dma: add mxs-apbh-dma driver

Based on the U-Boot version. Changed to kernel style register layout, added
MX23 support, made MMU aware and adapted to barebox.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mxs/include/mach/dma.h

@@ -0,0 +1,145 @@
+/*
+ * Freescale i.MX28 APBH DMA
+ *
+ * Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
+ * on behalf of DENX Software Engineering GmbH
+ *
+ * Based on code from LTIB:
+ * Copyright 2008-2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
+
+#ifndef __DMA_H__
+#define __DMA_H__
+
+#include <linux/list.h>
+
+#ifndef	CONFIG_ARCH_DMA_PIO_WORDS
+#define	DMA_PIO_WORDS		15
+#else
+#define	DMA_PIO_WORDS		CONFIG_ARCH_DMA_PIO_WORDS
+#endif
+
+#define MXS_DMA_ALIGNMENT	32
+
+/*
+ * MXS DMA channels
+ */
+enum {
+	MXS_DMA_CHANNEL_AHB_APBH_SSP0 = 0,
+	MXS_DMA_CHANNEL_AHB_APBH_SSP1,
+	MXS_DMA_CHANNEL_AHB_APBH_SSP2,
+	MXS_DMA_CHANNEL_AHB_APBH_SSP3,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI0,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI1,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI2,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI3,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI4,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI5,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI6,
+	MXS_DMA_CHANNEL_AHB_APBH_GPMI7,
+	MXS_DMA_CHANNEL_AHB_APBH_SSP,
+	MXS_MAX_DMA_CHANNELS,
+};
+
+/*
+ * MXS DMA hardware command.
+ *
+ * This structure describes the in-memory layout of an entire DMA command,
+ * including space for the maximum number of PIO accesses. See the appropriate
+ * reference manual for a detailed description of what these fields mean to the
+ * DMA hardware.
+ */
+#define	MXS_DMA_DESC_COMMAND_MASK	0x3
+#define	MXS_DMA_DESC_COMMAND_OFFSET	0
+#define	MXS_DMA_DESC_COMMAND_NO_DMAXFER	0x0
+#define	MXS_DMA_DESC_COMMAND_DMA_WRITE	0x1
+#define	MXS_DMA_DESC_COMMAND_DMA_READ	0x2
+#define	MXS_DMA_DESC_COMMAND_DMA_SENSE	0x3
+#define	MXS_DMA_DESC_CHAIN		(1 << 2)
+#define	MXS_DMA_DESC_IRQ		(1 << 3)
+#define	MXS_DMA_DESC_NAND_LOCK		(1 << 4)
+#define	MXS_DMA_DESC_NAND_WAIT_4_READY	(1 << 5)
+#define	MXS_DMA_DESC_DEC_SEM		(1 << 6)
+#define	MXS_DMA_DESC_WAIT4END		(1 << 7)
+#define	MXS_DMA_DESC_HALT_ON_TERMINATE	(1 << 8)
+#define	MXS_DMA_DESC_TERMINATE_FLUSH	(1 << 9)
+#define	MXS_DMA_DESC_PIO_WORDS_MASK	(0xf << 12)
+#define	MXS_DMA_DESC_PIO_WORDS_OFFSET	12
+#define	MXS_DMA_DESC_BYTES_MASK		(0xffff << 16)
+#define	MXS_DMA_DESC_BYTES_OFFSET	16
+
+struct mxs_dma_cmd {
+	unsigned long		next;
+	unsigned long		data;
+	union {
+		dma_addr_t	address;
+		unsigned long	alternate;
+	};
+	unsigned long		pio_words[DMA_PIO_WORDS];
+};
+
+/*
+ * MXS DMA command descriptor.
+ *
+ * This structure incorporates an MXS DMA hardware command structure, along
+ * with metadata.
+ */
+#define	MXS_DMA_DESC_FIRST	(1 << 0)
+#define	MXS_DMA_DESC_LAST	(1 << 1)
+#define	MXS_DMA_DESC_READY	(1 << 31)
+
+struct mxs_dma_desc {
+	struct mxs_dma_cmd	cmd;
+	unsigned int		flags;
+	dma_addr_t		address;
+	void			*buffer;
+	struct list_head	node;
+};
+
+/**
+ * MXS DMA channel
+ *
+ * This structure represents a single DMA channel. The MXS platform code
+ * maintains an array of these structures to represent every DMA channel in the
+ * system (see mxs_dma_channels).
+ */
+#define	MXS_DMA_FLAGS_IDLE	0
+#define	MXS_DMA_FLAGS_BUSY	(1 << 0)
+#define	MXS_DMA_FLAGS_FREE	0
+#define	MXS_DMA_FLAGS_ALLOCATED	(1 << 16)
+#define	MXS_DMA_FLAGS_VALID	(1 << 31)
+
+struct mxs_dma_chan {
+	const char *name;
+	unsigned long dev;
+	struct mxs_dma_device *dma;
+	unsigned int flags;
+	unsigned int active_num;
+	unsigned int pending_num;
+	struct list_head active;
+	struct list_head done;
+};
+
+struct mxs_dma_desc *mxs_dma_desc_alloc(void);
+void mxs_dma_desc_free(struct mxs_dma_desc *);
+int mxs_dma_desc_append(int channel, struct mxs_dma_desc *pdesc);
+
+int mxs_dma_go(int chan);
+int mxs_dma_init(void);
+
+#endif	/* __DMA_H__ */

