xref: /openbmc/linux/drivers/dma/bcm2835-dma.c (revision 9cfc5c90)
1 /*
2  * BCM2835 DMA engine support
3  *
4  * This driver only supports cyclic DMA transfers
5  * as needed for the I2S module.
6  *
7  * Author:      Florian Meier <florian.meier@koalo.de>
8  *              Copyright 2013
9  *
10  * Based on
11  *	OMAP DMAengine support by Russell King
12  *
13  *	BCM2708 DMA Driver
14  *	Copyright (C) 2010 Broadcom
15  *
16  *	Raspberry Pi PCM I2S ALSA Driver
17  *	Copyright (c) by Phil Poole 2013
18  *
19  *	MARVELL MMP Peripheral DMA Driver
20  *	Copyright 2012 Marvell International Ltd.
21  *
22  * This program is free software; you can redistribute it and/or modify
23  * it under the terms of the GNU General Public License as published by
24  * the Free Software Foundation; either version 2 of the License, or
25  * (at your option) any later version.
26  *
27  * This program is distributed in the hope that it will be useful,
28  * but WITHOUT ANY WARRANTY; without even the implied warranty of
29  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
30  * GNU General Public License for more details.
31  */
32 #include <linux/dmaengine.h>
33 #include <linux/dma-mapping.h>
34 #include <linux/err.h>
35 #include <linux/init.h>
36 #include <linux/interrupt.h>
37 #include <linux/list.h>
38 #include <linux/module.h>
39 #include <linux/platform_device.h>
40 #include <linux/slab.h>
41 #include <linux/io.h>
42 #include <linux/spinlock.h>
43 #include <linux/of.h>
44 #include <linux/of_dma.h>
45 
46 #include "virt-dma.h"
47 
48 struct bcm2835_dmadev {
49 	struct dma_device ddev;
50 	spinlock_t lock;
51 	void __iomem *base;
52 	struct device_dma_parameters dma_parms;
53 };
54 
55 struct bcm2835_dma_cb {
56 	uint32_t info;
57 	uint32_t src;
58 	uint32_t dst;
59 	uint32_t length;
60 	uint32_t stride;
61 	uint32_t next;
62 	uint32_t pad[2];
63 };
64 
65 struct bcm2835_chan {
66 	struct virt_dma_chan vc;
67 	struct list_head node;
68 
69 	struct dma_slave_config	cfg;
70 	bool cyclic;
71 	unsigned int dreq;
72 
73 	int ch;
74 	struct bcm2835_desc *desc;
75 
76 	void __iomem *chan_base;
77 	int irq_number;
78 };
79 
80 struct bcm2835_desc {
81 	struct virt_dma_desc vd;
82 	enum dma_transfer_direction dir;
83 
84 	unsigned int control_block_size;
85 	struct bcm2835_dma_cb *control_block_base;
86 	dma_addr_t control_block_base_phys;
87 
88 	unsigned int frames;
89 	size_t size;
90 };
91 
92 #define BCM2835_DMA_CS		0x00
93 #define BCM2835_DMA_ADDR	0x04
94 #define BCM2835_DMA_SOURCE_AD	0x0c
95 #define BCM2835_DMA_DEST_AD	0x10
96 #define BCM2835_DMA_NEXTCB	0x1C
97 
98 /* DMA CS Control and Status bits */
99 #define BCM2835_DMA_ACTIVE	BIT(0)
100 #define BCM2835_DMA_INT	BIT(2)
101 #define BCM2835_DMA_ISPAUSED	BIT(4)  /* Pause requested or not active */
102 #define BCM2835_DMA_ISHELD	BIT(5)  /* Is held by DREQ flow control */
103 #define BCM2835_DMA_ERR	BIT(8)
104 #define BCM2835_DMA_ABORT	BIT(30) /* Stop current CB, go to next, WO */
105 #define BCM2835_DMA_RESET	BIT(31) /* WO, self clearing */
106 
107 #define BCM2835_DMA_INT_EN	BIT(0)
108 #define BCM2835_DMA_D_INC	BIT(4)
109 #define BCM2835_DMA_D_DREQ	BIT(6)
110 #define BCM2835_DMA_S_INC	BIT(8)
111 #define BCM2835_DMA_S_DREQ	BIT(10)
112 
113 #define BCM2835_DMA_PER_MAP(x)	((x) << 16)
114 
115 #define BCM2835_DMA_DATA_TYPE_S8	1
116 #define BCM2835_DMA_DATA_TYPE_S16	2
117 #define BCM2835_DMA_DATA_TYPE_S32	4
118 #define BCM2835_DMA_DATA_TYPE_S128	16
119 
