target/linux/ramips/patches-3.10/0300-DMA-add-rt2880-dma-engine.patch

   1 From 776726ff626249276936a7e1f865103ea4e1b7e9 Mon Sep 17 00:00:00 2001
   2 From: John Crispin <blogic@openwrt.org>
   3 Date: Tue, 3 Dec 2013 17:05:05 +0100
   4 Subject: [PATCH] DMA: add rt2880 dma engine
   5
   6 Signed-off-by: John Crispin <blogic@openwrt.org>
   7 ---
   8  drivers/dma/Kconfig       |    6 +
   9  drivers/dma/Makefile      |    1 +
  10  drivers/dma/ralink-gdma.c |  596 +++++++++++++++++++++++++++++++++++++++++++++
  11  3 files changed, 603 insertions(+)
  12  create mode 100644 drivers/dma/ralink-gdma.c
  13
  14 --- a/drivers/dma/Kconfig
  15 +++ b/drivers/dma/Kconfig
  16 @@ -312,6 +312,12 @@ config MMP_PDMA
  17         help
  18           Support the MMP PDMA engine for PXA and MMP platfrom.
  19
  20 +config DMA_RALINK
  21 +       tristate "RALINK DMA support"
  22 +       depends on RALINK && SOC_MT7620
  23 +       select DMA_ENGINE
  24 +       select DMA_VIRTUAL_CHANNELS
  25 +
  26  config DMA_ENGINE
  27         bool
  28
  29 --- /dev/null
  30 +++ b/drivers/dma/ralink-gdma.c
  31 @@ -0,0 +1,577 @@
  32 +/*
  33 + *  Copyright (C) 2013, Lars-Peter Clausen <lars@metafoo.de>
  34 + *  GDMA4740 DMAC support
  35 + *
  36 + *  This program is free software; you can redistribute it and/or modify it
  37 + *  under  the terms of the GNU General         Public License as published by the
  38 + *  Free Software Foundation;  either version 2 of the License, or (at your
  39 + *  option) any later version.
  40 + *
  41 + *  You should have received a copy of the GNU General Public License along
  42 + *  with this program; if not, write to the Free Software Foundation, Inc.,
  43 + *  675 Mass Ave, Cambridge, MA 02139, USA.
  44 + *
  45 + */
  46 +
  47 +#include <linux/dmaengine.h>
  48 +#include <linux/dma-mapping.h>
  49 +#include <linux/err.h>
  50 +#include <linux/init.h>
  51 +#include <linux/list.h>
  52 +#include <linux/module.h>
  53 +#include <linux/platform_device.h>
  54 +#include <linux/slab.h>
  55 +#include <linux/spinlock.h>
  56 +#include <linux/irq.h>
  57 +#include <linux/of_dma.h>
  58 +
  59 +#include "virt-dma.h"
  60 +
  61 +#define GDMA_NR_CHANS                  16
  62 +
  63 +#define GDMA_REG_SRC_ADDR(x)           (0x00 + (x) * 0x10)
  64 +#define GDMA_REG_DST_ADDR(x)           (0x04 + (x) * 0x10)
  65 +
  66 +#define GDMA_REG_CTRL0(x)              (0x08 + (x) * 0x10)
  67 +#define GDMA_REG_CTRL0_TX_MASK         0xffff
  68 +#define GDMA_REG_CTRL0_TX_SHIFT                16
  69 +#define GDMA_REG_CTRL0_CURR_MASK       0xff
  70 +#define GDMA_REG_CTRL0_CURR_SHIFT      8
  71 +#define        GDMA_REG_CTRL0_SRC_ADDR_FIXED   BIT(7)
  72 +#define GDMA_REG_CTRL0_DST_ADDR_FIXED  BIT(6)
  73 +#define GDMA_REG_CTRL0_BURST_MASK      0x7
  74 +#define GDMA_REG_CTRL0_BURST_SHIFT     3
  75 +#define        GDMA_REG_CTRL0_DONE_INT         BIT(2)
  76 +#define        GDMA_REG_CTRL0_ENABLE           BIT(1)
  77 +#define        GDMA_REG_CTRL0_HW_MODE          0
  78 +
  79 +#define GDMA_REG_CTRL1(x)              (0x0c + (x) * 0x10)