drivers/Kconfig

@@ -17,5 +17,6 @@ source "drivers/eeprom/Kconfig"
 source "drivers/input/Kconfig"
 
 source "drivers/pwm/Kconfig"
+source "drivers/dma/Kconfig"
 
 endmenu

drivers/Makefile

@@ -15,3 +15,4 @@ obj-$(CONFIG_LED) += led/
 obj-y	+= eeprom/
 obj-$(CONFIG_PWM) += pwm/
 obj-y	+= input/
+obj-y	+= dma/

drivers/dma/Kconfig

@@ -0,0 +1,8 @@
+menu "DMA support"
+
+config MXS_APBH_DMA
+	tristate "MXS APBH DMA ENGINE"
+	depends on ARCH_IMX23 || ARCH_IMX28
+	help
+	Experimental!
+endmenu

drivers/dma/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_MXS_APBH_DMA)	+= apbh_dma.o

drivers/dma/apbh_dma.c

@@ -0,0 +1,598 @@
+/*
+ * Freescale i.MX28 APBH DMA driver
+ *
+ * Copyright (C) 2011 Wolfram Sang <w.sang@pengutronix.de>
+ *
+ * Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
+ * on behalf of DENX Software Engineering GmbH
+ *
+ * Based on code from LTIB:
+ * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * 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/list.h>
+
+#include <common.h>
+#include <malloc.h>
+#include <errno.h>
+#include <asm/mmu.h>
+#include <asm/io.h>
+#include <mach/clock.h>
+#include <mach/imx-regs.h>
+#include <mach/dma.h>
+#include <mach/mxs.h>
+
+#define HW_APBHX_CTRL0				0x000
+#define BM_APBH_CTRL0_APB_BURST8_EN		(1 << 29)
+#define BM_APBH_CTRL0_APB_BURST_EN		(1 << 28)
+#define BP_APBH_CTRL0_CLKGATE_CHANNEL		8
+#define BP_APBH_CTRL0_RESET_CHANNEL		16
+#define HW_APBHX_CTRL1				0x010
+#define	BP_APBHX_CTRL1_CH_CMDCMPLT_IRQ_EN	16
+#define HW_APBHX_CTRL2				0x020
+#define HW_APBHX_CHANNEL_CTRL			0x030
+#define BP_APBHX_CHANNEL_CTRL_RESET_CHANNEL	16
+#define HW_APBH_VERSION				(cpu_is_mx23() ? 0x3f0 : 0x800)
+#define HW_APBX_VERSION				0x800
+#define BP_APBHX_VERSION_MAJOR			24
+#define HW_APBHX_CHn_NXTCMDAR(n) \
+	((apbh_is_old ? 0x050 : 0x110) + (n) * 0x70)
+#define HW_APBHX_CHn_SEMA(n) \
+	((apbh_is_old ? 0x080 : 0x140) + (n) * 0x70)
+#define	BM_APBHX_CHn_SEMA_PHORE			(0xff << 16)
+#define	BP_APBHX_CHn_SEMA_PHORE			16
+
+static struct mxs_dma_chan mxs_dma_channels[MXS_MAX_DMA_CHANNELS];
+static bool apbh_is_old;
+
+/*
+ * Test is the DMA channel is valid channel
+ */
+int mxs_dma_validate_chan(int channel)
+{
+	struct mxs_dma_chan *pchan;
+
+	if ((channel < 0) || (channel >= MXS_MAX_DMA_CHANNELS))
+		return -EINVAL;
+
+	pchan = mxs_dma_channels + channel;
+	if (!(pchan->flags & MXS_DMA_FLAGS_ALLOCATED))
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
+ * Return the address of the command within a descriptor.
+ */
+static unsigned int mxs_dma_cmd_address(struct mxs_dma_desc *desc)
+{
+	return desc->address + offsetof(struct mxs_dma_desc, cmd);
+}
+
+/*
+ * Read a DMA channel's hardware semaphore.
+ *
+ * As used by the MXS platform's DMA software, the DMA channel's hardware
+ * semaphore reflects the number of DMA commands the hardware will process, but