120 #define BCM2835_DMA_BULK_MASK	BIT(0)
121 #define BCM2835_DMA_FIQ_MASK	(BIT(2) | BIT(3))
122 
123 /* Valid only for channels 0 - 14, 15 has its own base address */
124 #define BCM2835_DMA_CHAN(n)	((n) << 8) /* Base address */
125 #define BCM2835_DMA_CHANIO(base, n) ((base) + BCM2835_DMA_CHAN(n))
126 
127 static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
128 {
129 	return container_of(d, struct bcm2835_dmadev, ddev);
130 }
131 
132 static inline struct bcm2835_chan *to_bcm2835_dma_chan(struct dma_chan *c)
133 {
134 	return container_of(c, struct bcm2835_chan, vc.chan);
135 }
136 
137 static inline struct bcm2835_desc *to_bcm2835_dma_desc(
138 		struct dma_async_tx_descriptor *t)
139 {
140 	return container_of(t, struct bcm2835_desc, vd.tx);
141 }
142 
143 static void bcm2835_dma_desc_free(struct virt_dma_desc *vd)
144 {
145 	struct bcm2835_desc *desc = container_of(vd, struct bcm2835_desc, vd);
146 	dma_free_coherent(desc->vd.tx.chan->device->dev,
147 			desc->control_block_size,
148 			desc->control_block_base,
149 			desc->control_block_base_phys);
150 	kfree(desc);
151 }
152 
153 static int bcm2835_dma_abort(void __iomem *chan_base)
154 {
155 	unsigned long cs;
156 	long int timeout = 10000;
157 
158 	cs = readl(chan_base + BCM2835_DMA_CS);
159 	if (!(cs & BCM2835_DMA_ACTIVE))
160 		return 0;
161 
162 	/* Write 0 to the active bit - Pause the DMA */
163 	writel(0, chan_base + BCM2835_DMA_CS);
164 
165 	/* Wait for any current AXI transfer to complete */
166 	while ((cs & BCM2835_DMA_ISPAUSED) && --timeout) {
167 		cpu_relax();
168 		cs = readl(chan_base + BCM2835_DMA_CS);
169 	}
170 
171 	/* We'll un-pause when we set of our next DMA */
172 	if (!timeout)
173 		return -ETIMEDOUT;
174 
175 	if (!(cs & BCM2835_DMA_ACTIVE))
176 		return 0;
177 
178 	/* Terminate the control block chain */
179 	writel(0, chan_base + BCM2835_DMA_NEXTCB);
180 
181 	/* Abort the whole DMA */
182 	writel(BCM2835_DMA_ABORT | BCM2835_DMA_ACTIVE,
183 	       chan_base + BCM2835_DMA_CS);
184 
185 	return 0;
186 }
187 
188 static void bcm2835_dma_start_desc(struct bcm2835_chan *c)
189 {
190 	struct virt_dma_desc *vd = vchan_next_desc(&c->vc);
191 	struct bcm2835_desc *d;
192 
193 	if (!vd) {
194 		c->desc = NULL;
195 		return;
196 	}
197 
198 	list_del(&vd->node);
199 
200 	c->desc = d = to_bcm2835_dma_desc(&vd->tx);
201 
202 	writel(d->control_block_base_phys, c->chan_base + BCM2835_DMA_ADDR);
203 	writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
204 }
205 
206 static irqreturn_t bcm2835_dma_callback(int irq, void *data)
207 {
208 	struct bcm2835_chan *c = data;
209 	struct bcm2835_desc *d;
210 	unsigned long flags;
211 
212 	spin_lock_irqsave(&c->vc.lock, flags);
213 
214 	/* Acknowledge interrupt */
215 	writel(BCM2835_DMA_INT, c->chan_base + BCM2835_DMA_CS);
216 
217 	d = c->desc;
218 
219 	if (d) {
220 		/* TODO Only works for cyclic DMA */
221 		vchan_cyclic_callback(&d->vd);
222 	}
223 
224 	/* Keep the DMA engine running */
225 	writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
226 
227 	spin_unlock_irqrestore(&c->vc.lock, flags);
228 
229 	return IRQ_HANDLED;
230 }
231 
232 static int bcm2835_dma_alloc_chan_resources(struct dma_chan *chan)
233 {
234 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
235 
236 	dev_dbg(c->vc.chan.device->dev,
237 			"Allocating DMA channel %d\n", c->ch);
238 
239 	return request_irq(c->irq_number,
240 			bcm2835_dma_callback, 0, "DMA IRQ", c);
241 }
