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.h>
22#include <linux/of_address.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
44struct region {
45	u64 min;
46	u64 max;
47	u32 bit;
48};
49
50struct aspeed_p2a_model_data {
51	/* min, max, bit */
52	struct region regions[P2A_REGION_COUNT];
53};
54
55struct 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
72struct 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
89static 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
95static 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
100static 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
127static 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
172static 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 */
237static 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 */
263static 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
309static 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 */
318static 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
332static 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
386static void 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
393#define SCU2C_DRAM	BIT(25)
394#define SCU2C_SPI	BIT(24)
395#define SCU2C_SOC	BIT(23)
396#define SCU2C_FLASH	BIT(22)
397
398static const struct aspeed_p2a_model_data ast2400_model_data = {
399	.regions = {
400		{0x00000000, 0x17FFFFFF, SCU2C_FLASH},
401		{0x18000000, 0x1FFFFFFF, SCU2C_SOC},
402		{0x20000000, 0x2FFFFFFF, SCU2C_FLASH},
403		{0x30000000, 0x3FFFFFFF, SCU2C_SPI},
404		{0x40000000, 0x5FFFFFFF, SCU2C_DRAM},
405		{0x60000000, 0xFFFFFFFF, SCU2C_SOC},
406	}
407};
408
409static const struct aspeed_p2a_model_data ast2500_model_data = {
410	.regions = {
411		{0x00000000, 0x0FFFFFFF, SCU2C_FLASH},
412		{0x10000000, 0x1FFFFFFF, SCU2C_SOC},
413		{0x20000000, 0x3FFFFFFF, SCU2C_FLASH},
414		{0x40000000, 0x5FFFFFFF, SCU2C_SOC},
415		{0x60000000, 0x7FFFFFFF, SCU2C_SPI},
416		{0x80000000, 0xFFFFFFFF, SCU2C_DRAM},
417	}
418};
419
420static const struct of_device_id aspeed_p2a_ctrl_match[] = {
421	{ .compatible = "aspeed,ast2400-p2a-ctrl",
422	  .data = &ast2400_model_data },
423	{ .compatible = "aspeed,ast2500-p2a-ctrl",
424	  .data = &ast2500_model_data },
425	{ },
426};
427
428static struct platform_driver aspeed_p2a_ctrl_driver = {
429	.driver = {
430		.name		= DEVICE_NAME,
431		.of_match_table = aspeed_p2a_ctrl_match,
432	},
433	.probe = aspeed_p2a_ctrl_probe,
434	.remove_new = aspeed_p2a_ctrl_remove,
435};
436
437module_platform_driver(aspeed_p2a_ctrl_driver);
438
439MODULE_DEVICE_TABLE(of, aspeed_p2a_ctrl_match);
440MODULE_LICENSE("GPL");
441MODULE_AUTHOR("Patrick Venture <venture@google.com>");
442MODULE_DESCRIPTION("Control for aspeed 2400/2500 P2A VGA HOST to BMC mappings");
443