1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Raspberry Pi driver for firmware controlled clocks
4  *
5  * Even though clk-bcm2835 provides an interface to the hardware registers for
6  * the system clocks we've had to factor out 'pllb' as the firmware 'owns' it.
7  * We're not allowed to change it directly as we might race with the
8  * over-temperature and under-voltage protections provided by the firmware.
9  *
10  * Copyright (C) 2019 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
11  */
12 
13 #include <linux/clkdev.h>
14 #include <linux/clk-provider.h>
15 #include <linux/io.h>
16 #include <linux/module.h>
17 #include <linux/platform_device.h>
18 
19 #include <soc/bcm2835/raspberrypi-firmware.h>
20 
21 enum rpi_firmware_clk_id {
22 	RPI_FIRMWARE_EMMC_CLK_ID = 1,
23 	RPI_FIRMWARE_UART_CLK_ID,
24 	RPI_FIRMWARE_ARM_CLK_ID,
25 	RPI_FIRMWARE_CORE_CLK_ID,
26 	RPI_FIRMWARE_V3D_CLK_ID,
27 	RPI_FIRMWARE_H264_CLK_ID,
28 	RPI_FIRMWARE_ISP_CLK_ID,
29 	RPI_FIRMWARE_SDRAM_CLK_ID,
30 	RPI_FIRMWARE_PIXEL_CLK_ID,
31 	RPI_FIRMWARE_PWM_CLK_ID,
32 	RPI_FIRMWARE_HEVC_CLK_ID,
33 	RPI_FIRMWARE_EMMC2_CLK_ID,
34 	RPI_FIRMWARE_M2MC_CLK_ID,
35 	RPI_FIRMWARE_PIXEL_BVB_CLK_ID,
36 	RPI_FIRMWARE_NUM_CLK_ID,
37 };
38 
39 static char *rpi_firmware_clk_names[] = {
40 	[RPI_FIRMWARE_EMMC_CLK_ID]	= "emmc",
41 	[RPI_FIRMWARE_UART_CLK_ID]	= "uart",
42 	[RPI_FIRMWARE_ARM_CLK_ID]	= "arm",
43 	[RPI_FIRMWARE_CORE_CLK_ID]	= "core",
44 	[RPI_FIRMWARE_V3D_CLK_ID]	= "v3d",
45 	[RPI_FIRMWARE_H264_CLK_ID]	= "h264",
46 	[RPI_FIRMWARE_ISP_CLK_ID]	= "isp",
47 	[RPI_FIRMWARE_SDRAM_CLK_ID]	= "sdram",
48 	[RPI_FIRMWARE_PIXEL_CLK_ID]	= "pixel",
49 	[RPI_FIRMWARE_PWM_CLK_ID]	= "pwm",
50 	[RPI_FIRMWARE_HEVC_CLK_ID]	= "hevc",
51 	[RPI_FIRMWARE_EMMC2_CLK_ID]	= "emmc2",
52 	[RPI_FIRMWARE_M2MC_CLK_ID]	= "m2mc",
53 	[RPI_FIRMWARE_PIXEL_BVB_CLK_ID]	= "pixel-bvb",
54 };
55 
56 #define RPI_FIRMWARE_STATE_ENABLE_BIT	BIT(0)
57 #define RPI_FIRMWARE_STATE_WAIT_BIT	BIT(1)
58 
59 struct raspberrypi_clk_variant;
60 
61 struct raspberrypi_clk {
62 	struct device *dev;
63 	struct rpi_firmware *firmware;
64 	struct platform_device *cpufreq;
65 };
66 
67 struct raspberrypi_clk_data {
68 	struct clk_hw hw;
69 
70 	unsigned int id;
71 	struct raspberrypi_clk_variant *variant;
72 
73 	struct raspberrypi_clk *rpi;
74 };
75 
76 struct raspberrypi_clk_variant {
77 	bool		export;
78 	char		*clkdev;
79 	unsigned long	min_rate;
80 	bool		minimize;
81 };
82 
83 static struct raspberrypi_clk_variant
84 raspberrypi_clk_variants[RPI_FIRMWARE_NUM_CLK_ID] = {
85 	[RPI_FIRMWARE_ARM_CLK_ID] = {
86 		.export = true,
87 		.clkdev = "cpu0",
88 	},
89 	[RPI_FIRMWARE_CORE_CLK_ID] = {
90 		.export = true,
91 
92 		/*
93 		 * The clock is shared between the HVS and the CSI
94 		 * controllers, on the BCM2711 and will change depending
95 		 * on the pixels composited on the HVS and the capture
96 		 * resolution on Unicam.
