1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2015 Free Electrons
4  * Copyright (C) 2015 NextThing Co
5  *
6  * Maxime Ripard <maxime.ripard@free-electrons.com>
7  */
8 
9 #include <linux/component.h>
10 #include <linux/list.h>
11 #include <linux/module.h>
12 #include <linux/of_device.h>
13 #include <linux/of_graph.h>
14 #include <linux/platform_device.h>
15 #include <linux/reset.h>
16 
17 #include <drm/drm_atomic.h>
18 #include <drm/drm_atomic_helper.h>
19 #include <drm/drm_crtc.h>
20 #include <drm/drm_fb_cma_helper.h>
21 #include <drm/drm_fourcc.h>
22 #include <drm/drm_gem_cma_helper.h>
23 #include <drm/drm_plane_helper.h>
24 #include <drm/drm_probe_helper.h>
25 
26 #include "sun4i_backend.h"
27 #include "sun4i_drv.h"
28 #include "sun4i_frontend.h"
29 #include "sun4i_layer.h"
30 #include "sunxi_engine.h"
31 
32 struct sun4i_backend_quirks {
33 	/* backend <-> TCON muxing selection done in backend */
34 	bool needs_output_muxing;
35 
36 	/* alpha at the lowest z position is not always supported */
37 	bool supports_lowest_plane_alpha;
38 };
39 
40 static const u32 sunxi_rgb2yuv_coef[12] = {
41 	0x00000107, 0x00000204, 0x00000064, 0x00000108,
42 	0x00003f69, 0x00003ed6, 0x000001c1, 0x00000808,
43 	0x000001c1, 0x00003e88, 0x00003fb8, 0x00000808
44 };
45 
46 static void sun4i_backend_apply_color_correction(struct sunxi_engine *engine)
47 {
48 	int i;
49 
50 	DRM_DEBUG_DRIVER("Applying RGB to YUV color correction\n");
51 
52 	/* Set color correction */
53 	regmap_write(engine->regs, SUN4I_BACKEND_OCCTL_REG,
54 		     SUN4I_BACKEND_OCCTL_ENABLE);
55 
56 	for (i = 0; i < 12; i++)
57 		regmap_write(engine->regs, SUN4I_BACKEND_OCRCOEF_REG(i),
58 			     sunxi_rgb2yuv_coef[i]);
59 }
60 
61 static void sun4i_backend_disable_color_correction(struct sunxi_engine *engine)
62 {
63 	DRM_DEBUG_DRIVER("Disabling color correction\n");
64 
65 	/* Disable color correction */
66 	regmap_update_bits(engine->regs, SUN4I_BACKEND_OCCTL_REG,
67 			   SUN4I_BACKEND_OCCTL_ENABLE, 0);
68 }
69 
70 static void sun4i_backend_commit(struct sunxi_engine *engine)
71 {
72 	DRM_DEBUG_DRIVER("Committing changes\n");
73 
74 	regmap_write(engine->regs, SUN4I_BACKEND_REGBUFFCTL_REG,
75 		     SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS |
76 		     SUN4I_BACKEND_REGBUFFCTL_LOADCTL);
77 }
78 
79 void sun4i_backend_layer_enable(struct sun4i_backend *backend,
80 				int layer, bool enable)
81 {
82 	u32 val;
83 
84 	DRM_DEBUG_DRIVER("%sabling layer %d\n", enable ? "En" : "Dis",
85 			 layer);
86 
87 	if (enable)
88 		val = SUN4I_BACKEND_MODCTL_LAY_EN(layer);
89 	else
90 		val = 0;
91 
92 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
93 			   SUN4I_BACKEND_MODCTL_LAY_EN(layer), val);
94 }
95 
96 static int sun4i_backend_drm_format_to_layer(u32 format, u32 *mode)
97 {
98 	switch (format) {
99 	case DRM_FORMAT_ARGB8888:
100 		*mode = SUN4I_BACKEND_LAY_FBFMT_ARGB8888;
101 		break;
102 
103 	case DRM_FORMAT_ARGB4444:
104 		*mode = SUN4I_BACKEND_LAY_FBFMT_ARGB4444;
105 		break;
106 
107 	case DRM_FORMAT_ARGB1555:
108 		*mode = SUN4I_BACKEND_LAY_FBFMT_ARGB1555;
109 		break;
110 
111 	case DRM_FORMAT_RGBA5551:
112 		*mode = SUN4I_BACKEND_LAY_FBFMT_RGBA5551;
113 		break;
114 
115 	case DRM_FORMAT_RGBA4444:
116 		*mode = SUN4I_BACKEND_LAY_FBFMT_RGBA4444;
117 		break;
118 
119 	case DRM_FORMAT_XRGB8888:
120 		*mode = SUN4I_BACKEND_LAY_FBFMT_XRGB8888;
121 		break;
122 
123 	case DRM_FORMAT_RGB888:
124 		*mode = SUN4I_BACKEND_LAY_FBFMT_RGB888;
125 		break;
126 
127 	case DRM_FORMAT_RGB565:
128 		*mode = SUN4I_BACKEND_LAY_FBFMT_RGB565;
129 		break;
130 
131 	default:
132 		return -EINVAL;
133 	}
134 
135 	return 0;
136 }
137 
138 static const uint32_t sun4i_backend_formats[] = {
139 	DRM_FORMAT_ARGB1555,
140 	DRM_FORMAT_ARGB4444,
141 	DRM_FORMAT_ARGB8888,
142 	DRM_FORMAT_RGB565,
143 	DRM_FORMAT_RGB888,
144 	DRM_FORMAT_RGBA4444,
145 	DRM_FORMAT_RGBA5551,
146 	DRM_FORMAT_UYVY,
147 	DRM_FORMAT_VYUY,
148 	DRM_FORMAT_XRGB8888,
149 	DRM_FORMAT_YUYV,
150 	DRM_FORMAT_YVYU,
151 };
152 
153 bool sun4i_backend_format_is_supported(uint32_t fmt, uint64_t modifier)
154 {
155 	unsigned int i;
156 
157 	if (modifier != DRM_FORMAT_MOD_LINEAR)
158 		return false;
159 
160 	for (i = 0; i < ARRAY_SIZE(sun4i_backend_formats); i++)
161 		if (sun4i_backend_formats[i] == fmt)
162 			return true;
163 
164 	return false;
165 }
166 
167 int sun4i_backend_update_layer_coord(struct sun4i_backend *backend,
168 				     int layer, struct drm_plane *plane)
169 {
170 	struct drm_plane_state *state = plane->state;
171 
172 	DRM_DEBUG_DRIVER("Updating layer %d\n", layer);
173 
174 	if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
175 		DRM_DEBUG_DRIVER("Primary layer, updating global size W: %u H: %u\n",
176 				 state->crtc_w, state->crtc_h);
177 		regmap_write(backend->engine.regs, SUN4I_BACKEND_DISSIZE_REG,
178 			     SUN4I_BACKEND_DISSIZE(state->crtc_w,
179 						   state->crtc_h));
180 	}
181 
182 	/* Set height and width */
183 	DRM_DEBUG_DRIVER("Layer size W: %u H: %u\n",
184 			 state->crtc_w, state->crtc_h);
185 	regmap_write(backend->engine.regs, SUN4I_BACKEND_LAYSIZE_REG(layer),
186 		     SUN4I_BACKEND_LAYSIZE(state->crtc_w,
187 					   state->crtc_h));
188 
189 	/* Set base coordinates */
190 	DRM_DEBUG_DRIVER("Layer coordinates X: %d Y: %d\n",
191 			 state->crtc_x, state->crtc_y);
192 	regmap_write(backend->engine.regs, SUN4I_BACKEND_LAYCOOR_REG(layer),
193 		     SUN4I_BACKEND_LAYCOOR(state->crtc_x,
194 					   state->crtc_y));
195 
196 	return 0;
197 }
198 
199 static int sun4i_backend_update_yuv_format(struct sun4i_backend *backend,
200 					   int layer, struct drm_plane *plane)
201 {
202 	struct drm_plane_state *state = plane->state;
203 	struct drm_framebuffer *fb = state->fb;
204 	const struct drm_format_info *format = fb->format;
205 	const uint32_t fmt = format->format;
206 	u32 val = SUN4I_BACKEND_IYUVCTL_EN;
207 	int i;
208 
209 	for (i = 0; i < ARRAY_SIZE(sunxi_bt601_yuv2rgb_coef); i++)
210 		regmap_write(backend->engine.regs,
211 			     SUN4I_BACKEND_YGCOEF_REG(i),
212 			     sunxi_bt601_yuv2rgb_coef[i]);
213 
214 	/*
215 	 * We should do that only for a single plane, but the
216 	 * framebuffer's atomic_check has our back on this.
217 	 */
218 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
219 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN,
220 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN);
221 
222 	/* TODO: Add support for the multi-planar YUV formats */
223 	if (drm_format_info_is_yuv_packed(format) &&
224 	    drm_format_info_is_yuv_sampling_422(format))
225 		val |= SUN4I_BACKEND_IYUVCTL_FBFMT_PACKED_YUV422;
226 	else
227 		DRM_DEBUG_DRIVER("Unsupported YUV format (0x%x)\n", fmt);
228 
229 	/*
230 	 * Allwinner seems to list the pixel sequence from right to left, while
231 	 * DRM lists it from left to right.