+ * has not yet finished. This is a volatile value read directly from hardware,
+ * so it must be be viewed as immediately stale.
+ *
+ * If the channel is not marked busy, or has finished processing all its
+ * commands, this value should be zero.
+ *
+ * See mxs_dma_append() for details on how DMA command blocks must be configured
+ * to maintain the expected behavior of the semaphore's value.
+ */
+static int mxs_dma_read_semaphore(int channel)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	uint32_t tmp;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	tmp = readl(apbh_regs + HW_APBHX_CHn_SEMA(channel));
+
+	tmp &= BM_APBHX_CHn_SEMA_PHORE;
+	tmp >>= BP_APBHX_CHn_SEMA_PHORE;
+
+	return tmp;
+}
+
+/*
+ * Enable a DMA channel.
+ *
+ * If the given channel has any DMA descriptors on its active list, this
+ * function causes the DMA hardware to begin processing them.
+ *
+ * This function marks the DMA channel as "busy," whether or not there are any
+ * descriptors to process.
+ */
+static int mxs_dma_enable(int channel)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	unsigned int sem;
+	struct mxs_dma_chan *pchan;
+	struct mxs_dma_desc *pdesc;
+	int channel_bit, ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	pchan = mxs_dma_channels + channel;
+
+	if (pchan->pending_num == 0) {
+		pchan->flags |= MXS_DMA_FLAGS_BUSY;
+		return 0;
+	}
+
+	pdesc = list_first_entry(&pchan->active, struct mxs_dma_desc, node);
+	if (pdesc == NULL)
+		return -EFAULT;
+
+	if (pchan->flags & MXS_DMA_FLAGS_BUSY) {
+		if (!(pdesc->cmd.data & MXS_DMA_DESC_CHAIN))
+			return 0;
+
+		sem = mxs_dma_read_semaphore(channel);
+		if (sem == 0)
+			return 0;
+
+		if (sem == 1) {
+			pdesc = list_entry(pdesc->node.next,
+					   struct mxs_dma_desc, node);
+			writel(mxs_dma_cmd_address(pdesc),
+				apbh_regs + HW_APBHX_CHn_NXTCMDAR(channel));
+		}
+		writel(pchan->pending_num,
+			apbh_regs + HW_APBHX_CHn_SEMA(channel));
+		pchan->active_num += pchan->pending_num;
+		pchan->pending_num = 0;
+	} else {
+		pchan->active_num += pchan->pending_num;
+		pchan->pending_num = 0;
+		writel(mxs_dma_cmd_address(pdesc),
+			apbh_regs + HW_APBHX_CHn_NXTCMDAR(channel));
+		writel(pchan->active_num,
+			apbh_regs + HW_APBHX_CHn_SEMA(channel));
+		channel_bit = channel + (apbh_is_old ? BP_APBH_CTRL0_CLKGATE_CHANNEL : 0);
+		writel(1 << channel_bit, apbh_regs + HW_APBHX_CTRL0 + BIT_CLR);
+	}
+
+	pchan->flags |= MXS_DMA_FLAGS_BUSY;
+	return 0;
+}
+
+/*
+ * Disable a DMA channel.
+ *
+ * This function shuts down a DMA channel and marks it as "not busy." Any
+ * descriptors on the active list are immediately moved to the head of the
+ * "done" list, whether or not they have actually been processed by the
+ * hardware. The "ready" flags of these descriptors are NOT cleared, so they
+ * still appear to be active.