242 
243 static void bcm2835_dma_free_chan_resources(struct dma_chan *chan)
244 {
245 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
246 
247 	vchan_free_chan_resources(&c->vc);
248 	free_irq(c->irq_number, c);
249 
250 	dev_dbg(c->vc.chan.device->dev, "Freeing DMA channel %u\n", c->ch);
251 }
252 
253 static size_t bcm2835_dma_desc_size(struct bcm2835_desc *d)
254 {
255 	return d->size;
256 }
257 
258 static size_t bcm2835_dma_desc_size_pos(struct bcm2835_desc *d, dma_addr_t addr)
259 {
260 	unsigned int i;
261 	size_t size;
262 
263 	for (size = i = 0; i < d->frames; i++) {
264 		struct bcm2835_dma_cb *control_block =
265 			&d->control_block_base[i];
266 		size_t this_size = control_block->length;
267 		dma_addr_t dma;
268 
269 		if (d->dir == DMA_DEV_TO_MEM)
270 			dma = control_block->dst;
271 		else
272 			dma = control_block->src;
273 
274 		if (size)
275 			size += this_size;
276 		else if (addr >= dma && addr < dma + this_size)
277 			size += dma + this_size - addr;
278 	}
279 
280 	return size;
281 }
282 
283 static enum dma_status bcm2835_dma_tx_status(struct dma_chan *chan,
284 	dma_cookie_t cookie, struct dma_tx_state *txstate)
285 {
286 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
287 	struct virt_dma_desc *vd;
288 	enum dma_status ret;
289 	unsigned long flags;
290 
291 	ret = dma_cookie_status(chan, cookie, txstate);
292 	if (ret == DMA_COMPLETE || !txstate)
293 		return ret;
294 
295 	spin_lock_irqsave(&c->vc.lock, flags);
296 	vd = vchan_find_desc(&c->vc, cookie);
297 	if (vd) {
298 		txstate->residue =
299 			bcm2835_dma_desc_size(to_bcm2835_dma_desc(&vd->tx));
300 	} else if (c->desc && c->desc->vd.tx.cookie == cookie) {
301 		struct bcm2835_desc *d = c->desc;
302 		dma_addr_t pos;
303 
304 		if (d->dir == DMA_MEM_TO_DEV)
305 			pos = readl(c->chan_base + BCM2835_DMA_SOURCE_AD);
306 		else if (d->dir == DMA_DEV_TO_MEM)
307 			pos = readl(c->chan_base + BCM2835_DMA_DEST_AD);
308 		else
309 			pos = 0;
310 
311 		txstate->residue = bcm2835_dma_desc_size_pos(d, pos);
312 	} else {
313 		txstate->residue = 0;
314 	}
315 
316 	spin_unlock_irqrestore(&c->vc.lock, flags);
317 
318 	return ret;
319 }
320 
321 static void bcm2835_dma_issue_pending(struct dma_chan *chan)
322 {
323 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
324 	unsigned long flags;
325 
326 	c->cyclic = true; /* Nothing else is implemented */
327 
328 	spin_lock_irqsave(&c->vc.lock, flags);
329 	if (vchan_issue_pending(&c->vc) && !c->desc)
330 		bcm2835_dma_start_desc(c);
331 
332 	spin_unlock_irqrestore(&c->vc.lock, flags);
333 }
334 
335 static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
336 	struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
337 	size_t period_len, enum dma_transfer_direction direction,
338 	unsigned long flags)
339 {
340 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
341 	enum dma_slave_buswidth dev_width;
342 	struct bcm2835_desc *d;
343 	dma_addr_t dev_addr;
344 	unsigned int es, sync_type;
345 	unsigned int frame;
346 
347 	/* Grab configuration */
348 	if (!is_slave_direction(direction)) {
349 		dev_err(chan->device->dev, "%s: bad direction?\n", __func__);
350 		return NULL;
351 	}
352 
353 	if (direction == DMA_DEV_TO_MEM) {
354 		dev_addr = c->cfg.src_addr;
355 		dev_width = c->cfg.src_addr_width;
356 		sync_type = BCM2835_DMA_S_DREQ;
357 	} else {
358 		dev_addr = c->cfg.dst_addr;
359 		dev_width = c->cfg.dst_addr_width;