232 	 */
233 	switch (fmt) {
234 	case DRM_FORMAT_YUYV:
235 		val |= SUN4I_BACKEND_IYUVCTL_FBPS_VYUY;
236 		break;
237 	case DRM_FORMAT_YVYU:
238 		val |= SUN4I_BACKEND_IYUVCTL_FBPS_UYVY;
239 		break;
240 	case DRM_FORMAT_UYVY:
241 		val |= SUN4I_BACKEND_IYUVCTL_FBPS_YVYU;
242 		break;
243 	case DRM_FORMAT_VYUY:
244 		val |= SUN4I_BACKEND_IYUVCTL_FBPS_YUYV;
245 		break;
246 	default:
247 		DRM_DEBUG_DRIVER("Unsupported YUV pixel sequence (0x%x)\n",
248 				 fmt);
249 	}
250 
251 	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVCTL_REG, val);
252 
253 	return 0;
254 }
255 
256 int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
257 				       int layer, struct drm_plane *plane)
258 {
259 	struct drm_plane_state *state = plane->state;
260 	struct drm_framebuffer *fb = state->fb;
261 	bool interlaced = false;
262 	u32 val;
263 	int ret;
264 
265 	/* Clear the YUV mode */
266 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
267 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN, 0);
268 
269 	if (plane->state->crtc)
270 		interlaced = plane->state->crtc->state->adjusted_mode.flags
271 			& DRM_MODE_FLAG_INTERLACE;
272 
273 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
274 			   SUN4I_BACKEND_MODCTL_ITLMOD_EN,
275 			   interlaced ? SUN4I_BACKEND_MODCTL_ITLMOD_EN : 0);
276 
277 	DRM_DEBUG_DRIVER("Switching display backend interlaced mode %s\n",
278 			 interlaced ? "on" : "off");
279 
280 	val = SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA(state->alpha >> 8);
281 	if (state->alpha != DRM_BLEND_ALPHA_OPAQUE)
282 		val |= SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN;
283 	regmap_update_bits(backend->engine.regs,
284 			   SUN4I_BACKEND_ATTCTL_REG0(layer),
285 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_MASK |
286 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN,
287 			   val);
288 
289 	if (fb->format->is_yuv)
290 		return sun4i_backend_update_yuv_format(backend, layer, plane);
291 
292 	ret = sun4i_backend_drm_format_to_layer(fb->format->format, &val);
293 	if (ret) {
294 		DRM_DEBUG_DRIVER("Invalid format\n");
295 		return ret;
296 	}
297 
298 	regmap_update_bits(backend->engine.regs,
299 			   SUN4I_BACKEND_ATTCTL_REG1(layer),
300 			   SUN4I_BACKEND_ATTCTL_REG1_LAY_FBFMT, val);
301 
302 	return 0;
303 }
304 
305 int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
306 					int layer, uint32_t fmt)
307 {
308 	u32 val;
309 	int ret;
310 
311 	ret = sun4i_backend_drm_format_to_layer(fmt, &val);
312 	if (ret) {
313 		DRM_DEBUG_DRIVER("Invalid format\n");
314 		return ret;
315 	}
316 
317 	regmap_update_bits(backend->engine.regs,
318 			   SUN4I_BACKEND_ATTCTL_REG0(layer),
319 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN,
320 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN);
321 
322 	regmap_update_bits(backend->engine.regs,
323 			   SUN4I_BACKEND_ATTCTL_REG1(layer),
324 			   SUN4I_BACKEND_ATTCTL_REG1_LAY_FBFMT, val);
325 
326 	return 0;
327 }
328 
329 static int sun4i_backend_update_yuv_buffer(struct sun4i_backend *backend,
330 					   struct drm_framebuffer *fb,
331 					   dma_addr_t paddr)
332 {
333 	/* TODO: Add support for the multi-planar YUV formats */
334 	DRM_DEBUG_DRIVER("Setting packed YUV buffer address to %pad\n", &paddr);
335 	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVADD_REG(0), paddr);
336 
337 	DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
338 	regmap_write(backend->engine.regs, SUN4I_BACKEND_IYUVLINEWIDTH_REG(0),
339 		     fb->pitches[0] * 8);
340 
341 	return 0;
342 }
343 
344 int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend,
345 				      int layer, struct drm_plane *plane)
346 {
347 	struct drm_plane_state *state = plane->state;
348 	struct drm_framebuffer *fb = state->fb;
349 	u32 lo_paddr, hi_paddr;
350 	dma_addr_t paddr;
351 
352 	/* Set the line width */
353 	DRM_DEBUG_DRIVER("Layer line width: %d bits\n", fb->pitches[0] * 8);
354 	regmap_write(backend->engine.regs,
355 		     SUN4I_BACKEND_LAYLINEWIDTH_REG(layer),
356 		     fb->pitches[0] * 8);
357 
358 	/* Get the start of the displayed memory */
359 	paddr = drm_fb_cma_get_gem_addr(fb, state, 0);
360 	DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr);
361 
362 	if (fb->format->is_yuv)
363 		return sun4i_backend_update_yuv_buffer(backend, fb, paddr);
364 
365 	/* Write the 32 lower bits of the address (in bits) */
366 	lo_paddr = paddr << 3;
367 	DRM_DEBUG_DRIVER("Setting address lower bits to 0x%x\n", lo_paddr);
368 	regmap_write(backend->engine.regs,
369 		     SUN4I_BACKEND_LAYFB_L32ADD_REG(layer),
370 		     lo_paddr);
371 
372 	/* And the upper bits */
373 	hi_paddr = paddr >> 29;
374 	DRM_DEBUG_DRIVER("Setting address high bits to 0x%x\n", hi_paddr);
375 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_LAYFB_H4ADD_REG,
376 			   SUN4I_BACKEND_LAYFB_H4ADD_MSK(layer),
377 			   SUN4I_BACKEND_LAYFB_H4ADD(layer, hi_paddr));
378 
379 	return 0;
380 }
381 
382 int sun4i_backend_update_layer_zpos(struct sun4i_backend *backend, int layer,
383 				    struct drm_plane *plane)
384 {
385 	struct drm_plane_state *state = plane->state;
386 	struct sun4i_layer_state *p_state = state_to_sun4i_layer_state(state);
387 	unsigned int priority = state->normalized_zpos;
388 	unsigned int pipe = p_state->pipe;