+ *
+ * This function immediately shuts down a DMA channel's hardware, aborting any
+ * I/O that may be in progress, potentially leaving I/O hardware in an undefined
+ * state. It is unwise to call this function if there is ANY chance the hardware
+ * is still processing a command.
+ */
+static int mxs_dma_disable(int channel)
+{
+	struct mxs_dma_chan *pchan;
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	int channel_bit, ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	pchan = mxs_dma_channels + channel;
+
+	if (!(pchan->flags & MXS_DMA_FLAGS_BUSY))
+		return -EINVAL;
+
+	channel_bit = channel + (apbh_is_old ? BP_APBH_CTRL0_CLKGATE_CHANNEL : 0);
+	writel(1 << channel_bit, apbh_regs + HW_APBHX_CTRL0 + BIT_SET);
+
+	pchan->flags &= ~MXS_DMA_FLAGS_BUSY;
+	pchan->active_num = 0;
+	pchan->pending_num = 0;
+	list_splice_init(&pchan->active, &pchan->done);
+
+	return 0;
+}
+
+/*
+ * Resets the DMA channel hardware.
+ */
+static int mxs_dma_reset(int channel)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	if (apbh_is_old)
+		writel(1 << (channel + BP_APBH_CTRL0_RESET_CHANNEL),
+			apbh_regs + HW_APBHX_CTRL0 + BIT_SET);
+	else
+		writel(1 << (channel + BP_APBHX_CHANNEL_CTRL_RESET_CHANNEL),
+			apbh_regs + HW_APBHX_CHANNEL_CTRL + BIT_SET);
+
+	return 0;
+}
+
+/*
+ * Enable or disable DMA interrupt.
+ *
+ * This function enables the given DMA channel to interrupt the CPU.
+ */
+static int mxs_dma_enable_irq(int channel, int enable)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	if (enable)
+		writel(1 << (channel + BP_APBHX_CTRL1_CH_CMDCMPLT_IRQ_EN),
+			apbh_regs + HW_APBHX_CTRL1 + BIT_SET);
+	else
+		writel(1 << (channel + BP_APBHX_CTRL1_CH_CMDCMPLT_IRQ_EN),
+			apbh_regs + HW_APBHX_CTRL1 + BIT_CLR);
+
+	return 0;
+}
+
+/*
+ * Clear DMA interrupt.
+ *
+ * The software that is using the DMA channel must register to receive its
+ * interrupts and, when they arrive, must call this function to clear them.
+ */
+static int mxs_dma_ack_irq(int channel)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	writel(1 << channel, apbh_regs + HW_APBHX_CTRL1 + BIT_CLR);
+	writel(1 << channel, apbh_regs + HW_APBHX_CTRL2 + BIT_CLR);
+
+	return 0;
+}
+
+/*
+ * Request to reserve a DMA channel
+ */
+static int mxs_dma_request(int channel)
+{
+	struct mxs_dma_chan *pchan;
+
+	if ((channel < 0) || (channel >= MXS_MAX_DMA_CHANNELS))
+		return -EINVAL;
+
+	pchan = mxs_dma_channels + channel;
+	if ((pchan->flags & MXS_DMA_FLAGS_VALID) != MXS_DMA_FLAGS_VALID)
+		return -ENODEV;
+
+	if (pchan->flags & MXS_DMA_FLAGS_ALLOCATED)
+		return -EBUSY;
+
+	pchan->flags |= MXS_DMA_FLAGS_ALLOCATED;
+	pchan->active_num = 0;
+	pchan->pending_num = 0;
+
+	INIT_LIST_HEAD(&pchan->active);
+	INIT_LIST_HEAD(&pchan->done);
+
+	return 0;
+}
+
+/*
+ * Release a DMA channel.
+ *
