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