389 
390 	DRM_DEBUG_DRIVER("Setting layer %d's priority to %d and pipe %d\n",
391 			 layer, priority, pipe);
392 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
393 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL_MASK |
394 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK,
395 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(p_state->pipe) |
396 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(priority));
397 
398 	return 0;
399 }
400 
401 void sun4i_backend_cleanup_layer(struct sun4i_backend *backend,
402 				 int layer)
403 {
404 	regmap_update_bits(backend->engine.regs,
405 			   SUN4I_BACKEND_ATTCTL_REG0(layer),
406 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN |
407 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN, 0);
408 }
409 
410 static bool sun4i_backend_plane_uses_scaler(struct drm_plane_state *state)
411 {
412 	u16 src_h = state->src_h >> 16;
413 	u16 src_w = state->src_w >> 16;
414 
415 	DRM_DEBUG_DRIVER("Input size %dx%d, output size %dx%d\n",
416 			 src_w, src_h, state->crtc_w, state->crtc_h);
417 
418 	if ((state->crtc_h != src_h) || (state->crtc_w != src_w))
419 		return true;
420 
421 	return false;
422 }
423 
424 static bool sun4i_backend_plane_uses_frontend(struct drm_plane_state *state)
425 {
426 	struct sun4i_layer *layer = plane_to_sun4i_layer(state->plane);
427 	struct sun4i_backend *backend = layer->backend;
428 	uint32_t format = state->fb->format->format;
429 	uint64_t modifier = state->fb->modifier;
430 
431 	if (IS_ERR(backend->frontend))
432 		return false;
433 
434 	if (!sun4i_frontend_format_is_supported(format, modifier))
435 		return false;
436 
437 	if (!sun4i_backend_format_is_supported(format, modifier))
438 		return true;
439 
440 	/*
441 	 * TODO: The backend alone allows 2x and 4x integer scaling, including
442 	 * support for an alpha component (which the frontend doesn't support).
443 	 * Use the backend directly instead of the frontend in this case, with
444 	 * another test to return false.
445 	 */
446 
447 	if (sun4i_backend_plane_uses_scaler(state))
448 		return true;
449 
450 	/*
451 	 * Here the format is supported by both the frontend and the backend
452 	 * and no frontend scaling is required, so use the backend directly.
453 	 */
454 	return false;
455 }
456 
457 static bool sun4i_backend_plane_is_supported(struct drm_plane_state *state,
458 					     bool *uses_frontend)
459 {
460 	if (sun4i_backend_plane_uses_frontend(state)) {
461 		*uses_frontend = true;
462 		return true;
463 	}
464 
465 	*uses_frontend = false;
466 
467 	/* Scaling is not supported without the frontend. */
468 	if (sun4i_backend_plane_uses_scaler(state))
469 		return false;
470 
471 	return true;
472 }
473 
474 static void sun4i_backend_atomic_begin(struct sunxi_engine *engine,
475 				       struct drm_crtc_state *old_state)
476 {
477 	u32 val;
478 
479 	WARN_ON(regmap_read_poll_timeout(engine->regs,
480 					 SUN4I_BACKEND_REGBUFFCTL_REG,
481 					 val, !(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL),
482 					 100, 50000));
483 }
484 
485 static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
486 				      struct drm_crtc_state *crtc_state)
487 {
488 	struct drm_plane_state *plane_states[SUN4I_BACKEND_NUM_LAYERS] = { 0 };
489 	struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
490 	struct drm_atomic_state *state = crtc_state->state;
491 	struct drm_device *drm = state->dev;
492 	struct drm_plane *plane;
493 	unsigned int num_planes = 0;
494 	unsigned int num_alpha_planes = 0;
495 	unsigned int num_frontend_planes = 0;
496 	unsigned int num_alpha_planes_max = 1;
497 	unsigned int num_yuv_planes = 0;
498 	unsigned int current_pipe = 0;
499 	unsigned int i;
500 
501 	DRM_DEBUG_DRIVER("Starting checking our planes\n");
502 
503 	if (!crtc_state->planes_changed)
504 		return 0;
505 
506 	drm_for_each_plane_mask(plane, drm, crtc_state->plane_mask) {
507 		struct drm_plane_state *plane_state =
508 			drm_atomic_get_plane_state(state, plane);
509 		struct sun4i_layer_state *layer_state =
510 			state_to_sun4i_layer_state(plane_state);
511 		struct drm_framebuffer *fb = plane_state->fb;
512 		struct drm_format_name_buf format_name;
513 
514 		if (!sun4i_backend_plane_is_supported(plane_state,
515 						      &layer_state->uses_frontend))
516 			return -EINVAL;
517 
518 		if (layer_state->uses_frontend) {
519 			DRM_DEBUG_DRIVER("Using the frontend for plane %d\n",
520 					 plane->index);
521 			num_frontend_planes++;
522 		} else {
523 			if (fb->format->is_yuv) {
524 				DRM_DEBUG_DRIVER("Plane FB format is YUV\n");
525 				num_yuv_planes++;
526 			}
527 		}
528 
529 		DRM_DEBUG_DRIVER("Plane FB format is %s\n",
530 				 drm_get_format_name(fb->format->format,
531 						     &format_name));
532 		if (fb->format->has_alpha || (plane_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
533 			num_alpha_planes++;
534 
535 		DRM_DEBUG_DRIVER("Plane zpos is %d\n",
536 				 plane_state->normalized_zpos);
537 
538 		/* Sort our planes by Zpos */
539 		plane_states[plane_state->normalized_zpos] = plane_state;
540 
541 		num_planes++;
542 	}
543 
544 	/* All our planes were disabled, bail out */
545 	if (!num_planes)
546 		return 0;
547 
548 	/*
549 	 * The hardware is a bit unusual here.
