drivers/dma/sun6i-dma.c

/*
 * Copyright (C) 2013-2014 Allwinner Tech Co., Ltd
 * Author: Sugar <shuge@allwinnertech.com>
 *
 * Copyright (C) 2014 Maxime Ripard
 * Maxime Ripard <maxime.ripard@free-electrons.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dmapool.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of_dma.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/reset.h>
#include <linux/slab.h>
#include <linux/types.h>

#include "virt-dma.h"

/*
 * Common registers
 */
#define DMA_IRQ_EN(x)		((x) * 0x04)
#define DMA_IRQ_HALF			BIT(0)
#define DMA_IRQ_PKG			BIT(1)
#define DMA_IRQ_QUEUE			BIT(2)

#define DMA_IRQ_CHAN_NR			8
#define DMA_IRQ_CHAN_WIDTH		4


#define DMA_IRQ_STAT(x)		((x) * 0x04 + 0x10)

#define DMA_STAT		0x30

/*
 * sun8i specific registers
 */
#define SUN8I_DMA_GATE		0x20
#define SUN8I_DMA_GATE_ENABLE	0x4

/*
 * Channels specific registers
 */
#define DMA_CHAN_ENABLE		0x00
#define DMA_CHAN_ENABLE_START		BIT(0)
#define DMA_CHAN_ENABLE_STOP		0

#define DMA_CHAN_PAUSE		0x04
#define DMA_CHAN_PAUSE_PAUSE		BIT(1)
#define DMA_CHAN_PAUSE_RESUME		0

#define DMA_CHAN_LLI_ADDR	0x08

#define DMA_CHAN_CUR_CFG	0x0c
#define DMA_CHAN_CFG_SRC_DRQ(x)		((x) & 0x1f)
#define DMA_CHAN_CFG_SRC_IO_MODE	BIT(5)
#define DMA_CHAN_CFG_SRC_LINEAR_MODE	(0 << 5)
#define DMA_CHAN_CFG_SRC_BURST(x)	(((x) & 0x3) << 7)
#define DMA_CHAN_CFG_SRC_WIDTH(x)	(((x) & 0x3) << 9)

#define DMA_CHAN_CFG_DST_DRQ(x)		(DMA_CHAN_CFG_SRC_DRQ(x) << 16)
#define DMA_CHAN_CFG_DST_IO_MODE	(DMA_CHAN_CFG_SRC_IO_MODE << 16)
#define DMA_CHAN_CFG_DST_LINEAR_MODE	(DMA_CHAN_CFG_SRC_LINEAR_MODE << 16)
#define DMA_CHAN_CFG_DST_BURST(x)	(DMA_CHAN_CFG_SRC_BURST(x) << 16)
#define DMA_CHAN_CFG_DST_WIDTH(x)	(DMA_CHAN_CFG_SRC_WIDTH(x) << 16)

#define DMA_CHAN_CUR_SRC	0x10

#define DMA_CHAN_CUR_DST	0x14

#define DMA_CHAN_CUR_CNT	0x18

#define DMA_CHAN_CUR_PARA	0x1c


/*
 * Various hardware related defines
 */
#define LLI_LAST_ITEM	0xfffff800
#define NORMAL_WAIT	8
#define DRQ_SDRAM	1

/*
 * Hardware channels / ports representation
 *
 * The hardware is used in several SoCs, with differing numbers
 * of channels and endpoints. This structure ties those numbers
 * to a certain compatible string.
 */
struct sun6i_dma_config {
	u32 nr_max_channels;
	u32 nr_max_requests;
	u32 nr_max_vchans;
};

/*
 * Hardware representation of the LLI
 *
 * The hardware will be fed the physical address of this structure,
 * and read its content in order to start the transfer.
 */
struct sun6i_dma_lli {
	u32			cfg;
	u32			src;
	u32			dst;
	u32			len;
	u32			para;
	u32			p_lli_next;

	/*
	 * This field is not used by the DMA controller, but will be
	 * used by the CPU to go through the list (mostly for dumping
	 * or freeing it).
	 */
	struct sun6i_dma_lli	*v_lli_next;
};


struct sun6i_desc {
	struct virt_dma_desc	vd;
	dma_addr_t		p_lli;
	struct sun6i_dma_lli	*v_lli;
};

struct sun6i_pchan {
	u32			idx;
	void __iomem		*base;
	struct sun6i_vchan	*vchan;
	struct sun6i_desc	*desc;
	struct sun6i_desc	*done;
};

struct sun6i_vchan {
	struct virt_dma_chan	vc;
	struct list_head	node;
	struct dma_slave_config	cfg;
	struct sun6i_pchan	*phy;
	u8			port;
};

