1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Voltage regulators coupler for NVIDIA Tegra30
4 * Copyright (C) 2019 GRATE-DRIVER project
5 *
6 * Voltage constraints borrowed from downstream kernel sources
7 * Copyright (C) 2010-2011 NVIDIA Corporation
8 */
9
10 #define pr_fmt(fmt) "tegra voltage-coupler: " fmt
11
12 #include <linux/init.h>
13 #include <linux/kernel.h>
14 #include <linux/of.h>
15 #include <linux/reboot.h>
16 #include <linux/regulator/coupler.h>
17 #include <linux/regulator/driver.h>
18 #include <linux/regulator/machine.h>
19
20 #include <soc/tegra/fuse.h>
21 #include <soc/tegra/pmc.h>
22
23 struct tegra_regulator_coupler {
24 struct regulator_coupler coupler;
25 struct regulator_dev *core_rdev;
26 struct regulator_dev *cpu_rdev;
27 struct notifier_block reboot_notifier;
28 int core_min_uV, cpu_min_uV;
29 bool sys_reboot_mode_req;
30 bool sys_reboot_mode;
31 };
32
33 static inline struct tegra_regulator_coupler *
to_tegra_coupler(struct regulator_coupler * coupler)34 to_tegra_coupler(struct regulator_coupler *coupler)
35 {
36 return container_of(coupler, struct tegra_regulator_coupler, coupler);
37 }
38
tegra30_core_limit(struct tegra_regulator_coupler * tegra,struct regulator_dev * core_rdev)39 static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
40 struct regulator_dev *core_rdev)
41 {
42 int core_min_uV = 0;
43 int core_max_uV;
44 int core_cur_uV;
45 int err;
46
47 /*
48 * Tegra30 SoC has critical DVFS-capable devices that are
49 * permanently-active or active at a boot time, like EMC
50 * (DRAM controller) or Display controller for example.
51 *
52 * The voltage of a CORE SoC power domain shall not be dropped below
53 * a minimum level, which is determined by device's clock rate.
54 * This means that we can't fully allow CORE voltage scaling until
55 * the state of all DVFS-critical CORE devices is synced.
56 */
57 if (tegra_pmc_core_domain_state_synced() && !tegra->sys_reboot_mode) {
58 pr_info_once("voltage state synced\n");
59 return 0;
60 }
61
62 if (tegra->core_min_uV > 0)
63 return tegra->core_min_uV;
64
65 core_cur_uV = regulator_get_voltage_rdev(core_rdev);
66 if (core_cur_uV < 0)
67 return core_cur_uV;
68
69 core_max_uV = max(core_cur_uV, 1200000);
70
71 err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
72 if (err)
73 return err;
74
75 /*
76 * Limit minimum CORE voltage to a value left from bootloader or,
77 * if it's unreasonably low value, to the most common 1.2v or to
78 * whatever maximum value defined via board's device-tree.
79 */
80 tegra->core_min_uV = core_max_uV;
81
82 pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);
83
84 return tegra->core_min_uV;
85 }
86
tegra30_core_cpu_limit(int cpu_uV)87 static int tegra30_core_cpu_limit(int cpu_uV)
88 {
89 if (cpu_uV < 800000)
90 return 950000;
91
92 if (cpu_uV < 900000)
93 return 1000000;
94
95 if (cpu_uV < 1000000)
96 return 1100000;
97
98 if (cpu_uV < 1100000)
99 return 1200000;
100
101 if (cpu_uV < 1250000) {
102 switch (tegra_sku_info.cpu_speedo_id) {
103 case 0 ... 1:
104 case 4:
105 case 7 ... 8:
106 return 1200000;
107
108 default:
109 return 1300000;
110 }
111 }
112
113 return -EINVAL;
114 }
115
tegra30_voltage_update(struct tegra_regulator_coupler * tegra,struct regulator_dev * cpu_rdev,struct regulator_dev * core_rdev)116 static int tegra30_voltage_update(struct tegra_regulator_coupler *tegra,
117 struct regulator_dev *cpu_rdev,
118 struct regulator_dev *core_rdev)
119 {
120 int core_min_uV, core_max_uV = INT_MAX;
121 int cpu_min_uV, cpu_max_uV = INT_MAX;
122 int cpu_min_uV_consumers = 0;
123 int core_min_limited_uV;
124 int core_target_uV;
125 int cpu_target_uV;
126 int core_max_step;
127 int cpu_max_step;
128 int max_spread;
129 int core_uV;
130 int cpu_uV;
131 int err;
132
133 /*
134 * CPU voltage should not got lower than 300mV from the CORE.
135 * CPU voltage should stay below the CORE by 100mV+, depending
136 * by the CORE voltage. This applies to all Tegra30 SoC's.