550 	 *
551 	 * Even though it supports 4 layers, it does the composition
552 	 * in two separate steps.
553 	 *
554 	 * The first one is assigning a layer to one of its two
555 	 * pipes. If more that 1 layer is assigned to the same pipe,
556 	 * and if pixels overlaps, the pipe will take the pixel from
557 	 * the layer with the highest priority.
558 	 *
559 	 * The second step is the actual alpha blending, that takes
560 	 * the two pipes as input, and uses the potential alpha
561 	 * component to do the transparency between the two.
562 	 *
563 	 * This two-step scenario makes us unable to guarantee a
564 	 * robust alpha blending between the 4 layers in all
565 	 * situations, since this means that we need to have one layer
566 	 * with alpha at the lowest position of our two pipes.
567 	 *
568 	 * However, we cannot even do that on every platform, since
569 	 * the hardware has a bug where the lowest plane of the lowest
570 	 * pipe (pipe 0, priority 0), if it has any alpha, will
571 	 * discard the pixel data entirely and just display the pixels
572 	 * in the background color (black by default).
573 	 *
574 	 * This means that on the affected platforms, we effectively
575 	 * have only three valid configurations with alpha, all of
576 	 * them with the alpha being on pipe1 with the lowest
577 	 * position, which can be 1, 2 or 3 depending on the number of
578 	 * planes and their zpos.
579 	 */
580 
581 	/* For platforms that are not affected by the issue described above. */
582 	if (backend->quirks->supports_lowest_plane_alpha)
583 		num_alpha_planes_max++;
584 
585 	if (num_alpha_planes > num_alpha_planes_max) {
586 		DRM_DEBUG_DRIVER("Too many planes with alpha, rejecting...\n");
587 		return -EINVAL;
588 	}
589 
590 	/* We can't have an alpha plane at the lowest position */
591 	if (!backend->quirks->supports_lowest_plane_alpha &&
592 	    (plane_states[0]->alpha != DRM_BLEND_ALPHA_OPAQUE))
593 		return -EINVAL;
594 
595 	for (i = 1; i < num_planes; i++) {
596 		struct drm_plane_state *p_state = plane_states[i];
597 		struct drm_framebuffer *fb = p_state->fb;
598 		struct sun4i_layer_state *s_state = state_to_sun4i_layer_state(p_state);
599 
600 		/*
601 		 * The only alpha position is the lowest plane of the
602 		 * second pipe.
603 		 */
604 		if (fb->format->has_alpha || (p_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
605 			current_pipe++;
606 
607 		s_state->pipe = current_pipe;
608 	}
609 
610 	/* We can only have a single YUV plane at a time */
611 	if (num_yuv_planes > SUN4I_BACKEND_NUM_YUV_PLANES) {
612 		DRM_DEBUG_DRIVER("Too many planes with YUV, rejecting...\n");
613 		return -EINVAL;
614 	}
615 
616 	if (num_frontend_planes > SUN4I_BACKEND_NUM_FRONTEND_LAYERS) {
617 		DRM_DEBUG_DRIVER("Too many planes going through the frontend, rejecting\n");
618 		return -EINVAL;
619 	}
620 
621 	DRM_DEBUG_DRIVER("State valid with %u planes, %u alpha, %u video, %u YUV\n",
622 			 num_planes, num_alpha_planes, num_frontend_planes,
623 			 num_yuv_planes);
624 
625 	return 0;
626 }
627 
628 static void sun4i_backend_vblank_quirk(struct sunxi_engine *engine)
629 {
630 	struct sun4i_backend *backend = engine_to_sun4i_backend(engine);
631 	struct sun4i_frontend *frontend = backend->frontend;
632 
633 	if (!frontend)
634 		return;
635 
636 	/*
637 	 * In a teardown scenario with the frontend involved, we have
638 	 * to keep the frontend enabled until the next vblank, and
639 	 * only then disable it.
640 	 *
641 	 * This is due to the fact that the backend will not take into
642 	 * account the new configuration (with the plane that used to
643 	 * be fed by the frontend now disabled) until we write to the
644 	 * commit bit and the hardware fetches the new configuration
645 	 * during the next vblank.
646 	 *
647 	 * So we keep the frontend around in order to prevent any
648 	 * visual artifacts.