struct sun6i_dma_dev {
	struct dma_device	slave;
	void __iomem		*base;
	struct clk		*clk;
	int			irq;
	spinlock_t		lock;
	struct reset_control	*rstc;
	struct tasklet_struct	task;
	atomic_t		tasklet_shutdown;
	struct list_head	pending;
	struct dma_pool		*pool;
	struct sun6i_pchan	*pchans;
	struct sun6i_vchan	*vchans;
	const struct sun6i_dma_config *cfg;
};

static struct device *chan2dev(struct dma_chan *chan)
{
	return &chan->dev->device;
}

static inline struct sun6i_dma_dev *to_sun6i_dma_dev(struct dma_device *d)
{
	return container_of(d, struct sun6i_dma_dev, slave);
}

static inline struct sun6i_vchan *to_sun6i_vchan(struct dma_chan *chan)
{
	return container_of(chan, struct sun6i_vchan, vc.chan);
}

static inline struct sun6i_desc *
to_sun6i_desc(struct dma_async_tx_descriptor *tx)
{
	return container_of(tx, struct sun6i_desc, vd.tx);
}

static inline void sun6i_dma_dump_com_regs(struct sun6i_dma_dev *sdev)
{
	dev_dbg(sdev->slave.dev, "Common register:\n"
		"\tmask0(%04x): 0x%08x\n"
		"\tmask1(%04x): 0x%08x\n"
		"\tpend0(%04x): 0x%08x\n"
		"\tpend1(%04x): 0x%08x\n"
		"\tstats(%04x): 0x%08x\n",
		DMA_IRQ_EN(0), readl(sdev->base + DMA_IRQ_EN(0)),
		DMA_IRQ_EN(1), readl(sdev->base + DMA_IRQ_EN(1)),
		DMA_IRQ_STAT(0), readl(sdev->base + DMA_IRQ_STAT(0)),
		DMA_IRQ_STAT(1), readl(sdev->base + DMA_IRQ_STAT(1)),
		DMA_STAT, readl(sdev->base + DMA_STAT));
}

static inline void sun6i_dma_dump_chan_regs(struct sun6i_dma_dev *sdev,
					    struct sun6i_pchan *pchan)
{
	phys_addr_t reg = virt_to_phys(pchan->base);

	dev_dbg(sdev->slave.dev, "Chan %d reg: %pa\n"
		"\t___en(%04x): \t0x%08x\n"
		"\tpause(%04x): \t0x%08x\n"
		"\tstart(%04x): \t0x%08x\n"
		"\t__cfg(%04x): \t0x%08x\n"
		"\t__src(%04x): \t0x%08x\n"
		"\t__dst(%04x): \t0x%08x\n"
		"\tcount(%04x): \t0x%08x\n"
		"\t_para(%04x): \t0x%08x\n\n",
		pchan->idx, &reg,
		DMA_CHAN_ENABLE,
		readl(pchan->base + DMA_CHAN_ENABLE),
		DMA_CHAN_PAUSE,
		readl(pchan->base + DMA_CHAN_PAUSE),
		DMA_CHAN_LLI_ADDR,
		readl(pchan->base + DMA_CHAN_LLI_ADDR),
		DMA_CHAN_CUR_CFG,
		readl(pchan->base + DMA_CHAN_CUR_CFG),
		DMA_CHAN_CUR_SRC,
		readl(pchan->base + DMA_CHAN_CUR_SRC),
		DMA_CHAN_CUR_DST,
		readl(pchan->base + DMA_CHAN_CUR_DST),
		DMA_CHAN_CUR_CNT,
		readl(pchan->base + DMA_CHAN_CUR_CNT),
		DMA_CHAN_CUR_PARA,
		readl(pchan->base + DMA_CHAN_CUR_PARA));
}

static inline int convert_burst(u32 maxburst, u8 *burst)
{
	switch (maxburst) {
	case 1:
		*burst = 0;
		break;
	case 8:
		*burst = 2;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static inline int convert_buswidth(enum dma_slave_buswidth addr_width, u8 *width)
{
	if ((addr_width < DMA_SLAVE_BUSWIDTH_1_BYTE) ||
	    (addr_width > DMA_SLAVE_BUSWIDTH_4_BYTES))
		return -EINVAL;

