xref: /openbmc/linux/drivers/pci/vc.c (revision 9b41d19a)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * PCI Virtual Channel support
4  *
5  * Copyright (C) 2013 Red Hat, Inc.  All rights reserved.
6  *     Author: Alex Williamson <alex.williamson@redhat.com>
7  */
8 
9 #include <linux/device.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/pci.h>
13 #include <linux/pci_regs.h>
14 #include <linux/types.h>
15 
16 #include "pci.h"
17 
18 /**
19  * pci_vc_save_restore_dwords - Save or restore a series of dwords
20  * @dev: device
21  * @pos: starting config space position
22  * @buf: buffer to save to or restore from
23  * @dwords: number of dwords to save/restore
24  * @save: whether to save or restore
25  */
pci_vc_save_restore_dwords(struct pci_dev * dev,int pos,u32 * buf,int dwords,bool save)26 static void pci_vc_save_restore_dwords(struct pci_dev *dev, int pos,
27 				       u32 *buf, int dwords, bool save)
28 {
29 	int i;
30 
31 	for (i = 0; i < dwords; i++, buf++) {
32 		if (save)
33 			pci_read_config_dword(dev, pos + (i * 4), buf);
34 		else
35 			pci_write_config_dword(dev, pos + (i * 4), *buf);
36 	}
37 }
38 
39 /**
40  * pci_vc_load_arb_table - load and wait for VC arbitration table
41  * @dev: device
42  * @pos: starting position of VC capability (VC/VC9/MFVC)
43  *
44  * Set Load VC Arbitration Table bit requesting hardware to apply the VC
45  * Arbitration Table (previously loaded).  When the VC Arbitration Table
46  * Status clears, hardware has latched the table into VC arbitration logic.
47  */
pci_vc_load_arb_table(struct pci_dev * dev,int pos)48 static void pci_vc_load_arb_table(struct pci_dev *dev, int pos)
49 {
50 	u16 ctrl;
51 
52 	pci_read_config_word(dev, pos + PCI_VC_PORT_CTRL, &ctrl);
53 	pci_write_config_word(dev, pos + PCI_VC_PORT_CTRL,
54 			      ctrl | PCI_VC_PORT_CTRL_LOAD_TABLE);
55 	if (pci_wait_for_pending(dev, pos + PCI_VC_PORT_STATUS,
56 				 PCI_VC_PORT_STATUS_TABLE))
57 		return;
58 
59 	pci_err(dev, "VC arbitration table failed to load\n");
60 }
61 
62 /**
63  * pci_vc_load_port_arb_table - Load and wait for VC port arbitration table
64  * @dev: device
65  * @pos: starting position of VC capability (VC/VC9/MFVC)
66  * @res: VC resource number, ie. VCn (0-7)
67  *
68  * Set Load Port Arbitration Table bit requesting hardware to apply the Port
69  * Arbitration Table (previously loaded).  When the Port Arbitration Table
70  * Status clears, hardware has latched the table into port arbitration logic.
71  */
pci_vc_load_port_arb_table(struct pci_dev * dev,int pos,int res)72 static void pci_vc_load_port_arb_table(struct pci_dev *dev, int pos, int res)
73 {
74 	int ctrl_pos, status_pos;
75 	u32 ctrl;
76 
77 	ctrl_pos = pos + PCI_VC_RES_CTRL + (res * PCI_CAP_VC_PER_VC_SIZEOF);
78 	status_pos = pos + PCI_VC_RES_STATUS + (res * PCI_CAP_VC_PER_VC_SIZEOF);
79 
80 	pci_read_config_dword(dev, ctrl_pos, &ctrl);
81 	pci_write_config_dword(dev, ctrl_pos,
82 			       ctrl | PCI_VC_RES_CTRL_LOAD_TABLE);
83 
84 	if (pci_wait_for_pending(dev, status_pos, PCI_VC_RES_STATUS_TABLE))
85 		return;
86 
87 	pci_err(dev, "VC%d port arbitration table failed to load\n", res);
88 }
89 
90 /**
91  * pci_vc_enable - Enable virtual channel
92  * @dev: device
93  * @pos: starting position of VC capability (VC/VC9/MFVC)
94  * @res: VC res number, ie. VCn (0-7)
95  *
96  * A VC is enabled by setting the enable bit in matching resource control
97  * registers on both sides of a link.  We therefore need to find the opposite
98  * end of the link.  To keep this simple we enable from the downstream device.
99  * RC devices do not have an upstream device, nor does it seem that VC9 do
100  * (spec is unclear).  Once we find the upstream device, match the VC ID to
101  * get the correct resource, disable and enable on both ends.
