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