649 	 */
650 	spin_lock(&backend->frontend_lock);
651 	if (backend->frontend_teardown) {
652 		sun4i_frontend_exit(frontend);
653 		backend->frontend_teardown = false;
654 	}
655 	spin_unlock(&backend->frontend_lock);
656 };
657 
658 static int sun4i_backend_init_sat(struct device *dev) {
659 	struct sun4i_backend *backend = dev_get_drvdata(dev);
660 	int ret;
661 
662 	backend->sat_reset = devm_reset_control_get(dev, "sat");
663 	if (IS_ERR(backend->sat_reset)) {
664 		dev_err(dev, "Couldn't get the SAT reset line\n");
665 		return PTR_ERR(backend->sat_reset);
666 	}
667 
668 	ret = reset_control_deassert(backend->sat_reset);
669 	if (ret) {
670 		dev_err(dev, "Couldn't deassert the SAT reset line\n");
671 		return ret;
672 	}
673 
674 	backend->sat_clk = devm_clk_get(dev, "sat");
675 	if (IS_ERR(backend->sat_clk)) {
676 		dev_err(dev, "Couldn't get our SAT clock\n");
677 		ret = PTR_ERR(backend->sat_clk);
678 		goto err_assert_reset;
679 	}
680 
681 	ret = clk_prepare_enable(backend->sat_clk);
682 	if (ret) {
683 		dev_err(dev, "Couldn't enable the SAT clock\n");
684 		return ret;
685 	}
686 
687 	return 0;
688 
689 err_assert_reset:
690 	reset_control_assert(backend->sat_reset);
691 	return ret;
692 }
693 
694 static int sun4i_backend_free_sat(struct device *dev) {
695 	struct sun4i_backend *backend = dev_get_drvdata(dev);
696 
697 	clk_disable_unprepare(backend->sat_clk);
698 	reset_control_assert(backend->sat_reset);
699 
700 	return 0;
701 }
702 
703 /*
704  * The display backend can take video output from the display frontend, or
705  * the display enhancement unit on the A80, as input for one it its layers.
706  * This relationship within the display pipeline is encoded in the device
707  * tree with of_graph, and we use it here to figure out which backend, if
708  * there are 2 or more, we are currently probing. The number would be in
709  * the "reg" property of the upstream output port endpoint.
710  */
711 static int sun4i_backend_of_get_id(struct device_node *node)
712 {
713 	struct device_node *ep, *remote;
714 	struct of_endpoint of_ep;
715 
716 	/* Input port is 0, and we want the first endpoint. */
717 	ep = of_graph_get_endpoint_by_regs(node, 0, -1);
718 	if (!ep)
719 		return -EINVAL;
720 
721 	remote = of_graph_get_remote_endpoint(ep);
722 	of_node_put(ep);
723 	if (!remote)
724 		return -EINVAL;
725 
726 	of_graph_parse_endpoint(remote, &of_ep);
727 	of_node_put(remote);
728 	return of_ep.id;
729 }
730 
731 /* TODO: This needs to take multiple pipelines into account */
732 static struct sun4i_frontend *sun4i_backend_find_frontend(struct sun4i_drv *drv,
733 							  struct device_node *node)
734 {
735 	struct device_node *port, *ep, *remote;
736 	struct sun4i_frontend *frontend;
737 
738 	port = of_graph_get_port_by_id(node, 0);
739 	if (!port)
740 		return ERR_PTR(-EINVAL);
741 
742 	for_each_available_child_of_node(port, ep) {
743 		remote = of_graph_get_remote_port_parent(ep);
744 		if (!remote)
745 			continue;
746 		of_node_put(remote);
747 
748 		/* does this node match any registered engines? */
749 		list_for_each_entry(frontend, &drv->frontend_list, list) {
750 			if (remote == frontend->node) {
751 				of_node_put(port);
752 				of_node_put(ep);
753 				return frontend;
754 			}
755 		}
756 	}
757 	of_node_put(port);
758 	return ERR_PTR(-EINVAL);
759 }
760 
761 static const struct sunxi_engine_ops sun4i_backend_engine_ops = {
762 	.atomic_begin			= sun4i_backend_atomic_begin,
763 	.atomic_check			= sun4i_backend_atomic_check,
764 	.commit				= sun4i_backend_commit,
765 	.layers_init			= sun4i_layers_init,
766 	.apply_color_correction		= sun4i_backend_apply_color_correction,
767 	.disable_color_correction	= sun4i_backend_disable_color_correction,
768 	.vblank_quirk			= sun4i_backend_vblank_quirk,
769 };
770 
771 static struct regmap_config sun4i_backend_regmap_config = {
772 	.reg_bits	= 32,
773 	.val_bits	= 32,
774 	.reg_stride	= 4,
775 	.max_register	= 0x5800,
776 };
777 
778 static int sun4i_backend_bind(struct device *dev, struct device *master,
779 			      void *data)
780 {
781 	struct platform_device *pdev = to_platform_device(dev);
782 	struct drm_device *drm = data;
783 	struct sun4i_drv *drv = drm->dev_private;
784 	struct sun4i_backend *backend;
785 	const struct sun4i_backend_quirks *quirks;
786 	struct resource *res;
787 	void __iomem *regs;
788 	int i, ret;
789 
790 	backend = devm_kzalloc(dev, sizeof(*backend), GFP_KERNEL);
791 	if (!backend)
792 		return -ENOMEM;
793 	dev_set_drvdata(dev, backend);
794 	spin_lock_init(&backend->frontend_lock);
795 
796 	if (of_find_property(dev->of_node, "interconnects", NULL)) {
797 		/*
798 		 * This assume we have the same DMA constraints for all our the
799 		 * devices in our pipeline (all the backends, but also the
800 		 * frontends). This sounds bad, but it has always been the case
801 		 * for us, and DRM doesn't do per-device allocation either, so
802 		 * we would need to fix DRM first...