137 */
138 max_spread = cpu_rdev->constraints->max_spread[0];
139 cpu_max_step = cpu_rdev->constraints->max_uV_step;
140 core_max_step = core_rdev->constraints->max_uV_step;
141
142 if (!max_spread) {
143 pr_err_once("cpu-core max-spread is undefined in device-tree\n");
144 max_spread = 300000;
145 }
146
147 if (!cpu_max_step) {
148 pr_err_once("cpu max-step is undefined in device-tree\n");
149 cpu_max_step = 150000;
150 }
151
152 if (!core_max_step) {
153 pr_err_once("core max-step is undefined in device-tree\n");
154 core_max_step = 150000;
155 }
156
157 /*
158 * The CORE voltage scaling is currently not hooked up in drivers,
159 * hence we will limit the minimum CORE voltage to a reasonable value.
160 * This should be good enough for the time being.
161 */
162 core_min_uV = tegra30_core_limit(tegra, core_rdev);
163 if (core_min_uV < 0)
164 return core_min_uV;
165
166 err = regulator_check_consumers(core_rdev, &core_min_uV, &core_max_uV,
167 PM_SUSPEND_ON);
168 if (err)
169 return err;
170
171 core_uV = regulator_get_voltage_rdev(core_rdev);
172 if (core_uV < 0)
173 return core_uV;
174
175 cpu_min_uV = core_min_uV - max_spread;
176
177 err = regulator_check_consumers(cpu_rdev, &cpu_min_uV, &cpu_max_uV,
178 PM_SUSPEND_ON);
179 if (err)
180 return err;
181
182 err = regulator_check_consumers(cpu_rdev, &cpu_min_uV_consumers,
183 &cpu_max_uV, PM_SUSPEND_ON);
184 if (err)
185 return err;
186
187 err = regulator_check_voltage(cpu_rdev, &cpu_min_uV, &cpu_max_uV);
188 if (err)
189 return err;
190
191 cpu_uV = regulator_get_voltage_rdev(cpu_rdev);
192 if (cpu_uV < 0)
193 return cpu_uV;
194
195 /* store boot voltage level */
196 if (!tegra->cpu_min_uV)
197 tegra->cpu_min_uV = cpu_uV;
198
199 /*
200 * CPU's regulator may not have any consumers, hence the voltage
201 * must not be changed in that case because CPU simply won't
202 * survive the voltage drop if it's running on a higher frequency.
203 */
204 if (!cpu_min_uV_consumers)
205 cpu_min_uV = max(cpu_uV, cpu_min_uV);
206
207 /*
208 * Bootloader shall set up voltages correctly, but if it
209 * happens that there is a violation, then try to fix it
210 * at first.
211 */
212 core_min_limited_uV = tegra30_core_cpu_limit(cpu_uV);
213 if (core_min_limited_uV < 0)
214 return core_min_limited_uV;
215
216 core_min_uV = max(core_min_uV, tegra30_core_cpu_limit(cpu_min_uV));
217
218 err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
219 if (err)
220 return err;
221
222 /* restore boot voltage level */
223 if (tegra->sys_reboot_mode)
224 cpu_min_uV = max(cpu_min_uV, tegra->cpu_min_uV);
225
226 if (core_min_limited_uV > core_uV) {
227 pr_err("core voltage constraint violated: %d %d %d\n",
228 core_uV, core_min_limited_uV, cpu_uV);
229 goto update_core;
230 }
231
232 while (cpu_uV != cpu_min_uV || core_uV != core_min_uV) {
233 if (cpu_uV < cpu_min_uV) {
234 cpu_target_uV = min(cpu_uV + cpu_max_step, cpu_min_uV);
235 } else {
236 cpu_target_uV = max(cpu_uV - cpu_max_step, cpu_min_uV);
237 cpu_target_uV = max(core_uV - max_spread, cpu_target_uV);
238 }
239
240 if (cpu_uV == cpu_target_uV)
241 goto update_core;
242
243 err = regulator_set_voltage_rdev(cpu_rdev,
244 cpu_target_uV,
245 cpu_max_uV,
246 PM_SUSPEND_ON);
247 if (err)
248 return err;
249
250 cpu_uV = cpu_target_uV;
251 update_core:
252 core_min_limited_uV = tegra30_core_cpu_limit(cpu_uV);
253 if (core_min_limited_uV < 0)
254 return core_min_limited_uV;
255
256 core_target_uV = max(core_min_limited_uV, core_min_uV);
257
258 if (core_uV < core_target_uV) {
259 core_target_uV = min(core_target_uV, core_uV + core_max_step);
260 core_target_uV = min(core_target_uV, cpu_uV + max_spread);
261 } else {
262 core_target_uV = max(core_target_uV, core_uV - core_max_step);
263 }
264
265 if (core_uV == core_target_uV)
266 continue;
267
268 err = regulator_set_voltage_rdev(core_rdev,
269 core_target_uV,
270 core_max_uV,
271 PM_SUSPEND_ON);
272 if (err)
273 return err;
274
275 core_uV = core_target_uV;
276 }
277
278 return 0;
279 }
280
tegra30_regulator_balance_voltage(struct regulator_coupler * coupler,struct regulator_dev * rdev,suspend_state_t state)281 static int tegra30_regulator_balance_voltage(struct regulator_coupler *coupler,
282 struct regulator_dev *rdev,
283 suspend_state_t state)
284 {
285 struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
286 struct regulator_dev *core_rdev = tegra->core_rdev;
287 struct regulator_dev *cpu_rdev = tegra->cpu_rdev;
288
289 if ((core_rdev != rdev && cpu_rdev != rdev) || state != PM_SUSPEND_ON) {
290 pr_err("regulators are not coupled properly\n");
291 return -EINVAL;
292 }
293
294 tegra->sys_reboot_mode = READ_ONCE(tegra->sys_reboot_mode_req);
295
296 return tegra30_voltage_update(tegra, cpu_rdev, core_rdev);
297 }
298
tegra30_regulator_prepare_reboot(struct tegra_regulator_coupler * tegra,bool sys_reboot_mode)299 static int tegra30_regulator_prepare_reboot(struct tegra_regulator_coupler *tegra,
300 bool sys_reboot_mode)
301 {
302 int err;
303
304 if (!tegra->core_rdev || !tegra->cpu_rdev)
305 return 0;
306
307 WRITE_ONCE(tegra->sys_reboot_mode_req, true);
308
309 /*
310 * Some devices use CPU soft-reboot method and in this case we
311 * should ensure that voltages are sane for the reboot by restoring
312 * the minimum boot levels.