	*width = addr_width >> 1;
	return 0;
}

static void *sun6i_dma_lli_add(struct sun6i_dma_lli *prev,
			       struct sun6i_dma_lli *next,
			       dma_addr_t next_phy,
			       struct sun6i_desc *txd)
{
	if ((!prev && !txd) || !next)
		return NULL;

	if (!prev) {
		txd->p_lli = next_phy;
		txd->v_lli = next;
	} else {
		prev->p_lli_next = next_phy;
		prev->v_lli_next = next;
	}

	next->p_lli_next = LLI_LAST_ITEM;
	next->v_lli_next = NULL;

	return next;
}

static inline int sun6i_dma_cfg_lli(struct sun6i_dma_lli *lli,
				    dma_addr_t src,
				    dma_addr_t dst, u32 len,
				    struct dma_slave_config *config)
{
	u8 src_width, dst_width, src_burst, dst_burst;
	int ret;

	if (!config)
		return -EINVAL;

	ret = convert_burst(config->src_maxburst, &src_burst);
	if (ret)
		return ret;

	ret = convert_burst(config->dst_maxburst, &dst_burst);
	if (ret)
		return ret;

	ret = convert_buswidth(config->src_addr_width, &src_width);
	if (ret)
		return ret;

	ret = convert_buswidth(config->dst_addr_width, &dst_width);
	if (ret)
		return ret;

	lli->cfg = DMA_CHAN_CFG_SRC_BURST(src_burst) |
		DMA_CHAN_CFG_SRC_WIDTH(src_width) |
		DMA_CHAN_CFG_DST_BURST(dst_burst) |
		DMA_CHAN_CFG_DST_WIDTH(dst_width);

	lli->src = src;
	lli->dst = dst;
	lli->len = len;
	lli->para = NORMAL_WAIT;

	return 0;
}

static inline void sun6i_dma_dump_lli(struct sun6i_vchan *vchan,
				      struct sun6i_dma_lli *lli)
{
	phys_addr_t p_lli = virt_to_phys(lli);

	dev_dbg(chan2dev(&vchan->vc.chan),
		"\n\tdesc:   p - %pa v - 0x%p\n"
		"\t\tc - 0x%08x s - 0x%08x d - 0x%08x\n"
		"\t\tl - 0x%08x p - 0x%08x n - 0x%08x\n",
		&p_lli, lli,
		lli->cfg, lli->src, lli->dst,
		lli->len, lli->para, lli->p_lli_next);
}

static void sun6i_dma_free_desc(struct virt_dma_desc *vd)
{
	struct sun6i_desc *txd = to_sun6i_desc(&vd->tx);
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(vd->tx.chan->device);
	struct sun6i_dma_lli *v_lli, *v_next;
	dma_addr_t p_lli, p_next;

	if (unlikely(!txd))
		return;

	p_lli = txd->p_lli;
	v_lli = txd->v_lli;

	while (v_lli) {
		v_next = v_lli->v_lli_next;
		p_next = v_lli->p_lli_next;

		dma_pool_free(sdev->pool, v_lli, p_lli);

		v_lli = v_next;
		p_lli = p_next;
	}

	kfree(txd);
}

static int sun6i_dma_terminate_all(struct sun6i_vchan *vchan)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(vchan->vc.chan.device);
	struct sun6i_pchan *pchan = vchan->phy;
	unsigned long flags;
	LIST_HEAD(head);

	spin_lock(&sdev->lock);
	list_del_init(&vchan->node);
	spin_unlock(&sdev->lock);

	spin_lock_irqsave(&vchan->vc.lock, flags);

	vchan_get_all_descriptors(&vchan->vc, &head);

	if (pchan) {
		writel(DMA_CHAN_ENABLE_STOP, pchan->base + DMA_CHAN_ENABLE);
		writel(DMA_CHAN_PAUSE_RESUME, pchan->base + DMA_CHAN_PAUSE);

		vchan->phy = NULL;
		pchan->vchan = NULL;
		pchan->desc = NULL;
		pchan->done = NULL;
	}

	spin_unlock_irqrestore(&vchan->vc.lock, flags);

	vchan_dma_desc_free_list(&vchan->vc, &head);

	return 0;
}

static int sun6i_dma_start_desc(struct sun6i_vchan *vchan)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(vchan->vc.chan.device);
	struct virt_dma_desc *desc = vchan_next_desc(&vchan->vc);
	struct sun6i_pchan *pchan = vchan->phy;
	u32 irq_val, irq_reg, irq_offset;

	if (!pchan)
		return -EAGAIN;

	if (!desc) {
		pchan->desc = NULL;
		pchan->done = NULL;
		return -EAGAIN;
	}

	list_del(&desc->node);

	pchan->desc = to_sun6i_desc(&desc->tx);
	pchan->done = NULL;

	sun6i_dma_dump_lli(vchan, pchan->desc->v_lli);

	irq_reg = pchan->idx / DMA_IRQ_CHAN_NR;
	irq_offset = pchan->idx % DMA_IRQ_CHAN_NR;