102  */
pci_vc_enable(struct pci_dev * dev,int pos,int res)103 static void pci_vc_enable(struct pci_dev *dev, int pos, int res)
104 {
105 	int ctrl_pos, status_pos, id, pos2, evcc, i, ctrl_pos2, status_pos2;
106 	u32 ctrl, header, cap1, ctrl2;
107 	struct pci_dev *link = NULL;
108 
109 	/* Enable VCs from the downstream device */
110 	if (!pci_is_pcie(dev) || !pcie_downstream_port(dev))
111 		return;
112 
113 	ctrl_pos = pos + PCI_VC_RES_CTRL + (res * PCI_CAP_VC_PER_VC_SIZEOF);
114 	status_pos = pos + PCI_VC_RES_STATUS + (res * PCI_CAP_VC_PER_VC_SIZEOF);
115 
116 	pci_read_config_dword(dev, ctrl_pos, &ctrl);
117 	id = ctrl & PCI_VC_RES_CTRL_ID;
118 
119 	pci_read_config_dword(dev, pos, &header);
120 
121 	/* If there is no opposite end of the link, skip to enable */
122 	if (PCI_EXT_CAP_ID(header) == PCI_EXT_CAP_ID_VC9 ||
123 	    pci_is_root_bus(dev->bus))
124 		goto enable;
125 
126 	pos2 = pci_find_ext_capability(dev->bus->self, PCI_EXT_CAP_ID_VC);
127 	if (!pos2)
128 		goto enable;
129 
130 	pci_read_config_dword(dev->bus->self, pos2 + PCI_VC_PORT_CAP1, &cap1);
131 	evcc = cap1 & PCI_VC_CAP1_EVCC;
132 
133 	/* VC0 is hardwired enabled, so we can start with 1 */
134 	for (i = 1; i < evcc + 1; i++) {
135 		ctrl_pos2 = pos2 + PCI_VC_RES_CTRL +
136 				(i * PCI_CAP_VC_PER_VC_SIZEOF);
137 		status_pos2 = pos2 + PCI_VC_RES_STATUS +
138 				(i * PCI_CAP_VC_PER_VC_SIZEOF);
139 		pci_read_config_dword(dev->bus->self, ctrl_pos2, &ctrl2);
140 		if ((ctrl2 & PCI_VC_RES_CTRL_ID) == id) {
141 			link = dev->bus->self;
142 			break;
143 		}
144 	}
145 
146 	if (!link)
147 		goto enable;
148 
149 	/* Disable if enabled */
150 	if (ctrl2 & PCI_VC_RES_CTRL_ENABLE) {
151 		ctrl2 &= ~PCI_VC_RES_CTRL_ENABLE;
152 		pci_write_config_dword(link, ctrl_pos2, ctrl2);
153 	}
154 
155 	/* Enable on both ends */
156 	ctrl2 |= PCI_VC_RES_CTRL_ENABLE;
157 	pci_write_config_dword(link, ctrl_pos2, ctrl2);
158 enable:
159 	ctrl |= PCI_VC_RES_CTRL_ENABLE;
160 	pci_write_config_dword(dev, ctrl_pos, ctrl);
161 
162 	if (!pci_wait_for_pending(dev, status_pos, PCI_VC_RES_STATUS_NEGO))
163 		pci_err(dev, "VC%d negotiation stuck pending\n", id);
164 
165 	if (link && !pci_wait_for_pending(link, status_pos2,
166 					  PCI_VC_RES_STATUS_NEGO))
167 		pci_err(link, "VC%d negotiation stuck pending\n", id);
168 }
169 
170 /**
171  * pci_vc_do_save_buffer - Size, save, or restore VC state
172  * @dev: device
173  * @pos: starting position of VC capability (VC/VC9/MFVC)
174  * @save_state: buffer for save/restore
175  * @save: if provided a buffer, this indicates what to do with it
176  *
177  * Walking Virtual Channel config space to size, save, or restore it
178  * is complicated, so we do it all from one function to reduce code and
179  * guarantee ordering matches in the buffer.  When called with NULL
180  * @save_state, return the size of the necessary save buffer.  When called
181  * with a non-NULL @save_state, @save determines whether we save to the
182  * buffer or restore from it.