97 		 *
98 		 * Since the rate can get quite large, and we need to
99 		 * coordinate between both driver instances, let's
100 		 * always use the minimum the drivers will let us.
101 		 */
102 		.minimize = true,
103 	},
104 	[RPI_FIRMWARE_M2MC_CLK_ID] = {
105 		.export = true,
106 
107 		/*
108 		 * If we boot without any cable connected to any of the
109 		 * HDMI connector, the firmware will skip the HSM
110 		 * initialization and leave it with a rate of 0,
111 		 * resulting in a bus lockup when we're accessing the
112 		 * registers even if it's enabled.
113 		 *
114 		 * Let's put a sensible default so that we don't end up
115 		 * in this situation.
116 		 */
117 		.min_rate = 120000000,
118 
119 		/*
120 		 * The clock is shared between the two HDMI controllers
121 		 * on the BCM2711 and will change depending on the
122 		 * resolution output on each. Since the rate can get
123 		 * quite large, and we need to coordinate between both
124 		 * driver instances, let's always use the minimum the
125 		 * drivers will let us.
126 		 */
127 		.minimize = true,
128 	},
129 	[RPI_FIRMWARE_V3D_CLK_ID] = {
130 		.export = true,
131 	},
132 	[RPI_FIRMWARE_PIXEL_BVB_CLK_ID] = {
133 		.export = true,
134 	},
135 };
136 
137 /*
138  * Structure of the message passed to Raspberry Pi's firmware in order to
139  * change clock rates. The 'disable_turbo' option is only available to the ARM
140  * clock (pllb) which we enable by default as turbo mode will alter multiple
141  * clocks at once.
142  *
143  * Even though we're able to access the clock registers directly we're bound to
144  * use the firmware interface as the firmware ultimately takes care of
145  * mitigating overheating/undervoltage situations and we would be changing
146  * frequencies behind his back.
147  *
148  * For more information on the firmware interface check:
149  * https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
150  */
151 struct raspberrypi_firmware_prop {
152 	__le32 id;
153 	__le32 val;
154 	__le32 disable_turbo;
155 } __packed;
156 
157 static int raspberrypi_clock_property(struct rpi_firmware *firmware,
158 				      const struct raspberrypi_clk_data *data,
159 				      u32 tag, u32 *val)
160 {
161 	struct raspberrypi_firmware_prop msg = {
162 		.id = cpu_to_le32(data->id),
163 		.val = cpu_to_le32(*val),
164 		.disable_turbo = cpu_to_le32(1),
165 	};
166 	int ret;
167 
168 	ret = rpi_firmware_property(firmware, tag, &msg, sizeof(msg));
169 	if (ret)
170 		return ret;
171 
172 	*val = le32_to_cpu(msg.val);
173 
174 	return 0;
175 }
176 
177 static int raspberrypi_fw_is_prepared(struct clk_hw *hw)
178 {
179 	struct raspberrypi_clk_data *data =
180 		container_of(hw, struct raspberrypi_clk_data, hw);
181 	struct raspberrypi_clk *rpi = data->rpi;
182 	u32 val = 0;
183 	int ret;
184 
185 	ret = raspberrypi_clock_property(rpi->firmware, data,
186 					 RPI_FIRMWARE_GET_CLOCK_STATE, &val);
187 	if (ret)
188 		return 0;
189 
190 	return !!(val & RPI_FIRMWARE_STATE_ENABLE_BIT);
191 }
192 
193 
194 static unsigned long raspberrypi_fw_get_rate(struct clk_hw *hw,
195 					     unsigned long parent_rate)
196 {
197 	struct raspberrypi_clk_data *data =
198 		container_of(hw, struct raspberrypi_clk_data, hw);
199 	struct raspberrypi_clk *rpi = data->rpi;
200 	u32 val = 0;
201 	int ret;
202 
203 	ret = raspberrypi_clock_property(rpi->firmware, data,
204 					 RPI_FIRMWARE_GET_CLOCK_RATE, &val);
205 	if (ret)
206 		return ret;
207 
208 	return val;
209 }
210 
211 static int raspberrypi_fw_set_rate(struct clk_hw *hw, unsigned long rate,
212 				   unsigned long parent_rate)
213 {
214 	struct raspberrypi_clk_data *data =
215 		container_of(hw, struct raspberrypi_clk_data, hw);
216 	struct raspberrypi_clk *rpi = data->rpi;
217 	u32 _rate = rate;
218 	int ret;
219 
220 	ret = raspberrypi_clock_property(rpi->firmware, data,
221 					 RPI_FIRMWARE_SET_CLOCK_RATE, &_rate);
222 	if (ret)
223 		dev_err_ratelimited(rpi->dev, "Failed to change %s frequency: %d",
224 				    clk_hw_get_name(hw), ret);
225 
226 	return ret;
227 }
228 
229 static int raspberrypi_fw_dumb_determine_rate(struct clk_hw *hw,
230 					      struct clk_rate_request *req)
231 {
232 	struct raspberrypi_clk_data *data =
233 		container_of(hw, struct raspberrypi_clk_data, hw);
234 	struct raspberrypi_clk_variant *variant = data->variant;
235 
236 	/*
237 	 * The firmware will do the rounding but that isn't part of
238 	 * the interface with the firmware, so we just do our best
239 	 * here.