	irq_val = readl(sdev->base + DMA_IRQ_EN(irq_offset));
	irq_val |= DMA_IRQ_QUEUE << (irq_offset * DMA_IRQ_CHAN_WIDTH);
	writel(irq_val, sdev->base + DMA_IRQ_EN(irq_offset));

	writel(pchan->desc->p_lli, pchan->base + DMA_CHAN_LLI_ADDR);
	writel(DMA_CHAN_ENABLE_START, pchan->base + DMA_CHAN_ENABLE);

	sun6i_dma_dump_com_regs(sdev);
	sun6i_dma_dump_chan_regs(sdev, pchan);

	return 0;
}

static void sun6i_dma_tasklet(unsigned long data)
{
	struct sun6i_dma_dev *sdev = (struct sun6i_dma_dev *)data;
	const struct sun6i_dma_config *cfg = sdev->cfg;
	struct sun6i_vchan *vchan;
	struct sun6i_pchan *pchan;
	unsigned int pchan_alloc = 0;
	unsigned int pchan_idx;

	list_for_each_entry(vchan, &sdev->slave.channels, vc.chan.device_node) {
		spin_lock_irq(&vchan->vc.lock);

		pchan = vchan->phy;

		if (pchan && pchan->done) {
			if (sun6i_dma_start_desc(vchan)) {
				/*
				 * No current txd associated with this channel
				 */
				dev_dbg(sdev->slave.dev, "pchan %u: free\n",
					pchan->idx);

				/* Mark this channel free */
				vchan->phy = NULL;
				pchan->vchan = NULL;
			}
		}
		spin_unlock_irq(&vchan->vc.lock);
	}

	spin_lock_irq(&sdev->lock);
	for (pchan_idx = 0; pchan_idx < cfg->nr_max_channels; pchan_idx++) {
		pchan = &sdev->pchans[pchan_idx];

		if (pchan->vchan || list_empty(&sdev->pending))
			continue;

		vchan = list_first_entry(&sdev->pending,
					 struct sun6i_vchan, node);

		/* Remove from pending channels */
		list_del_init(&vchan->node);
		pchan_alloc |= BIT(pchan_idx);

		/* Mark this channel allocated */
		pchan->vchan = vchan;
		vchan->phy = pchan;
		dev_dbg(sdev->slave.dev, "pchan %u: alloc vchan %p\n",
			pchan->idx, &vchan->vc);
	}
	spin_unlock_irq(&sdev->lock);

	for (pchan_idx = 0; pchan_idx < cfg->nr_max_channels; pchan_idx++) {
		if (!(pchan_alloc & BIT(pchan_idx)))
			continue;

		pchan = sdev->pchans + pchan_idx;
		vchan = pchan->vchan;
		if (vchan) {
			spin_lock_irq(&vchan->vc.lock);
			sun6i_dma_start_desc(vchan);
			spin_unlock_irq(&vchan->vc.lock);
		}
	}
}

static irqreturn_t sun6i_dma_interrupt(int irq, void *dev_id)
{
	struct sun6i_dma_dev *sdev = dev_id;
	struct sun6i_vchan *vchan;
	struct sun6i_pchan *pchan;
	int i, j, ret = IRQ_NONE;
	u32 status;

	for (i = 0; i < sdev->cfg->nr_max_channels / DMA_IRQ_CHAN_NR; i++) {
		status = readl(sdev->base + DMA_IRQ_STAT(i));
		if (!status)
			continue;

		dev_dbg(sdev->slave.dev, "DMA irq status %s: 0x%x\n",
			i ? "high" : "low", status);

		writel(status, sdev->base + DMA_IRQ_STAT(i));

		for (j = 0; (j < DMA_IRQ_CHAN_NR) && status; j++) {
			if (status & DMA_IRQ_QUEUE) {
				pchan = sdev->pchans + j;
				vchan = pchan->vchan;

				if (vchan) {
					spin_lock(&vchan->vc.lock);
					vchan_cookie_complete(&pchan->desc->vd);
					pchan->done = pchan->desc;
					spin_unlock(&vchan->vc.lock);
				}
			}

			status = status >> DMA_IRQ_CHAN_WIDTH;
		}

		if (!atomic_read(&sdev->tasklet_shutdown))
			tasklet_schedule(&sdev->task);
		ret = IRQ_HANDLED;
	}

	return ret;
}

static struct dma_async_tx_descriptor *sun6i_dma_prep_dma_memcpy(
		struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
		size_t len, unsigned long flags)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	struct dma_slave_config *sconfig = &vchan->cfg;
	struct sun6i_dma_lli *v_lli;
	struct sun6i_desc *txd;
	dma_addr_t p_lli;
	int ret;