  80 +#define GDMA_REG_CTRL1_SEG_MASK                0xf
  81 +#define GDMA_REG_CTRL1_SEG_SHIFT       22
  82 +#define GDMA_REG_CTRL1_REQ_MASK                0x3f
  83 +#define GDMA_REG_CTRL1_SRC_REQ_SHIFT   16
  84 +#define GDMA_REG_CTRL1_DST_REQ_SHIFT   8
  85 +#define GDMA_REG_CTRL1_CONTINOUS       BIT(14)
  86 +#define GDMA_REG_CTRL1_NEXT_MASK       0x1f
  87 +#define GDMA_REG_CTRL1_NEXT_SHIFT      3
  88 +#define GDMA_REG_CTRL1_COHERENT                BIT(2)
  89 +#define GDMA_REG_CTRL1_FAIL            BIT(1)
  90 +#define GDMA_REG_CTRL1_MASK            BIT(0)
  91 +
  92 +#define GDMA_REG_UNMASK_INT            0x200
  93 +#define GDMA_REG_DONE_INT              0x204
  94 +
  95 +#define GDMA_REG_GCT                   0x220
  96 +#define GDMA_REG_GCT_CHAN_MASK         0x3
  97 +#define GDMA_REG_GCT_CHAN_SHIFT                3
  98 +#define GDMA_REG_GCT_VER_MASK          0x3
  99 +#define GDMA_REG_GCT_VER_SHIFT         1
 100 +#define GDMA_REG_GCT_ARBIT_RR          BIT(0)
 101 +
 102 +enum gdma_dma_transfer_size {
 103 +       GDMA_TRANSFER_SIZE_4BYTE        = 0,
 104 +       GDMA_TRANSFER_SIZE_8BYTE        = 1,
 105 +       GDMA_TRANSFER_SIZE_16BYTE       = 2,
 106 +       GDMA_TRANSFER_SIZE_32BYTE       = 3,
 107 +};
 108 +
 109 +struct gdma_dma_sg {
 110 +       dma_addr_t addr;
 111 +       unsigned int len;
 112 +};
 113 +
 114 +struct gdma_dma_desc {
 115 +       struct virt_dma_desc vdesc;
 116 +
 117 +       enum dma_transfer_direction direction;
 118 +       bool cyclic;
 119 +
 120 +       unsigned int num_sgs;
 121 +       struct gdma_dma_sg sg[];
 122 +};
 123 +
 124 +struct gdma_dmaengine_chan {
 125 +       struct virt_dma_chan vchan;
 126 +       unsigned int id;
 127 +
 128 +       dma_addr_t fifo_addr;
 129 +       unsigned int transfer_shift;
 130 +
 131 +       struct gdma_dma_desc *desc;
 132 +       unsigned int next_sg;
 133 +};
 134 +
 135 +struct gdma_dma_dev {
 136 +       struct dma_device ddev;
 137 +       void __iomem *base;
 138 +       struct clk *clk;
 139 +
 140 +       struct gdma_dmaengine_chan chan[GDMA_NR_CHANS];
 141 +};
 142 +
 143 +static struct gdma_dma_dev *gdma_dma_chan_get_dev(
 144 +       struct gdma_dmaengine_chan *chan)
 145 +{
 146 +       return container_of(chan->vchan.chan.device, struct gdma_dma_dev,
 147 +               ddev);
 148 +}
 149 +
 150 +static struct gdma_dmaengine_chan *to_gdma_dma_chan(struct dma_chan *c)
 151 +{
 152 +       return container_of(c, struct gdma_dmaengine_chan, vchan.chan);
 153 +}
 154 +
 155 +static struct gdma_dma_desc *to_gdma_dma_desc(struct virt_dma_desc *vdesc)
 156 +{
 157 +       return container_of(vdesc, struct gdma_dma_desc, vdesc);
 158 +}
 159 +
 160 +static inline uint32_t gdma_dma_read(struct gdma_dma_dev *dma_dev,
 161 +       unsigned int reg)
 162 +{
 163 +       return readl(dma_dev->base + reg);
 164 +}
 165 +
 166 +static inline void gdma_dma_write(struct gdma_dma_dev *dma_dev,
 167 +       unsigned reg, uint32_t val)
 168 +{
 169 +       //printk("gdma --> %p = 0x%08X\n", dma_dev->base + reg, val);
 170 +       writel(val, dma_dev->base + reg);