360 		sync_type = BCM2835_DMA_D_DREQ;
361 	}
362 
363 	/* Bus width translates to the element size (ES) */
364 	switch (dev_width) {
365 	case DMA_SLAVE_BUSWIDTH_4_BYTES:
366 		es = BCM2835_DMA_DATA_TYPE_S32;
367 		break;
368 	default:
369 		return NULL;
370 	}
371 
372 	/* Now allocate and setup the descriptor. */
373 	d = kzalloc(sizeof(*d), GFP_NOWAIT);
374 	if (!d)
375 		return NULL;
376 
377 	d->dir = direction;
378 	d->frames = buf_len / period_len;
379 
380 	/* Allocate memory for control blocks */
381 	d->control_block_size = d->frames * sizeof(struct bcm2835_dma_cb);
382 	d->control_block_base = dma_zalloc_coherent(chan->device->dev,
383 			d->control_block_size, &d->control_block_base_phys,
384 			GFP_NOWAIT);
385 
386 	if (!d->control_block_base) {
387 		kfree(d);
388 		return NULL;
389 	}
390 
391 	/*
392 	 * Iterate over all frames, create a control block
393 	 * for each frame and link them together.
394 	 */
395 	for (frame = 0; frame < d->frames; frame++) {
396 		struct bcm2835_dma_cb *control_block =
397 			&d->control_block_base[frame];
398 
399 		/* Setup adresses */
400 		if (d->dir == DMA_DEV_TO_MEM) {
401 			control_block->info = BCM2835_DMA_D_INC;
402 			control_block->src = dev_addr;
403 			control_block->dst = buf_addr + frame * period_len;
404 		} else {
405 			control_block->info = BCM2835_DMA_S_INC;
406 			control_block->src = buf_addr + frame * period_len;
407 			control_block->dst = dev_addr;
408 		}
409 
410 		/* Enable interrupt */
411 		control_block->info |= BCM2835_DMA_INT_EN;
412 
413 		/* Setup synchronization */
414 		if (sync_type != 0)
415 			control_block->info |= sync_type;
416 
417 		/* Setup DREQ channel */
418 		if (c->dreq != 0)
419 			control_block->info |=
420 				BCM2835_DMA_PER_MAP(c->dreq);
421 
422 		/* Length of a frame */
423 		control_block->length = period_len;
424 		d->size += control_block->length;
425 
426 		/*
427 		 * Next block is the next frame.
428 		 * This DMA engine driver currently only supports cyclic DMA.
429 		 * Therefore, wrap around at number of frames.
430 		 */
431 		control_block->next = d->control_block_base_phys +
432 			sizeof(struct bcm2835_dma_cb)
433 			* ((frame + 1) % d->frames);
434 	}
435 
436 	return vchan_tx_prep(&c->vc, &d->vd, flags);
437 }
438 
439 static int bcm2835_dma_slave_config(struct dma_chan *chan,
440 				    struct dma_slave_config *cfg)
441 {
442 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
443 
444 	if ((cfg->direction == DMA_DEV_TO_MEM &&
445 	     cfg->src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES) ||
446 	    (cfg->direction == DMA_MEM_TO_DEV &&
447 	     cfg->dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES) ||
448 	    !is_slave_direction(cfg->direction)) {
449 		return -EINVAL;
450 	}
451 
452 	c->cfg = *cfg;
453 
454 	return 0;
455 }
456 
457 static int bcm2835_dma_terminate_all(struct dma_chan *chan)
458 {
459 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
460 	struct bcm2835_dmadev *d = to_bcm2835_dma_dev(c->vc.chan.device);
461 	unsigned long flags;
462 	int timeout = 10000;
463 	LIST_HEAD(head);
464 
465 	spin_lock_irqsave(&c->vc.lock, flags);
466 
467 	/* Prevent this channel being scheduled */
468 	spin_lock(&d->lock);
469 	list_del_init(&c->node);
470 	spin_unlock(&d->lock);
471 
472 	/*
473 	 * Stop DMA activity: we assume the callback will not be called
474 	 * after bcm_dma_abort() returns (even if it does, it will see
475 	 * c->desc is NULL and exit.)