	dev_dbg(chan2dev(chan),
		"%s; chan: %d, dest: %pad, src: %pad, len: %zu. flags: 0x%08lx\n",
		__func__, vchan->vc.chan.chan_id, &dest, &src, len, flags);

	if (!len)
		return NULL;

	txd = kzalloc(sizeof(*txd), GFP_NOWAIT);
	if (!txd)
		return NULL;

	v_lli = dma_pool_alloc(sdev->pool, GFP_NOWAIT, &p_lli);
	if (!v_lli) {
		dev_err(sdev->slave.dev, "Failed to alloc lli memory\n");
		goto err_txd_free;
	}

	ret = sun6i_dma_cfg_lli(v_lli, src, dest, len, sconfig);
	if (ret)
		goto err_dma_free;

	v_lli->cfg |= DMA_CHAN_CFG_SRC_DRQ(DRQ_SDRAM) |
		DMA_CHAN_CFG_DST_DRQ(DRQ_SDRAM) |
		DMA_CHAN_CFG_DST_LINEAR_MODE |
		DMA_CHAN_CFG_SRC_LINEAR_MODE;

	sun6i_dma_lli_add(NULL, v_lli, p_lli, txd);

	sun6i_dma_dump_lli(vchan, v_lli);

	return vchan_tx_prep(&vchan->vc, &txd->vd, flags);

err_dma_free:
	dma_pool_free(sdev->pool, v_lli, p_lli);
err_txd_free:
	kfree(txd);
	return NULL;
}

static struct dma_async_tx_descriptor *sun6i_dma_prep_slave_sg(
		struct dma_chan *chan, struct scatterlist *sgl,
		unsigned int sg_len, enum dma_transfer_direction dir,
		unsigned long flags, void *context)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	struct dma_slave_config *sconfig = &vchan->cfg;
	struct sun6i_dma_lli *v_lli, *prev = NULL;
	struct sun6i_desc *txd;
	struct scatterlist *sg;
	dma_addr_t p_lli;
	int i, ret;

	if (!sgl)
		return NULL;

	if (!is_slave_direction(dir)) {
		dev_err(chan2dev(chan), "Invalid DMA direction\n");
		return NULL;
	}

	txd = kzalloc(sizeof(*txd), GFP_NOWAIT);
	if (!txd)
		return NULL;

	for_each_sg(sgl, sg, sg_len, i) {
		v_lli = dma_pool_alloc(sdev->pool, GFP_NOWAIT, &p_lli);
		if (!v_lli)
			goto err_lli_free;

		if (dir == DMA_MEM_TO_DEV) {
			ret = sun6i_dma_cfg_lli(v_lli, sg_dma_address(sg),
						sconfig->dst_addr, sg_dma_len(sg),
						sconfig);
			if (ret)
				goto err_cur_lli_free;

			v_lli->cfg |= DMA_CHAN_CFG_DST_IO_MODE |
				DMA_CHAN_CFG_SRC_LINEAR_MODE |
				DMA_CHAN_CFG_SRC_DRQ(DRQ_SDRAM) |
				DMA_CHAN_CFG_DST_DRQ(vchan->port);

			dev_dbg(chan2dev(chan),
				"%s; chan: %d, dest: %pad, src: %pad, len: %u. flags: 0x%08lx\n",
				__func__, vchan->vc.chan.chan_id,
				&sconfig->dst_addr, &sg_dma_address(sg),
				sg_dma_len(sg), flags);

		} else {
			ret = sun6i_dma_cfg_lli(v_lli, sconfig->src_addr,
						sg_dma_address(sg), sg_dma_len(sg),
						sconfig);
			if (ret)
				goto err_cur_lli_free;

			v_lli->cfg |= DMA_CHAN_CFG_DST_LINEAR_MODE |
				DMA_CHAN_CFG_SRC_IO_MODE |
				DMA_CHAN_CFG_DST_DRQ(DRQ_SDRAM) |
				DMA_CHAN_CFG_SRC_DRQ(vchan->port);

			dev_dbg(chan2dev(chan),
				"%s; chan: %d, dest: %pad, src: %pad, len: %u. flags: 0x%08lx\n",
				__func__, vchan->vc.chan.chan_id,
				&sg_dma_address(sg), &sconfig->src_addr,
				sg_dma_len(sg), flags);
		}

		prev = sun6i_dma_lli_add(prev, v_lli, p_lli, txd);
	}

	dev_dbg(chan2dev(chan), "First: %pad\n", &txd->p_lli);
	for (prev = txd->v_lli; prev; prev = prev->v_lli_next)
		sun6i_dma_dump_lli(vchan, prev);