 171 +}
 172 +
 173 +static inline void gdma_dma_write_mask(struct gdma_dma_dev *dma_dev,
 174 +       unsigned int reg, uint32_t val, uint32_t mask)
 175 +{
 176 +       uint32_t tmp;
 177 +
 178 +       tmp = gdma_dma_read(dma_dev, reg);
 179 +       tmp &= ~mask;
 180 +       tmp |= val;
 181 +       gdma_dma_write(dma_dev, reg, tmp);
 182 +}
 183 +
 184 +static struct gdma_dma_desc *gdma_dma_alloc_desc(unsigned int num_sgs)
 185 +{
 186 +       return kzalloc(sizeof(struct gdma_dma_desc) +
 187 +               sizeof(struct gdma_dma_sg) * num_sgs, GFP_ATOMIC);
 188 +}
 189 +
 190 +static enum gdma_dma_transfer_size gdma_dma_maxburst(u32 maxburst)
 191 +{
 192 +       if (maxburst <= 7)
 193 +               return GDMA_TRANSFER_SIZE_4BYTE;
 194 +       else if (maxburst <= 15)
 195 +               return GDMA_TRANSFER_SIZE_8BYTE;
 196 +       else if (maxburst <= 31)
 197 +               return GDMA_TRANSFER_SIZE_16BYTE;
 198 +
 199 +       return GDMA_TRANSFER_SIZE_32BYTE;
 200 +}
 201 +
 202 +static int gdma_dma_slave_config(struct dma_chan *c,
 203 +       const struct dma_slave_config *config)
 204 +{
 205 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 206 +       struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
 207 +       enum gdma_dma_transfer_size transfer_size;
 208 +       uint32_t flags;
 209 +       uint32_t ctrl0, ctrl1;
 210 +
 211 +       switch (config->direction) {
 212 +       case DMA_MEM_TO_DEV:
 213 +               ctrl1 = 32 << GDMA_REG_CTRL1_SRC_REQ_SHIFT;
 214 +               ctrl1 |= config->slave_id << GDMA_REG_CTRL1_DST_REQ_SHIFT;
 215 +               flags = GDMA_REG_CTRL0_DST_ADDR_FIXED;
 216 +               transfer_size = gdma_dma_maxburst(config->dst_maxburst);
 217 +               chan->fifo_addr = config->dst_addr;
 218 +               break;
 219 +
 220 +       case DMA_DEV_TO_MEM:
 221 +               ctrl1 = config->slave_id << GDMA_REG_CTRL1_SRC_REQ_SHIFT;
 222 +               ctrl1 |= 32 << GDMA_REG_CTRL1_DST_REQ_SHIFT;
 223 +               flags = GDMA_REG_CTRL0_SRC_ADDR_FIXED;
 224 +               transfer_size = gdma_dma_maxburst(config->src_maxburst);
 225 +               chan->fifo_addr = config->src_addr;
 226 +               break;
 227 +
 228 +       default:
 229 +               return -EINVAL;
 230 +       }
 231 +
 232 +       chan->transfer_shift = 1 + transfer_size;
 233 +
 234 +       ctrl0 = flags | GDMA_REG_CTRL0_HW_MODE;
 235 +       ctrl0 |= GDMA_REG_CTRL0_DONE_INT;
 236 +
 237 +       ctrl1 &= ~(GDMA_REG_CTRL1_NEXT_MASK << GDMA_REG_CTRL1_NEXT_SHIFT);
 238 +       ctrl1 |= chan->id << GDMA_REG_CTRL1_NEXT_SHIFT;
 239 +       ctrl1 |= GDMA_REG_CTRL1_FAIL;
 240 +       ctrl1 &= ~GDMA_REG_CTRL1_CONTINOUS;
 241 +       gdma_dma_write(dma_dev, GDMA_REG_CTRL0(chan->id), ctrl0);
 242 +       gdma_dma_write(dma_dev, GDMA_REG_CTRL1(chan->id), ctrl1);
 243 +
 244 +       return 0;
 245 +}
 246 +
 247 +static int gdma_dma_terminate_all(struct dma_chan *c)
 248 +{
 249 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 250 +       struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