313 */
314 err = regulator_sync_voltage_rdev(tegra->cpu_rdev);
315 if (err)
316 return err;
317
318 err = regulator_sync_voltage_rdev(tegra->core_rdev);
319 if (err)
320 return err;
321
322 WRITE_ONCE(tegra->sys_reboot_mode_req, sys_reboot_mode);
323
324 return 0;
325 }
326
tegra30_regulator_reboot(struct notifier_block * notifier,unsigned long event,void * cmd)327 static int tegra30_regulator_reboot(struct notifier_block *notifier,
328 unsigned long event, void *cmd)
329 {
330 struct tegra_regulator_coupler *tegra;
331 int ret;
332
333 if (event != SYS_RESTART)
334 return NOTIFY_DONE;
335
336 tegra = container_of(notifier, struct tegra_regulator_coupler,
337 reboot_notifier);
338
339 ret = tegra30_regulator_prepare_reboot(tegra, true);
340
341 return notifier_from_errno(ret);
342 }
343
tegra30_regulator_attach(struct regulator_coupler * coupler,struct regulator_dev * rdev)344 static int tegra30_regulator_attach(struct regulator_coupler *coupler,
345 struct regulator_dev *rdev)
346 {
347 struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
348 struct device_node *np = rdev->dev.of_node;
349
350 if (of_property_read_bool(np, "nvidia,tegra-core-regulator") &&
351 !tegra->core_rdev) {
352 tegra->core_rdev = rdev;
353 return 0;
354 }
355
356 if (of_property_read_bool(np, "nvidia,tegra-cpu-regulator") &&
357 !tegra->cpu_rdev) {
358 tegra->cpu_rdev = rdev;
359 return 0;
360 }
361
362 return -EINVAL;
363 }
364
tegra30_regulator_detach(struct regulator_coupler * coupler,struct regulator_dev * rdev)365 static int tegra30_regulator_detach(struct regulator_coupler *coupler,
366 struct regulator_dev *rdev)
367 {
368 struct tegra_regulator_coupler *tegra = to_tegra_coupler(coupler);
369
370 /*
371 * We don't expect regulators to be decoupled during reboot,
372 * this may race with the reboot handler and shouldn't ever
373 * happen in practice.
374 */
375 if (WARN_ON_ONCE(system_state > SYSTEM_RUNNING))
376 return -EPERM;
377
378 if (tegra->core_rdev == rdev) {
379 tegra->core_rdev = NULL;
380 return 0;
381 }
382
383 if (tegra->cpu_rdev == rdev) {
384 tegra->cpu_rdev = NULL;
385 return 0;
386 }
387
388 return -EINVAL;
389 }
390
391 static struct tegra_regulator_coupler tegra30_coupler = {
392 .coupler = {
393 .attach_regulator = tegra30_regulator_attach,
394 .detach_regulator = tegra30_regulator_detach,
395 .balance_voltage = tegra30_regulator_balance_voltage,
396 },
397 .reboot_notifier.notifier_call = tegra30_regulator_reboot,
398 };
399
tegra_regulator_coupler_init(void)400 static int __init tegra_regulator_coupler_init(void)
401 {
402 int err;
403
404 if (!of_machine_is_compatible("nvidia,tegra30"))
405 return 0;
406
407 err = register_reboot_notifier(&tegra30_coupler.reboot_notifier);
408 WARN_ON(err);
409
410 return regulator_coupler_register(&tegra30_coupler.coupler);
411 }
412 arch_initcall(tegra_regulator_coupler_init);
413