	return vchan_tx_prep(&vchan->vc, &txd->vd, flags);

err_cur_lli_free:
	dma_pool_free(sdev->pool, v_lli, p_lli);
err_lli_free:
	for (prev = txd->v_lli; prev; prev = prev->v_lli_next)
		dma_pool_free(sdev->pool, prev, virt_to_phys(prev));
	kfree(txd);
	return NULL;
}

static int sun6i_dma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
		       unsigned long arg)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	struct sun6i_pchan *pchan = vchan->phy;
	unsigned long flags;
	int ret = 0;

	switch (cmd) {
	case DMA_RESUME:
		dev_dbg(chan2dev(chan), "vchan %p: resume\n", &vchan->vc);

		spin_lock_irqsave(&vchan->vc.lock, flags);

		if (pchan) {
			writel(DMA_CHAN_PAUSE_RESUME,
			       pchan->base + DMA_CHAN_PAUSE);
		} else if (!list_empty(&vchan->vc.desc_issued)) {
			spin_lock(&sdev->lock);
			list_add_tail(&vchan->node, &sdev->pending);
			spin_unlock(&sdev->lock);
		}

		spin_unlock_irqrestore(&vchan->vc.lock, flags);
		break;

	case DMA_PAUSE:
		dev_dbg(chan2dev(chan), "vchan %p: pause\n", &vchan->vc);

		if (pchan) {
			writel(DMA_CHAN_PAUSE_PAUSE,
			       pchan->base + DMA_CHAN_PAUSE);
		} else {
			spin_lock(&sdev->lock);
			list_del_init(&vchan->node);
			spin_unlock(&sdev->lock);
		}
		break;

	case DMA_TERMINATE_ALL:
		ret = sun6i_dma_terminate_all(vchan);
		break;
	case DMA_SLAVE_CONFIG:
		memcpy(&vchan->cfg, (void *)arg, sizeof(struct dma_slave_config));
		break;
	default:
		ret = -ENXIO;
		break;
	}
	return ret;
}

static enum dma_status sun6i_dma_tx_status(struct dma_chan *chan,
					   dma_cookie_t cookie,
					   struct dma_tx_state *state)
{
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	struct sun6i_pchan *pchan = vchan->phy;
	struct sun6i_dma_lli *lli;
	struct virt_dma_desc *vd;
	struct sun6i_desc *txd;
	enum dma_status ret;
	unsigned long flags;
	size_t bytes = 0;

	ret = dma_cookie_status(chan, cookie, state);
	if (ret == DMA_COMPLETE)
		return ret;

	spin_lock_irqsave(&vchan->vc.lock, flags);

	vd = vchan_find_desc(&vchan->vc, cookie);
	txd = to_sun6i_desc(&vd->tx);

	if (vd) {
		for (lli = txd->v_lli; lli != NULL; lli = lli->v_lli_next)
			bytes += lli->len;
	} else if (!pchan || !pchan->desc) {
		bytes = 0;
	} else {
		bytes = readl(pchan->base + DMA_CHAN_CUR_CNT);
	}

	spin_unlock_irqrestore(&vchan->vc.lock, flags);

	dma_set_residue(state, bytes);

	return ret;
}

static void sun6i_dma_issue_pending(struct dma_chan *chan)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	unsigned long flags;

	spin_lock_irqsave(&vchan->vc.lock, flags);

	if (vchan_issue_pending(&vchan->vc)) {
		spin_lock(&sdev->lock);

		if (!vchan->phy && list_empty(&vchan->node)) {
			list_add_tail(&vchan->node, &sdev->pending);
			tasklet_schedule(&sdev->task);
			dev_dbg(chan2dev(chan), "vchan %p: issued\n",
				&vchan->vc);
		}

		spin_unlock(&sdev->lock);
	} else {
		dev_dbg(chan2dev(chan), "vchan %p: nothing to issue\n",
			&vchan->vc);
	}

	spin_unlock_irqrestore(&vchan->vc.lock, flags);
}

static int sun6i_dma_alloc_chan_resources(struct dma_chan *chan)
{
	return 0;
}

static void sun6i_dma_free_chan_resources(struct dma_chan *chan)
{
	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
	unsigned long flags;

	spin_lock_irqsave(&sdev->lock, flags);
	list_del_init(&vchan->node);
	spin_unlock_irqrestore(&sdev->lock, flags);

	vchan_free_chan_resources(&vchan->vc);
}

static struct dma_chan *sun6i_dma_of_xlate(struct of_phandle_args *dma_spec,
					   struct of_dma *ofdma)
{
	struct sun6i_dma_dev *sdev = ofdma->of_dma_data;
	struct sun6i_vchan *vchan;
	struct dma_chan *chan;
	u8 port = dma_spec->args[0];

	if (port > sdev->cfg->nr_max_requests)
		return NULL;

	chan = dma_get_any_slave_channel(&sdev->slave);
	if (!chan)
		return NULL;

	vchan = to_sun6i_vchan(chan);
	vchan->port = port;

	return chan;
}

static inline void sun6i_kill_tasklet(struct sun6i_dma_dev *sdev)
{
	/* Disable all interrupts from DMA */
	writel(0, sdev->base + DMA_IRQ_EN(0));
	writel(0, sdev->base + DMA_IRQ_EN(1));