240 	 */
241 
242 	req->rate = clamp(req->rate, req->min_rate, req->max_rate);
243 
244 	/*
245 	 * We want to aggressively reduce the clock rate here, so let's
246 	 * just ignore the requested rate and return the bare minimum
247 	 * rate we can get away with.
248 	 */
249 	if (variant->minimize && req->min_rate > 0)
250 		req->rate = req->min_rate;
251 
252 	return 0;
253 }
254 
255 static const struct clk_ops raspberrypi_firmware_clk_ops = {
256 	.is_prepared	= raspberrypi_fw_is_prepared,
257 	.recalc_rate	= raspberrypi_fw_get_rate,
258 	.determine_rate	= raspberrypi_fw_dumb_determine_rate,
259 	.set_rate	= raspberrypi_fw_set_rate,
260 };
261 
262 static struct clk_hw *raspberrypi_clk_register(struct raspberrypi_clk *rpi,
263 					       unsigned int parent,
264 					       unsigned int id,
265 					       struct raspberrypi_clk_variant *variant)
266 {
267 	struct raspberrypi_clk_data *data;
268 	struct clk_init_data init = {};
269 	u32 min_rate, max_rate;
270 	int ret;
271 
272 	data = devm_kzalloc(rpi->dev, sizeof(*data), GFP_KERNEL);
273 	if (!data)
274 		return ERR_PTR(-ENOMEM);
275 	data->rpi = rpi;
276 	data->id = id;
277 	data->variant = variant;
278 
279 	init.name = devm_kasprintf(rpi->dev, GFP_KERNEL,
280 				   "fw-clk-%s",
281 				   rpi_firmware_clk_names[id]);
282 	init.ops = &raspberrypi_firmware_clk_ops;
283 	init.flags = CLK_GET_RATE_NOCACHE;
284 
285 	data->hw.init = &init;
286 
287 	ret = raspberrypi_clock_property(rpi->firmware, data,
288 					 RPI_FIRMWARE_GET_MIN_CLOCK_RATE,
289 					 &min_rate);
290 	if (ret) {
291 		dev_err(rpi->dev, "Failed to get clock %d min freq: %d",
292 			id, ret);
293 		return ERR_PTR(ret);
294 	}
295 
296 	ret = raspberrypi_clock_property(rpi->firmware, data,
297 					 RPI_FIRMWARE_GET_MAX_CLOCK_RATE,
298 					 &max_rate);
299 	if (ret) {
300 		dev_err(rpi->dev, "Failed to get clock %d max freq: %d\n",
301 			id, ret);
302 		return ERR_PTR(ret);
303 	}
304 
305 	ret = devm_clk_hw_register(rpi->dev, &data->hw);
306 	if (ret)
307 		return ERR_PTR(ret);
308 
309 	clk_hw_set_rate_range(&data->hw, min_rate, max_rate);
310 
311 	if (variant->clkdev) {
312 		ret = devm_clk_hw_register_clkdev(rpi->dev, &data->hw,
313 						  NULL, variant->clkdev);
314 		if (ret) {
315 			dev_err(rpi->dev, "Failed to initialize clkdev\n");
316 			return ERR_PTR(ret);
317 		}
318 	}
319 
320 	if (variant->min_rate) {
321 		unsigned long rate;
322 
323 		clk_hw_set_rate_range(&data->hw, variant->min_rate, max_rate);
324 
325 		rate = raspberrypi_fw_get_rate(&data->hw, 0);
326 		if (rate < variant->min_rate) {
327 			ret = raspberrypi_fw_set_rate(&data->hw, variant->min_rate, 0);
328 			if (ret)
329 				return ERR_PTR(ret);
330 		}
331 	}
332 
333 	return &data->hw;
334 }
335 
336 struct rpi_firmware_get_clocks_response {
337 	u32 parent;
338 	u32 id;
339 };
340 
341 static int raspberrypi_discover_clocks(struct raspberrypi_clk *rpi,
342 				       struct clk_hw_onecell_data *data)
343 {
344 	struct rpi_firmware_get_clocks_response *clks;
345 	int ret;
346 
347 	clks = devm_kcalloc(rpi->dev,
348 			    RPI_FIRMWARE_NUM_CLK_ID, sizeof(*clks),
349 			    GFP_KERNEL);
350 	if (!clks)
351 		return -ENOMEM;
352 
353 	ret = rpi_firmware_property(rpi->firmware, RPI_FIRMWARE_GET_CLOCKS,
354 				    clks,