 251 +       unsigned long flags;
 252 +       LIST_HEAD(head);
 253 +
 254 +       spin_lock_irqsave(&chan->vchan.lock, flags);
 255 +       gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id), 0,
 256 +                       GDMA_REG_CTRL0_ENABLE);
 257 +       chan->desc = NULL;
 258 +       vchan_get_all_descriptors(&chan->vchan, &head);
 259 +       spin_unlock_irqrestore(&chan->vchan.lock, flags);
 260 +
 261 +       vchan_dma_desc_free_list(&chan->vchan, &head);
 262 +
 263 +       return 0;
 264 +}
 265 +
 266 +static int gdma_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 267 +       unsigned long arg)
 268 +{
 269 +       struct dma_slave_config *config = (struct dma_slave_config *)arg;
 270 +
 271 +       switch (cmd) {
 272 +       case DMA_SLAVE_CONFIG:
 273 +               return gdma_dma_slave_config(chan, config);
 274 +       case DMA_TERMINATE_ALL:
 275 +               return gdma_dma_terminate_all(chan);
 276 +       default:
 277 +               return -ENOSYS;
 278 +       }
 279 +}
 280 +
 281 +static int gdma_dma_start_transfer(struct gdma_dmaengine_chan *chan)
 282 +{
 283 +       struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
 284 +       dma_addr_t src_addr, dst_addr;
 285 +       struct virt_dma_desc *vdesc;
 286 +       struct gdma_dma_sg *sg;
 287 +
 288 +       gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id), 0,
 289 +                       GDMA_REG_CTRL0_ENABLE);
 290 +
 291 +       if (!chan->desc) {
 292 +               vdesc = vchan_next_desc(&chan->vchan);
 293 +               if (!vdesc)
 294 +                       return 0;
 295 +               chan->desc = to_gdma_dma_desc(vdesc);
 296 +               chan->next_sg = 0;
 297 +       }
 298 +
 299 +       if (chan->next_sg == chan->desc->num_sgs)
 300 +               chan->next_sg = 0;
 301 +
 302 +       sg = &chan->desc->sg[chan->next_sg];
 303 +
 304 +       if (chan->desc->direction == DMA_MEM_TO_DEV) {
 305 +               src_addr = sg->addr;
 306 +               dst_addr = chan->fifo_addr;
 307 +       } else {
 308 +               src_addr = chan->fifo_addr;
 309 +               dst_addr = sg->addr;
 310 +       }
 311 +       gdma_dma_write(dma_dev, GDMA_REG_SRC_ADDR(chan->id), src_addr);
 312 +       gdma_dma_write(dma_dev, GDMA_REG_DST_ADDR(chan->id), dst_addr);
 313 +       gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL0(chan->id),
 314 +                       (sg->len << GDMA_REG_CTRL0_TX_SHIFT) | GDMA_REG_CTRL0_ENABLE,
 315 +                       GDMA_REG_CTRL0_TX_MASK << GDMA_REG_CTRL0_TX_SHIFT);
 316 +       chan->next_sg++;
 317 +       gdma_dma_write_mask(dma_dev, GDMA_REG_CTRL1(chan->id), 0, GDMA_REG_CTRL1_MASK);
 318 +
 319 +       return 0;
 320 +}
 321 +
 322 +static void gdma_dma_chan_irq(struct gdma_dmaengine_chan *chan)
 323 +{
 324 +       spin_lock(&chan->vchan.lock);
 325 +       if (chan->desc) {
 326 +               if (chan->desc && chan->desc->cyclic) {
 327 +                       vchan_cyclic_callback(&chan->desc->vdesc);
 328 +               } else {
