = "aspeed,ast2400-p2a-ctrl",
424 	  .data = &ast2400_model_data },
425 	{ .compatible = "aspeed,ast2500-p2a-ctrl",
426 	  .data = &ast2500_model_data },
427 	{ },
428 };
429 
430 static struct platform_driver aspeed_p2a_ctrl_driver = {
431 	.driver = {
432 		.name		= DEVICE_NAME,
433 		.of_match_table = aspeed_p2a_ctrl_match,
434 	},
435 	.probe = aspeed_p2a_ctrl_probe,
436 	.remove = aspeed_p2a_ctrl_remove,
437 };
438 
439 module_platform_driver(aspeed_p2a_ctrl_driver);
440 
441 MODULE_DEVICE_TABLE(of, aspeed_p2a_ctrl_match);
442 MODULE_LICENSE("GPL");
443 MODULE_AUTHOR("Patrick Venture <venture@google.com>");
444 MODULE_DESCRIPTION("Control for aspeed 2400/2500 P2A VGA HOST to BMC mappings");
445