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
aspeed_p2a_enable_bridge(struct aspeed_p2a_ctrl * p2a_ctrl)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
aspeed_p2a_disable_bridge(struct aspeed_p2a_ctrl * p2a_ctrl)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
aspeed_p2a_mmap(struct file * file,struct vm_area_struct * vma)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 + vma_pages(vma) > ctrl->mem_size >> PAGE_SHIFT)
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
aspeed_p2a_region_acquire(struct aspeed_p2a_user * priv,struct aspeed_p2a_ctrl * ctrl,struct aspeed_p2a_ctrl_mapping * map)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
aspeed_p2a_ioctl(struct file * file,unsigned int cmd,unsigned long data)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 */
aspeed_p2a_open(struct inode * inode,struct file * file)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 */
aspeed_p2a_release(struct inode * inode,struct file * file)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 */
aspeed_p2a_disable_all(struct aspeed_p2a_ctrl * p2a_ctrl)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
aspeed_p2a_ctrl_probe(struct platform_device * pdev)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
aspeed_p2a_ctrl_remove(struct platform_device * pdev)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