183  */
pci_vc_do_save_buffer(struct pci_dev * dev,int pos,struct pci_cap_saved_state * save_state,bool save)184 static int pci_vc_do_save_buffer(struct pci_dev *dev, int pos,
185 				 struct pci_cap_saved_state *save_state,
186 				 bool save)
187 {
188 	u32 cap1;
189 	char evcc, lpevcc, parb_size;
190 	int i, len = 0;
191 	u8 *buf = save_state ? (u8 *)save_state->cap.data : NULL;
192 
193 	/* Sanity check buffer size for save/restore */
194 	if (buf && save_state->cap.size !=
195 	    pci_vc_do_save_buffer(dev, pos, NULL, save)) {
196 		pci_err(dev, "VC save buffer size does not match @0x%x\n", pos);
197 		return -ENOMEM;
198 	}
199 
200 	pci_read_config_dword(dev, pos + PCI_VC_PORT_CAP1, &cap1);
201 	/* Extended VC Count (not counting VC0) */
202 	evcc = cap1 & PCI_VC_CAP1_EVCC;
203 	/* Low Priority Extended VC Count (not counting VC0) */
204 	lpevcc = (cap1 & PCI_VC_CAP1_LPEVCC) >> 4;
205 	/* Port Arbitration Table Entry Size (bits) */
206 	parb_size = 1 << ((cap1 & PCI_VC_CAP1_ARB_SIZE) >> 10);
207 
208 	/*
209 	 * Port VC Control Register contains VC Arbitration Select, which
210 	 * cannot be modified when more than one LPVC is in operation.  We
211 	 * therefore save/restore it first, as only VC0 should be enabled
212 	 * after device reset.
213 	 */
214 	if (buf) {
215 		if (save)
216 			pci_read_config_word(dev, pos + PCI_VC_PORT_CTRL,
217 					     (u16 *)buf);
218 		else
219 			pci_write_config_word(dev, pos + PCI_VC_PORT_CTRL,
220 					      *(u16 *)buf);
221 		buf += 4;
222 	}
223 	len += 4;
224 
225 	/*
226 	 * If we have any Low Priority VCs and a VC Arbitration Table Offset
227 	 * in Port VC Capability Register 2 then save/restore it next.
228 	 */
229 	if (lpevcc) {
230 		u32 cap2;
231 		int vcarb_offset;
232 
233 		pci_read_config_dword(dev, pos + PCI_VC_PORT_CAP2, &cap2);
234 		vcarb_offset = ((cap2 & PCI_VC_CAP2_ARB_OFF) >> 24) * 16;
235 
236 		if (vcarb_offset) {
237 			int size, vcarb_phases = 0;
238 
239 			if (cap2 & PCI_VC_CAP2_128_PHASE)
240 				vcarb_phases = 128;
241 			else if (cap2 & PCI_VC_CAP2_64_PHASE)
242 				vcarb_phases = 64;
243 			else if (cap2 & PCI_VC_CAP2_32_PHASE)
244 				vcarb_phases = 32;
245 
246 			/* Fixed 4 bits per phase per lpevcc (plus VC0) */
247 			size = ((lpevcc + 1) * vcarb_phases * 4) / 8;
248 
249 			if (size && buf) {
250 				pci_vc_save_restore_dwords(dev,
251 							   pos + vcarb_offset,
252 							   (u32 *)buf,
253 							   size / 4, save);
254 				/*
255 				 * On restore, we need to signal hardware to
256 				 * re-load the VC Arbitration Table.
257 				 */
258 				if (!save)
259 					pci_vc_load_arb_table(dev, pos);
260 
261 				buf += size;
262 			}
263 			len += size;
264 		}
265 	}
266 
267 	/*
268 	 * In addition to each VC Resource Control Register, we may have a
269 	 * Port Arbitration Table attached to each VC.  The Port Arbitration
270 	 * Table Offset in each VC Resource Capability Register tells us if
271 	 * it exists.  The entry size is global from the Port VC Capability
272 	 * Register1 above.  The number of phases is determined per VC.
273 	 */
274 	for (i = 0; i < evcc + 1; i++) {
275 		u32 cap;
276 		int parb_offset;
277 
278 		pci_read_config_dword(dev, pos + PCI_VC_RES_CAP +
279 				      (i * PCI_CAP_VC_PER_VC_SIZEOF), &cap);
280 		parb_offset = ((cap & PCI_VC_RES_CAP_ARB_OFF) >> 24) * 16;
281 		if (parb_offset) {
282 			int size, parb_phases = 0;
283 
284 			if (cap & PCI_VC_RES_CAP_256_PHASE)
285 				parb_phases = 256;
286 			else if (cap & (PCI_VC_RES_CAP_128_PHASE |
287 					PCI_VC_RES_CAP_128_PHASE_TB))
288 				parb_phases = 128;
289 			else if (cap & PCI_VC_RES_CAP_64_PHASE)
290 				parb_phases = 64;
291 			else if (cap & PCI_VC_RES_CAP_32_PHASE)
292 				parb_phases = 32;
293 
294 			size = (parb_size * parb_phases) / 8;
295 
296 			if (size && buf) {
297 				pci_vc_save_restore_dwords(dev,
298 							   pos + parb_offset,
299 							   (u32 *)buf,
300 							   size / 4, save);
301 				buf += size;
302 			}
303 			len += size;
304 		}
305 
306 		/* VC Resource Control Register */
307 		if (buf) {
308 			int ctrl_pos = pos + PCI_VC_RES_CTRL +
309 						(i * PCI_CAP_VC_PER_VC_SIZEOF);
310 			if (save)
311 				pci_read_config_dword(dev, ctrl_pos,
312 						      (u32 *)buf);
313 			else {
314 				u32 tmp, ctrl = *(u32 *)buf;
315 				/*
316 				 * For an FLR case, the VC config may remain.