803 		 */
804 		ret = of_dma_configure(drm->dev, dev->of_node, true);
805 		if (ret)
806 			return ret;
807 	} else {
808 		/*
809 		 * If we don't have the interconnect property, most likely
810 		 * because of an old DT, we need to set the DMA offset by hand
811 		 * on our device since the RAM mapping is at 0 for the DMA bus,
812 		 * unlike the CPU.
813 		 */
814 		drm->dev->dma_pfn_offset = PHYS_PFN_OFFSET;
815 	}
816 
817 	backend->engine.node = dev->of_node;
818 	backend->engine.ops = &sun4i_backend_engine_ops;
819 	backend->engine.id = sun4i_backend_of_get_id(dev->of_node);
820 	if (backend->engine.id < 0)
821 		return backend->engine.id;
822 
823 	backend->frontend = sun4i_backend_find_frontend(drv, dev->of_node);
824 	if (IS_ERR(backend->frontend))
825 		dev_warn(dev, "Couldn't find matching frontend, frontend features disabled\n");
826 
827 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
828 	regs = devm_ioremap_resource(dev, res);
829 	if (IS_ERR(regs))
830 		return PTR_ERR(regs);
831 
832 	backend->reset = devm_reset_control_get(dev, NULL);
833 	if (IS_ERR(backend->reset)) {
834 		dev_err(dev, "Couldn't get our reset line\n");
835 		return PTR_ERR(backend->reset);
836 	}
837 
838 	ret = reset_control_deassert(backend->reset);
839 	if (ret) {
840 		dev_err(dev, "Couldn't deassert our reset line\n");
841 		return ret;
842 	}
843 
844 	backend->bus_clk = devm_clk_get(dev, "ahb");
845 	if (IS_ERR(backend->bus_clk)) {
846 		dev_err(dev, "Couldn't get the backend bus clock\n");
847 		ret = PTR_ERR(backend->bus_clk);
848 		goto err_assert_reset;
849 	}
850 	clk_prepare_enable(backend->bus_clk);
851 
852 	backend->mod_clk = devm_clk_get(dev, "mod");
853 	if (IS_ERR(backend->mod_clk)) {
854 		dev_err(dev, "Couldn't get the backend module clock\n");
855 		ret = PTR_ERR(backend->mod_clk);
856 		goto err_disable_bus_clk;
857 	}
858 
859 	ret = clk_set_rate_exclusive(backend->mod_clk, 300000000);
860 	if (ret) {
861 		dev_err(dev, "Couldn't set the module clock frequency\n");
862 		goto err_disable_bus_clk;
863 	}
864 
865 	clk_prepare_enable(backend->mod_clk);
866 
867 	backend->ram_clk = devm_clk_get(dev, "ram");
868 	if (IS_ERR(backend->ram_clk)) {
869 		dev_err(dev, "Couldn't get the backend RAM clock\n");
870 		ret = PTR_ERR(backend->ram_clk);
871 		goto err_disable_mod_clk;
872 	}
873 	clk_prepare_enable(backend->ram_clk);
874 
875 	if (of_device_is_compatible(dev->of_node,
876 				    "allwinner,sun8i-a33-display-backend")) {
877 		ret = sun4i_backend_init_sat(dev);
878 		if (ret) {
879 			dev_err(dev, "Couldn't init SAT resources\n");
880 			goto err_disable_ram_clk;
881 		}
882 	}
883 
884 	backend->engine.regs = devm_regmap_init_mmio(dev, regs,
885 						     &sun4i_backend_regmap_config);
886 	if (IS_ERR(backend->engine.regs)) {
887 		dev_err(dev, "Couldn't create the backend regmap\n");
888 		return PTR_ERR(backend->engine.regs);
889 	}
890 
891 	list_add_tail(&backend->engine.list, &drv->engine_list);
892 
893 	/*
894 	 * Many of the backend's layer configuration registers have
895 	 * undefined default values. This poses a risk as we use
896 	 * regmap_update_bits in some places, and don't overwrite
897 	 * the whole register.
898 	 *
899 	 * Clear the registers here to have something predictable.
900 	 */
901 	for (i = 0x800; i < 0x1000; i += 4)
902 		regmap_write(backend->engine.regs, i, 0);
903 
904 	/* Disable registers autoloading */
905 	regmap_write(backend->engine.regs, SUN4I_BACKEND_REGBUFFCTL_REG,
906 		     SUN4I_BACKEND_REGBUFFCTL_AUTOLOAD_DIS);
907 
908 	/* Enable the backend */
909 	regmap_write(backend->engine.regs, SUN4I_BACKEND_MODCTL_REG,
910 		     SUN4I_BACKEND_MODCTL_DEBE_EN |
911 		     SUN4I_BACKEND_MODCTL_START_CTL);
912 
913 	/* Set output selection if needed */
914 	quirks = of_device_get_match_data(dev);
915 	if (quirks->needs_output_muxing) {
916 		/*
917 		 * We assume there is no dynamic muxing of backends
918 		 * and TCONs, so we select the backend with same ID.