355 				    sizeof(*clks) * RPI_FIRMWARE_NUM_CLK_ID);
356 	if (ret)
357 		return ret;
358 
359 	while (clks->id) {
360 		struct raspberrypi_clk_variant *variant;
361 
362 		if (clks->id > RPI_FIRMWARE_NUM_CLK_ID) {
363 			dev_err(rpi->dev, "Unknown clock id: %u", clks->id);
364 			return -EINVAL;
365 		}
366 
367 		variant = &raspberrypi_clk_variants[clks->id];
368 		if (variant->export) {
369 			struct clk_hw *hw;
370 
371 			hw = raspberrypi_clk_register(rpi, clks->parent,
372 						      clks->id, variant);
373 			if (IS_ERR(hw))
374 				return PTR_ERR(hw);
375 
376 			data->hws[clks->id] = hw;
377 			data->num = clks->id + 1;
378 		}
379 
380 		clks++;
381 	}
382 
383 	return 0;
384 }
385 
386 static int raspberrypi_clk_probe(struct platform_device *pdev)
387 {
388 	struct clk_hw_onecell_data *clk_data;
389 	struct device_node *firmware_node;
390 	struct device *dev = &pdev->dev;
391 	struct rpi_firmware *firmware;
392 	struct raspberrypi_clk *rpi;
393 	int ret;
394 
395 	/*
396 	 * We can be probed either through the an old-fashioned
397 	 * platform device registration or through a DT node that is a
398 	 * child of the firmware node. Handle both cases.
399 	 */
400 	if (dev->of_node)
401 		firmware_node = of_get_parent(dev->of_node);
402 	else
403 		firmware_node = of_find_compatible_node(NULL, NULL,
404 							"raspberrypi,bcm2835-firmware");
405 	if (!firmware_node) {
406 		dev_err(dev, "Missing firmware node\n");
407 		return -ENOENT;
408 	}
409 
410 	firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
411 	of_node_put(firmware_node);
412 	if (!firmware)
413 		return -EPROBE_DEFER;
414 
415 	rpi = devm_kzalloc(dev, sizeof(*rpi), GFP_KERNEL);
416 	if (!rpi)
417 		return -ENOMEM;
418 
419 	rpi->dev = dev;
420 	rpi->firmware = firmware;
421 	platform_set_drvdata(pdev, rpi);
422 
423 	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws,
424 						 RPI_FIRMWARE_NUM_CLK_ID),
425 				GFP_KERNEL);
426 	if (!clk_data)
427 		return -ENOMEM;
428 
429 	ret = raspberrypi_discover_clocks(rpi, clk_data);
430 	if (ret)
431 		return ret;
432 
433 	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get,
434 					  clk_data);
435 	if (ret)
436 		return ret;
437 
438 	rpi->cpufreq = platform_device_register_data(dev, "raspberrypi-cpufreq",
439 						     -1, NULL, 0);
440 
441 	return 0;
442 }
443 
444 static int raspberrypi_clk_remove(struct platform_device *pdev)
445 {
446 	struct raspberrypi_clk *rpi = platform_get_drvdata(pdev);
447 
448 	platform_device_unregister(rpi->cpufreq);
449 
450 	return 0;
451 }
452 
453 static const struct of_device_id raspberrypi_clk_match[] = {
454 	{ .compatible = "raspberrypi,firmware-clocks" },
455 	{ },
456 };
457 MODULE_DEVICE_TABLE(of, raspberrypi_clk_match);
458 
459 static struct platform_driver raspberrypi_clk_driver = {
460 	.driver = {
461 		.name = "raspberrypi-clk",
462 		.of_match_table = raspberrypi_clk_match,
463 	},
464 	.probe          = raspberrypi_clk_probe,
465 	.remove		= raspberrypi_clk_remove,
466 };
467 module_platform_driver(raspberrypi_clk_driver);
468 
469 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
470 MODULE_DESCRIPTION("Raspberry Pi firmware clock driver");
471 MODULE_LICENSE("GPL");
472 MODULE_ALIAS("platform:raspberrypi-clk");
473