	/* Prevent spurious interrupts from scheduling the tasklet */
	atomic_inc(&sdev->tasklet_shutdown);

	/* Make sure we won't have any further interrupts */
	devm_free_irq(sdev->slave.dev, sdev->irq, sdev);

	/* Actually prevent the tasklet from being scheduled */
	tasklet_kill(&sdev->task);
}

static inline void sun6i_dma_free(struct sun6i_dma_dev *sdev)
{
	int i;

	for (i = 0; i < sdev->cfg->nr_max_vchans; i++) {
		struct sun6i_vchan *vchan = &sdev->vchans[i];

		list_del(&vchan->vc.chan.device_node);
		tasklet_kill(&vchan->vc.task);
	}
}

/*
 * For A31:
 *
 * There's 16 physical channels that can work in parallel.
 *
 * However we have 30 different endpoints for our requests.
 *
 * Since the channels are able to handle only an unidirectional
 * transfer, we need to allocate more virtual channels so that
 * everyone can grab one channel.
 *
 * Some devices can't work in both direction (mostly because it
 * wouldn't make sense), so we have a bit fewer virtual channels than
 * 2 channels per endpoints.
 */

static struct sun6i_dma_config sun6i_a31_dma_cfg = {
	.nr_max_channels = 16,
	.nr_max_requests = 30,
	.nr_max_vchans   = 53,
};

/*
 * The A23 only has 8 physical channels, a maximum DRQ port id of 24,
 * and a total of 37 usable source and destination endpoints.
 */

static struct sun6i_dma_config sun8i_a23_dma_cfg = {
	.nr_max_channels = 8,
	.nr_max_requests = 24,
	.nr_max_vchans   = 37,
};

static struct of_device_id sun6i_dma_match[] = {
	{ .compatible = "allwinner,sun6i-a31-dma", .data = &sun6i_a31_dma_cfg },
	{ .compatible = "allwinner,sun8i-a23-dma", .data = &sun8i_a23_dma_cfg },
	{ /* sentinel */ }
};

static int sun6i_dma_probe(struct platform_device *pdev)
{
	const struct of_device_id *device;
	struct sun6i_dma_dev *sdc;
	struct resource *res;
	int ret, i;

	sdc = devm_kzalloc(&pdev->dev, sizeof(*sdc), GFP_KERNEL);
	if (!sdc)
		return -ENOMEM;

	device = of_match_device(sun6i_dma_match, &pdev->dev);
	if (!device)
		return -ENODEV;
	sdc->cfg = device->data;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	sdc->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(sdc->base))
		return PTR_ERR(sdc->base);

	sdc->irq = platform_get_irq(pdev, 0);
	if (sdc->irq < 0) {
		dev_err(&pdev->dev, "Cannot claim IRQ\n");
		return sdc->irq;
	}

	sdc->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(sdc->clk)) {
		dev_err(&pdev->dev, "No clock specified\n");
		return PTR_ERR(sdc->clk);
	}

	sdc->rstc = devm_reset_control_get(&pdev->dev, NULL);
	if (IS_ERR(sdc->rstc)) {
		dev_err(&pdev->dev, "No reset controller specified\n");
		return PTR_ERR(sdc->rstc);
	}

	sdc->pool = dmam_pool_create(dev_name(&pdev->dev), &pdev->dev,
				     sizeof(struct sun6i_dma_lli), 4, 0);
	if (!sdc->pool) {
		dev_err(&pdev->dev, "No memory for descriptors dma pool\n");
		return -ENOMEM;
	}

	platform_set_drvdata(pdev, sdc);
	INIT_LIST_HEAD(&sdc->pending);
	spin_lock_init(&sdc->lock);

	dma_cap_set(DMA_PRIVATE, sdc->slave.cap_mask);
	dma_cap_set(DMA_MEMCPY, sdc->slave.cap_mask);
	dma_cap_set(DMA_SLAVE, sdc->slave.cap_mask);