317 				 * Preserve enable bit, restore the rest.
318 				 */
319 				pci_read_config_dword(dev, ctrl_pos, &tmp);
320 				tmp &= PCI_VC_RES_CTRL_ENABLE;
321 				tmp |= ctrl & ~PCI_VC_RES_CTRL_ENABLE;
322 				pci_write_config_dword(dev, ctrl_pos, tmp);
323 				/* Load port arbitration table if used */
324 				if (ctrl & PCI_VC_RES_CTRL_ARB_SELECT)
325 					pci_vc_load_port_arb_table(dev, pos, i);
326 				/* Re-enable if needed */
327 				if ((ctrl ^ tmp) & PCI_VC_RES_CTRL_ENABLE)
328 					pci_vc_enable(dev, pos, i);
329 			}
330 			buf += 4;
331 		}
332 		len += 4;
333 	}
334 
335 	return buf ? 0 : len;
336 }
337 
338 static struct {
339 	u16 id;
340 	const char *name;
341 } vc_caps[] = { { PCI_EXT_CAP_ID_MFVC, "MFVC" },
342 		{ PCI_EXT_CAP_ID_VC, "VC" },
343 		{ PCI_EXT_CAP_ID_VC9, "VC9" } };
344 
345 /**
346  * pci_save_vc_state - Save VC state to pre-allocate save buffer
347  * @dev: device
348  *
349  * For each type of VC capability, VC/VC9/MFVC, find the capability and
350  * save it to the pre-allocated save buffer.
351  */
pci_save_vc_state(struct pci_dev * dev)352 int pci_save_vc_state(struct pci_dev *dev)
353 {
354 	int i;
355 
356 	for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
357 		int pos, ret;
358 		struct pci_cap_saved_state *save_state;
359 
360 		pos = pci_find_ext_capability(dev, vc_caps[i].id);
361 		if (!pos)
362 			continue;
363 
364 		save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
365 		if (!save_state) {
366 			pci_err(dev, "%s buffer not found in %s\n",
367 				vc_caps[i].name, __func__);
368 			return -ENOMEM;
369 		}
370 
371 		ret = pci_vc_do_save_buffer(dev, pos, save_state, true);
372 		if (ret) {
373 			pci_err(dev, "%s save unsuccessful %s\n",
374 				vc_caps[i].name, __func__);
375 			return ret;
376 		}
377 	}
378 
379 	return 0;
380 }
381 
382 /**
383  * pci_restore_vc_state - Restore VC state from save buffer
384  * @dev: device
385  *
386  * For each type of VC capability, VC/VC9/MFVC, find the capability and
387  * restore it from the previously saved buffer.
388  */
pci_restore_vc_state(struct pci_dev * dev)389 void pci_restore_vc_state(struct pci_dev *dev)
390 {
391 	int i;
392 
393 	for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
394 		int pos;
395 		struct pci_cap_saved_state *save_state;
396 
397 		pos = pci_find_ext_capability(dev, vc_caps[i].id);
398 		save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
399 		if (!save_state || !pos)
400 			continue;
401 
402 		pci_vc_do_save_buffer(dev, pos, save_state, false);
403 	}
404 }
405 
406 /**
407  * pci_allocate_vc_save_buffers - Allocate save buffers for VC caps
408  * @dev: device
409  *
410  * For each type of VC capability, VC/VC9/MFVC, find the capability, size
411  * it, and allocate a buffer for save/restore.
412  */
pci_allocate_vc_save_buffers(struct pci_dev * dev)413 void pci_allocate_vc_save_buffers(struct pci_dev *dev)
414 {
415 	int i;
416 
417 	for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
418 		int len, pos = pci_find_ext_capability(dev, vc_caps[i].id);
419 
420 		if (!pos)
421 			continue;
422 
423 		len = pci_vc_do_save_buffer(dev, pos, NULL, false);
424 		if (pci_add_ext_cap_save_buffer(dev, vc_caps[i].id, len))
425 			pci_err(dev, "unable to preallocate %s save buffer\n",
426 				vc_caps[i].name);
427 	}
428 }
429