 329 +                       if (chan->next_sg == chan->desc->num_sgs) {
 330 +                               chan->desc = NULL;
 331 +                               vchan_cookie_complete(&chan->desc->vdesc);
 332 +                       }
 333 +               }
 334 +       }
 335 +       gdma_dma_start_transfer(chan);
 336 +       spin_unlock(&chan->vchan.lock);
 337 +}
 338 +
 339 +static irqreturn_t gdma_dma_irq(int irq, void *devid)
 340 +{
 341 +       struct gdma_dma_dev *dma_dev = devid;
 342 +       uint32_t unmask, done;
 343 +       unsigned int i;
 344 +
 345 +       unmask = gdma_dma_read(dma_dev, GDMA_REG_UNMASK_INT);
 346 +       gdma_dma_write(dma_dev, GDMA_REG_UNMASK_INT, unmask);
 347 +       done = gdma_dma_read(dma_dev, GDMA_REG_DONE_INT);
 348 +
 349 +       for (i = 0; i < GDMA_NR_CHANS; ++i)
 350 +               if (done & BIT(i))
 351 +                       gdma_dma_chan_irq(&dma_dev->chan[i]);
 352 +       gdma_dma_write(dma_dev, GDMA_REG_DONE_INT, done);
 353 +
 354 +       return IRQ_HANDLED;
 355 +}
 356 +
 357 +static void gdma_dma_issue_pending(struct dma_chan *c)
 358 +{
 359 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 360 +       unsigned long flags;
 361 +
 362 +       spin_lock_irqsave(&chan->vchan.lock, flags);
 363 +       if (vchan_issue_pending(&chan->vchan) && !chan->desc)
 364 +               gdma_dma_start_transfer(chan);
 365 +       spin_unlock_irqrestore(&chan->vchan.lock, flags);
 366 +}
 367 +
 368 +static struct dma_async_tx_descriptor *gdma_dma_prep_slave_sg(
 369 +       struct dma_chan *c, struct scatterlist *sgl,
 370 +       unsigned int sg_len, enum dma_transfer_direction direction,
 371 +       unsigned long flags, void *context)
 372 +{
 373 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 374 +       struct gdma_dma_desc *desc;
 375 +       struct scatterlist *sg;
 376 +       unsigned int i;
 377 +
 378 +       desc = gdma_dma_alloc_desc(sg_len);
 379 +       if (!desc)
 380 +               return NULL;
 381 +
 382 +       for_each_sg(sgl, sg, sg_len, i) {
 383 +               desc->sg[i].addr = sg_dma_address(sg);
 384 +               desc->sg[i].len = sg_dma_len(sg);
 385 +       }
 386 +
 387 +       desc->num_sgs = sg_len;
 388 +       desc->direction = direction;
 389 +       desc->cyclic = false;
 390 +
 391 +       return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
 392 +}
 393 +
 394 +static struct dma_async_tx_descriptor *gdma_dma_prep_dma_cyclic(
 395 +       struct dma_chan *c, dma_addr_t buf_addr, size_t buf_len,
 396 +       size_t period_len, enum dma_transfer_direction direction,
 397 +       unsigned long flags, void *context)
 398 +{
 399 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 400 +       struct gdma_dma_desc *desc;
 401 +       unsigned int num_periods, i;
 402 +
 403 +       if (buf_len % period_len)
 404 +               return NULL;
 405 +
 406 +       num_periods = buf_len / period_len;
 407 +
 408 +       desc = gdma_dma_alloc_desc(num_periods);
 409 +       if (!desc)
 410 +               return NULL;
 411 +