919 		 *
920 		 * While dynamic selection might be interesting, since
921 		 * the CRTC is tied to the TCON, while the layers are
922 		 * tied to the backends, this means, we will need to
923 		 * switch between groups of layers. There might not be
924 		 * a way to represent this constraint in DRM.
925 		 */
926 		regmap_update_bits(backend->engine.regs,
927 				   SUN4I_BACKEND_MODCTL_REG,
928 				   SUN4I_BACKEND_MODCTL_OUT_SEL,
929 				   (backend->engine.id
930 				    ? SUN4I_BACKEND_MODCTL_OUT_LCD1
931 				    : SUN4I_BACKEND_MODCTL_OUT_LCD0));
932 	}
933 
934 	backend->quirks = quirks;
935 
936 	return 0;
937 
938 err_disable_ram_clk:
939 	clk_disable_unprepare(backend->ram_clk);
940 err_disable_mod_clk:
941 	clk_rate_exclusive_put(backend->mod_clk);
942 	clk_disable_unprepare(backend->mod_clk);
943 err_disable_bus_clk:
944 	clk_disable_unprepare(backend->bus_clk);
945 err_assert_reset:
946 	reset_control_assert(backend->reset);
947 	return ret;
948 }
949 
950 static void sun4i_backend_unbind(struct device *dev, struct device *master,
951 				 void *data)
952 {
953 	struct sun4i_backend *backend = dev_get_drvdata(dev);
954 
955 	list_del(&backend->engine.list);
956 
957 	if (of_device_is_compatible(dev->of_node,
958 				    "allwinner,sun8i-a33-display-backend"))
959 		sun4i_backend_free_sat(dev);
960 
961 	clk_disable_unprepare(backend->ram_clk);
962 	clk_rate_exclusive_put(backend->mod_clk);
963 	clk_disable_unprepare(backend->mod_clk);
964 	clk_disable_unprepare(backend->bus_clk);
965 	reset_control_assert(backend->reset);
966 }
967 
968 static const struct component_ops sun4i_backend_ops = {
969 	.bind	= sun4i_backend_bind,
970 	.unbind	= sun4i_backend_unbind,
971 };
972 
973 static int sun4i_backend_probe(struct platform_device *pdev)
974 {
975 	return component_add(&pdev->dev, &sun4i_backend_ops);
976 }
977 
978 static int sun4i_backend_remove(struct platform_device *pdev)
979 {
980 	component_del(&pdev->dev, &sun4i_backend_ops);
981 
982 	return 0;
983 }
984 
985 static const struct sun4i_backend_quirks sun4i_backend_quirks = {
986 	.needs_output_muxing = true,
987 };
988 
989 static const struct sun4i_backend_quirks sun5i_backend_quirks = {
990 };
991 
992 static const struct sun4i_backend_quirks sun6i_backend_quirks = {
993 };
994 
995 static const struct sun4i_backend_quirks sun7i_backend_quirks = {
996 	.needs_output_muxing = true,
997 };
998 
999 static const struct sun4i_backend_quirks sun8i_a33_backend_quirks = {
1000 	.supports_lowest_plane_alpha = true,
1001 };
1002 
1003 static const struct sun4i_backend_quirks sun9i_backend_quirks = {
1004 };
1005 
1006 static const struct of_device_id sun4i_backend_of_table[] = {
1007 	{
1008 		.compatible = "allwinner,sun4i-a10-display-backend",
1009 		.data = &sun4i_backend_quirks,
1010 	},
1011 	{
1012 		.compatible = "allwinner,sun5i-a13-display-backend",
1013 		.data = &sun5i_backend_quirks,
1014 	},
1015 	{
1016 		.compatible = "allwinner,sun6i-a31-display-backend",
1017 		.data = &sun6i_backend_quirks,
1018 	},
1019 	{
1020 		.compatible = "allwinner,sun7i-a20-display-backend",
1021 		.data = &sun7i_backend_quirks,
1022 	},
1023 	{
1024 		.compatible = "allwinner,sun8i-a23-display-backend",
1025 		.data = &sun8i_a33_backend_quirks,
1026 	},
1027 	{
1028 		.compatible = "allwinner,sun8i-a33-display-backend",
1029 		.data = &sun8i_a33_backend_quirks,
1030 	},
1031 	{
1032 		.compatible = "allwinner,sun9i-a80-display-backend",
1033 		.data = &sun9i_backend_quirks,
1034 	},
1035 	{ }
1036 };
1037 MODULE_DEVICE_TABLE(of, sun4i_backend_of_table);
1038 
1039 static struct platform_driver sun4i_backend_platform_driver = {
1040 	.probe		= sun4i_backend_probe,
1041 	.remove		= sun4i_backend_remove,
1042 	.driver		= {
1043 		.name		= "sun4i-backend",
1044 		.of_match_table	= sun4i_backend_of_table,
1045 	},
1046 };
1047 module_platform_driver(sun4i_backend_platform_driver);
1048 
1049 MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
1050 MODULE_DESCRIPTION("Allwinner A10 Display Backend Driver");
1051 MODULE_LICENSE("GPL");
1052