	INIT_LIST_HEAD(&sdc->slave.channels);
	sdc->slave.device_alloc_chan_resources	= sun6i_dma_alloc_chan_resources;
	sdc->slave.device_free_chan_resources	= sun6i_dma_free_chan_resources;
	sdc->slave.device_tx_status		= sun6i_dma_tx_status;
	sdc->slave.device_issue_pending		= sun6i_dma_issue_pending;
	sdc->slave.device_prep_slave_sg		= sun6i_dma_prep_slave_sg;
	sdc->slave.device_prep_dma_memcpy	= sun6i_dma_prep_dma_memcpy;
	sdc->slave.device_control		= sun6i_dma_control;

	sdc->slave.dev = &pdev->dev;

	sdc->pchans = devm_kcalloc(&pdev->dev, sdc->cfg->nr_max_channels,
				   sizeof(struct sun6i_pchan), GFP_KERNEL);
	if (!sdc->pchans)
		return -ENOMEM;

	sdc->vchans = devm_kcalloc(&pdev->dev, sdc->cfg->nr_max_vchans,
				   sizeof(struct sun6i_vchan), GFP_KERNEL);
	if (!sdc->vchans)
		return -ENOMEM;

	tasklet_init(&sdc->task, sun6i_dma_tasklet, (unsigned long)sdc);

	for (i = 0; i < sdc->cfg->nr_max_channels; i++) {
		struct sun6i_pchan *pchan = &sdc->pchans[i];

		pchan->idx = i;
		pchan->base = sdc->base + 0x100 + i * 0x40;
	}

	for (i = 0; i < sdc->cfg->nr_max_vchans; i++) {
		struct sun6i_vchan *vchan = &sdc->vchans[i];

		INIT_LIST_HEAD(&vchan->node);
		vchan->vc.desc_free = sun6i_dma_free_desc;
		vchan_init(&vchan->vc, &sdc->slave);
	}

	ret = reset_control_deassert(sdc->rstc);
	if (ret) {
		dev_err(&pdev->dev, "Couldn't deassert the device from reset\n");
		goto err_chan_free;
	}

	ret = clk_prepare_enable(sdc->clk);
	if (ret) {
		dev_err(&pdev->dev, "Couldn't enable the clock\n");
		goto err_reset_assert;
	}

	ret = devm_request_irq(&pdev->dev, sdc->irq, sun6i_dma_interrupt, 0,
			       dev_name(&pdev->dev), sdc);
	if (ret) {
		dev_err(&pdev->dev, "Cannot request IRQ\n");
		goto err_clk_disable;
	}

	ret = dma_async_device_register(&sdc->slave);
	if (ret) {
		dev_warn(&pdev->dev, "Failed to register DMA engine device\n");
		goto err_irq_disable;
	}

	ret = of_dma_controller_register(pdev->dev.of_node, sun6i_dma_of_xlate,
					 sdc);
	if (ret) {
		dev_err(&pdev->dev, "of_dma_controller_register failed\n");
		goto err_dma_unregister;
	}

	/*
	 * sun8i variant requires us to toggle a dma gating register,
	 * as seen in Allwinner's SDK. This register is not documented
	 * in the A23 user manual.
	 */
	if (of_device_is_compatible(pdev->dev.of_node,
				    "allwinner,sun8i-a23-dma"))
		writel(SUN8I_DMA_GATE_ENABLE, sdc->base + SUN8I_DMA_GATE);

	return 0;

err_dma_unregister:
	dma_async_device_unregister(&sdc->slave);
err_irq_disable:
	sun6i_kill_tasklet(sdc);
err_clk_disable:
	clk_disable_unprepare(sdc->clk);
err_reset_assert:
	reset_control_assert(sdc->rstc);
err_chan_free:
	sun6i_dma_free(sdc);
	return ret;
}

static int sun6i_dma_remove(struct platform_device *pdev)
{
	struct sun6i_dma_dev *sdc = platform_get_drvdata(pdev);

	of_dma_controller_free(pdev->dev.of_node);
	dma_async_device_unregister(&sdc->slave);

	sun6i_kill_tasklet(sdc);

	clk_disable_unprepare(sdc->clk);
	reset_control_assert(sdc->rstc);

	sun6i_dma_free(sdc);

	return 0;
}

static struct platform_driver sun6i_dma_driver = {
	.probe		= sun6i_dma_probe,
	.remove		= sun6i_dma_remove,
	.driver = {
		.name		= "sun6i-dma",
		.of_match_table	= sun6i_dma_match,
	},
};
module_platform_driver(sun6i_dma_driver);

MODULE_DESCRIPTION("Allwinner A31 DMA Controller Driver");
MODULE_AUTHOR("Sugar <shuge@allwinnertech.com>");
MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
MODULE_LICENSE("GPL");