 412 +       for (i = 0; i < num_periods; i++) {
 413 +               desc->sg[i].addr = buf_addr;
 414 +               desc->sg[i].len = period_len;
 415 +               buf_addr += period_len;
 416 +       }
 417 +
 418 +       desc->num_sgs = num_periods;
 419 +       desc->direction = direction;
 420 +       desc->cyclic = true;
 421 +
 422 +       return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
 423 +}
 424 +
 425 +static size_t gdma_dma_desc_residue(struct gdma_dmaengine_chan *chan,
 426 +       struct gdma_dma_desc *desc, unsigned int next_sg)
 427 +{
 428 +       struct gdma_dma_dev *dma_dev = gdma_dma_chan_get_dev(chan);
 429 +       unsigned int residue, count;
 430 +       unsigned int i;
 431 +
 432 +       residue = 0;
 433 +
 434 +       for (i = next_sg; i < desc->num_sgs; i++)
 435 +               residue += desc->sg[i].len;
 436 +
 437 +       if (next_sg != 0) {
 438 +               count = gdma_dma_read(dma_dev, GDMA_REG_CTRL0(chan->id));
 439 +               count >>= GDMA_REG_CTRL0_CURR_SHIFT;
 440 +               count &= GDMA_REG_CTRL0_CURR_MASK;
 441 +               residue += count << chan->transfer_shift;
 442 +       }
 443 +
 444 +       return residue;
 445 +}
 446 +
 447 +static enum dma_status gdma_dma_tx_status(struct dma_chan *c,
 448 +       dma_cookie_t cookie, struct dma_tx_state *state)
 449 +{
 450 +       struct gdma_dmaengine_chan *chan = to_gdma_dma_chan(c);
 451 +       struct virt_dma_desc *vdesc;
 452 +       enum dma_status status;
 453 +       unsigned long flags;
 454 +
 455 +       status = dma_cookie_status(c, cookie, state);
 456 +       if (status == DMA_SUCCESS || !state)
 457 +               return status;
 458 +
 459 +       spin_lock_irqsave(&chan->vchan.lock, flags);
 460 +       vdesc = vchan_find_desc(&chan->vchan, cookie);
 461 +       if (cookie == chan->desc->vdesc.tx.cookie) {
 462 +               state->residue = gdma_dma_desc_residue(chan, chan->desc,
 463 +                               chan->next_sg);
 464 +       } else if (vdesc) {
 465 +               state->residue = gdma_dma_desc_residue(chan,
 466 +                               to_gdma_dma_desc(vdesc), 0);
 467 +       } else {
 468 +               state->residue = 0;
 469 +       }
 470 +       spin_unlock_irqrestore(&chan->vchan.lock, flags);
 471 +
 472 +       return status;
 473 +}
 474 +
 475 +static int gdma_dma_alloc_chan_resources(struct dma_chan *c)
 476 +{
 477 +       return 0;
 478 +}
 479 +
 480 +static void gdma_dma_free_chan_resources(struct dma_chan *c)
 481 +{
 482 +       vchan_free_chan_resources(to_virt_chan(c));
 483 +}
 484 +
 485 +static void gdma_dma_desc_free(struct virt_dma_desc *vdesc)
 486 +{
 487 +       kfree(container_of(vdesc, struct gdma_dma_desc, vdesc));
 488 +}
 489 +
 490 +static struct dma_chan *
 491 +of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
 492 +                       struct of_dma *ofdma)
 493 +{
 494 +       struct gdma_dma_dev *dma_dev = ofdma->of_dma_data;
 495 +       unsigned int request = dma_spec->args[0];
 496 +
 497 +       if (request >= GDMA_NR_CHANS)