476 	 */
477 	if (c->desc) {
478 		bcm2835_dma_desc_free(&c->desc->vd);
479 		c->desc = NULL;
480 		bcm2835_dma_abort(c->chan_base);
481 
482 		/* Wait for stopping */
483 		while (--timeout) {
484 			if (!(readl(c->chan_base + BCM2835_DMA_CS) &
485 						BCM2835_DMA_ACTIVE))
486 				break;
487 
488 			cpu_relax();
489 		}
490 
491 		if (!timeout)
492 			dev_err(d->ddev.dev, "DMA transfer could not be terminated\n");
493 	}
494 
495 	vchan_get_all_descriptors(&c->vc, &head);
496 	spin_unlock_irqrestore(&c->vc.lock, flags);
497 	vchan_dma_desc_free_list(&c->vc, &head);
498 
499 	return 0;
500 }
501 
502 static int bcm2835_dma_chan_init(struct bcm2835_dmadev *d, int chan_id, int irq)
503 {
504 	struct bcm2835_chan *c;
505 
506 	c = devm_kzalloc(d->ddev.dev, sizeof(*c), GFP_KERNEL);
507 	if (!c)
508 		return -ENOMEM;
509 
510 	c->vc.desc_free = bcm2835_dma_desc_free;
511 	vchan_init(&c->vc, &d->ddev);
512 	INIT_LIST_HEAD(&c->node);
513 
514 	c->chan_base = BCM2835_DMA_CHANIO(d->base, chan_id);
515 	c->ch = chan_id;
516 	c->irq_number = irq;
517 
518 	return 0;
519 }
520 
521 static void bcm2835_dma_free(struct bcm2835_dmadev *od)
522 {
523 	struct bcm2835_chan *c, *next;
524 
525 	list_for_each_entry_safe(c, next, &od->ddev.channels,
526 				 vc.chan.device_node) {
527 		list_del(&c->vc.chan.device_node);
528 		tasklet_kill(&c->vc.task);
529 	}
530 }
531 
532 static const struct of_device_id bcm2835_dma_of_match[] = {
533 	{ .compatible = "brcm,bcm2835-dma", },
534 	{},
535 };
536 MODULE_DEVICE_TABLE(of, bcm2835_dma_of_match);
537 
538 static struct dma_chan *bcm2835_dma_xlate(struct of_phandle_args *spec,
539 					   struct of_dma *ofdma)
540 {
541 	struct bcm2835_dmadev *d = ofdma->of_dma_data;
542 	struct dma_chan *chan;
543 
544 	chan = dma_get_any_slave_channel(&d->ddev);
545 	if (!chan)
546 		return NULL;
547 
548 	/* Set DREQ from param */
549 	to_bcm2835_dma_chan(chan)->dreq = spec->args[0];
550 
551 	return chan;
552 }
553 
554 static int bcm2835_dma_probe(struct platform_device *pdev)
555 {
556 	struct bcm2835_dmadev *od;
557 	struct resource *res;
558 	void __iomem *base;
559 	int rc;
560 	int i;
561 	int irq;
562 	uint32_t chans_available;
563 
564 	if (!pdev->dev.dma_mask)
565 		pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
566 
567 	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
568 	if (rc)
569 		return rc;
570 
571 	od = devm_kzalloc(&pdev->dev, sizeof(*od), GFP_KERNEL);
572 	if (!od)
573 		return -ENOMEM;
574 
575 	pdev->dev.dma_parms = &od->dma_parms;
576 	dma_set_max_seg_size(&pdev->dev, 0x3FFFFFFF);
577 
578 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
579 	base = devm_ioremap_resource(&pdev->dev, res);
580 	if (IS_ERR(base))
581 		return PTR_ERR(base);
582 
583 	od->base = base;
584 
585 	dma_cap_set(DMA_SLAVE, od->ddev.cap_mask);
586 	dma_cap_set(DMA_PRIVATE, od->ddev.cap_mask);
587 	dma_cap_set(DMA_CYCLIC, od->ddev.cap_mask);