 498 +               return NULL;
 499 +
 500 +       return dma_get_slave_channel(&(dma_dev->chan[request].vchan.chan));
 501 +}
 502 +
 503 +static int gdma_dma_probe(struct platform_device *pdev)
 504 +{
 505 +       struct gdma_dmaengine_chan *chan;
 506 +       struct gdma_dma_dev *dma_dev;
 507 +       struct dma_device *dd;
 508 +       unsigned int i;
 509 +       struct resource *res;
 510 +       uint32_t gct;
 511 +       int ret;
 512 +       int irq;
 513 +
 514 +
 515 +       dma_dev = devm_kzalloc(&pdev->dev, sizeof(*dma_dev), GFP_KERNEL);
 516 +       if (!dma_dev)
 517 +               return -EINVAL;
 518 +
 519 +       dd = &dma_dev->ddev;
 520 +
 521 +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 522 +       dma_dev->base = devm_ioremap_resource(&pdev->dev, res);
 523 +       if (IS_ERR(dma_dev->base))
 524 +               return PTR_ERR(dma_dev->base);
 525 +
 526 +       dma_cap_set(DMA_SLAVE, dd->cap_mask);
 527 +       dma_cap_set(DMA_CYCLIC, dd->cap_mask);
 528 +       dd->device_alloc_chan_resources = gdma_dma_alloc_chan_resources;
 529 +       dd->device_free_chan_resources = gdma_dma_free_chan_resources;
 530 +       dd->device_tx_status = gdma_dma_tx_status;
 531 +       dd->device_issue_pending = gdma_dma_issue_pending;
 532 +       dd->device_prep_slave_sg = gdma_dma_prep_slave_sg;
 533 +       dd->device_prep_dma_cyclic = gdma_dma_prep_dma_cyclic;
 534 +       dd->device_control = gdma_dma_control;
 535 +       dd->dev = &pdev->dev;
 536 +       dd->chancnt = GDMA_NR_CHANS;
 537 +       INIT_LIST_HEAD(&dd->channels);
 538 +
 539 +       for (i = 0; i < dd->chancnt; i++) {
 540 +               chan = &dma_dev->chan[i];
 541 +               chan->id = i;
 542 +               chan->vchan.desc_free = gdma_dma_desc_free;
 543 +               vchan_init(&chan->vchan, dd);
 544 +       }
 545 +
 546 +       ret = dma_async_device_register(dd);
 547 +       if (ret)
 548 +               return ret;
 549 +
 550 +       ret = of_dma_controller_register(pdev->dev.of_node,
 551 +               of_dma_xlate_by_chan_id, dma_dev);
 552 +       if (ret)
 553 +               goto err_unregister;
 554 +
 555 +       irq = platform_get_irq(pdev, 0);
 556 +       ret = request_irq(irq, gdma_dma_irq, 0, dev_name(&pdev->dev), dma_dev);
 557 +       if (ret)
 558 +               goto err_unregister;
 559 +
 560 +       gdma_dma_write(dma_dev, GDMA_REG_UNMASK_INT, 0);
 561 +       gdma_dma_write(dma_dev, GDMA_REG_DONE_INT, BIT(dd->chancnt) - 1);
 562 +
 563 +       gct = gdma_dma_read(dma_dev, GDMA_REG_GCT);
 564 +       dev_info(&pdev->dev, "revision: %d, channels: %d\n",
 565 +               (gct >> GDMA_REG_GCT_VER_SHIFT) & GDMA_REG_GCT_VER_MASK,
 566 +               8 << ((gct >> GDMA_REG_GCT_CHAN_SHIFT) & GDMA_REG_GCT_CHAN_MASK));
 567 +       platform_set_drvdata(pdev, dma_dev);
 568 +
 569 +       gdma_dma_write(dma_dev, GDMA_REG_GCT, GDMA_REG_GCT_ARBIT_RR);
 570 +
 571 +       return 0;
 572 +
 573 +err_unregister:
 574 +       dma_async_device_unregister(dd);
 575 +       return ret;
 576 +}
 577 +
 578 +static int gdma_dma_remove(struct platform_device *pdev)
 579 +{
 580 +       struct gdma_dma_dev *dma_dev = platform_get_drvdata(pdev);
 581 +       int irq = platform_get_irq(pdev, 0);
 582 +
 583 +       free_irq(irq, dma_dev);
 584 +        of_dma_controller_free(pdev->dev.of_node);
 585 +       dma_async_device_unregister(&dma_dev->ddev);
 586 +
 587 +       return 0;
 588 +}
 589 +
 590 +static const struct of_device_id gdma_of_match_table[] = {
 591 +       { .compatible = "ralink,rt2880-gdma" },
 592 +       { },
 593 +};
 594 +
 595 +static struct platform_driver gdma_dma_driver = {
 596 +       .probe = gdma_dma_probe,
 597 +       .remove = gdma_dma_remove,
 598 +       .driver = {
 599 +               .name = "gdma-rt2880",
 600 +               .owner = THIS_MODULE,
 601 +               .of_match_table = gdma_of_match_table,
 602 +       },
 603 +};
 604 +module_platform_driver(gdma_dma_driver);
 605 +
 606 +MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 607 +MODULE_DESCRIPTION("GDMA4740 DMA driver");
 608 +MODULE_LICENSE("GPLv2");
 609 --- a/drivers/dma/dmaengine.c
 610 +++ b/drivers/dma/dmaengine.c
 611 @@ -504,6 +504,32 @@ static struct dma_chan *private_candidat
 612  }
 613
 614  /**
 615 + * dma_request_slave_channel - try to get specific channel exclusively
 616 + * @chan: target channel
 617 + */
 618 +struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
 619 +{
 620 +       int err = -EBUSY;
 621 +
 622 +       /* lock against __dma_request_channel */
 623 +       mutex_lock(&dma_list_mutex);
 624 +
 625 +       if (chan->client_count == 0) {
 626 +               err = dma_chan_get(chan);
 627 +               if (err)
 628 +                       pr_debug("%s: failed to get %s: (%d)\n",
 629 +                               __func__, dma_chan_name(chan), err);
 630 +       } else
 631 +               chan = NULL;
 632 +
 633 +       mutex_unlock(&dma_list_mutex);
 634 +
 635 +       return chan;
 636 +}
 637 +EXPORT_SYMBOL_GPL(dma_get_slave_channel);
 638 +
 639 +
 640 +/**
 641   * dma_request_channel - try to allocate an exclusive channel
 642   * @mask: capabilities that the channel must satisfy
 643   * @fn: optional callback to disposition available channels
 644 --- a/include/linux/dmaengine.h
 645 +++ b/include/linux/dmaengine.h
 646 @@ -999,6 +999,7 @@ static inline void dma_release_channel(s
 647  int dma_async_device_register(struct dma_device *device);
 648  void dma_async_device_unregister(struct dma_device *device);
 649  void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
 650 +struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
 651  struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
 652  struct dma_chan *net_dma_find_channel(void);
 653  #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
 654 --- a/drivers/dma/Makefile
 655 +++ b/drivers/dma/Makefile
 656 @@ -38,3 +38,4 @@ obj-$(CONFIG_DMA_SA11X0) += sa11x0-dma.o
 657  obj-$(CONFIG_MMP_TDMA) += mmp_tdma.o
 658  obj-$(CONFIG_DMA_OMAP) += omap-dma.o
 659  obj-$(CONFIG_MMP_PDMA) += mmp_pdma.o
 660 +obj-$(CONFIG_DMA_RALINK) += ralink-gdma.o