588 	od->ddev.device_alloc_chan_resources = bcm2835_dma_alloc_chan_resources;
589 	od->ddev.device_free_chan_resources = bcm2835_dma_free_chan_resources;
590 	od->ddev.device_tx_status = bcm2835_dma_tx_status;
591 	od->ddev.device_issue_pending = bcm2835_dma_issue_pending;
592 	od->ddev.device_prep_dma_cyclic = bcm2835_dma_prep_dma_cyclic;
593 	od->ddev.device_config = bcm2835_dma_slave_config;
594 	od->ddev.device_terminate_all = bcm2835_dma_terminate_all;
595 	od->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
596 	od->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
597 	od->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
598 	od->ddev.dev = &pdev->dev;
599 	INIT_LIST_HEAD(&od->ddev.channels);
600 	spin_lock_init(&od->lock);
601 
602 	platform_set_drvdata(pdev, od);
603 
604 	/* Request DMA channel mask from device tree */
605 	if (of_property_read_u32(pdev->dev.of_node,
606 			"brcm,dma-channel-mask",
607 			&chans_available)) {
608 		dev_err(&pdev->dev, "Failed to get channel mask\n");
609 		rc = -EINVAL;
610 		goto err_no_dma;
611 	}
612 
613 	/*
614 	 * Do not use the FIQ and BULK channels,
615 	 * because they are used by the GPU.
616 	 */
617 	chans_available &= ~(BCM2835_DMA_FIQ_MASK | BCM2835_DMA_BULK_MASK);
618 
619 	for (i = 0; i < pdev->num_resources; i++) {
620 		irq = platform_get_irq(pdev, i);
621 		if (irq < 0)
622 			break;
623 
624 		if (chans_available & (1 << i)) {
625 			rc = bcm2835_dma_chan_init(od, i, irq);
626 			if (rc)
627 				goto err_no_dma;
628 		}
629 	}
630 
631 	dev_dbg(&pdev->dev, "Initialized %i DMA channels\n", i);
632 
633 	/* Device-tree DMA controller registration */
634 	rc = of_dma_controller_register(pdev->dev.of_node,
635 			bcm2835_dma_xlate, od);
636 	if (rc) {
637 		dev_err(&pdev->dev, "Failed to register DMA controller\n");
638 		goto err_no_dma;
639 	}
640 
641 	rc = dma_async_device_register(&od->ddev);
642 	if (rc) {
643 		dev_err(&pdev->dev,
644 			"Failed to register slave DMA engine device: %d\n", rc);
645 		goto err_no_dma;
646 	}
647 
648 	dev_dbg(&pdev->dev, "Load BCM2835 DMA engine driver\n");
649 
650 	return 0;
651 
652 err_no_dma:
653 	bcm2835_dma_free(od);
654 	return rc;
655 }
656 
657 static int bcm2835_dma_remove(struct platform_device *pdev)
658 {
659 	struct bcm2835_dmadev *od = platform_get_drvdata(pdev);
660 
661 	dma_async_device_unregister(&od->ddev);
662 	bcm2835_dma_free(od);
663 
664 	return 0;
665 }
666 
667 static struct platform_driver bcm2835_dma_driver = {
668 	.probe	= bcm2835_dma_probe,
669 	.remove	= bcm2835_dma_remove,
670 	.driver = {
671 		.name = "bcm2835-dma",
672 		.of_match_table = of_match_ptr(bcm2835_dma_of_match),
673 	},
674 };
675 
676 module_platform_driver(bcm2835_dma_driver);
677 
678 MODULE_ALIAS("platform:bcm2835-dma");
679 MODULE_DESCRIPTION("BCM2835 DMA engine driver");
680 MODULE_AUTHOR("Florian Meier <florian.meier@koalo.de>");
681 MODULE_LICENSE("GPL v2");
682