+ * This function releases a DMA channel from its current owner.
+ *
+ * The channel will NOT be released if it's marked "busy" (see
+ * mxs_dma_enable()).
+ */
+static int mxs_dma_release(int channel)
+{
+	struct mxs_dma_chan *pchan;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	pchan = mxs_dma_channels + channel;
+
+	if (pchan->flags & MXS_DMA_FLAGS_BUSY)
+		return -EBUSY;
+
+	pchan->dev = 0;
+	pchan->active_num = 0;
+	pchan->pending_num = 0;
+	pchan->flags &= ~MXS_DMA_FLAGS_ALLOCATED;
+
+	return 0;
+}
+
+/*
+ * Allocate DMA descriptor
+ */
+struct mxs_dma_desc *mxs_dma_desc_alloc(void)
+{
+	struct mxs_dma_desc *pdesc;
+
+	pdesc = dma_alloc_coherent(sizeof(struct mxs_dma_desc));
+
+	if (pdesc == NULL)
+		return NULL;
+
+	memset(pdesc, 0, sizeof(*pdesc));
+	pdesc->address = (dma_addr_t)pdesc;
+
+	return pdesc;
+};
+
+/*
+ * Free DMA descriptor
+ */
+void mxs_dma_desc_free(struct mxs_dma_desc *pdesc)
+{
+	if (pdesc == NULL)
+		return;
+
+	free(pdesc);
+}
+
+/*
+ * Add a DMA descriptor to a channel.
+ *
+ * If the descriptor list for this channel is not empty, this function sets the
+ * CHAIN bit and the NEXTCMD_ADDR fields in the last descriptor's DMA command so
+ * it will chain to the new descriptor's command.
+ *
+ * Then, this function marks the new descriptor as "ready," adds it to the end
+ * of the active descriptor list, and increments the count of pending
+ * descriptors.
+ *
+ * The MXS platform DMA software imposes some rules on DMA commands to maintain
+ * important invariants. These rules are NOT checked, but they must be carefully
+ * applied by software that uses MXS DMA channels.
+ *
+ * Invariant:
+ *     The DMA channel's hardware semaphore must reflect the number of DMA
+ *     commands the hardware will process, but has not yet finished.
+ *
+ * Explanation:
+ *     A DMA channel begins processing commands when its hardware semaphore is
+ *     written with a value greater than zero, and it stops processing commands
+ *     when the semaphore returns to zero.
+ *
+ *     When a channel finishes a DMA command, it will decrement its semaphore if
+ *     the DECREMENT_SEMAPHORE bit is set in that command's flags bits.
+ *
+ *     In principle, it's not necessary for the DECREMENT_SEMAPHORE to be set,
+ *     unless it suits the purposes of the software. For example, one could
+ *     construct a series of five DMA commands, with the DECREMENT_SEMAPHORE
+ *     bit set only in the last one. Then, setting the DMA channel's hardware
+ *     semaphore to one would cause the entire series of five commands to be
+ *     processed. However, this example would violate the invariant given above.
+ *
+ * Rule:
+ *    ALL DMA commands MUST have the DECREMENT_SEMAPHORE bit set so that the DMA
+ *    channel's hardware semaphore will be decremented EVERY time a command is
+ *    processed.
+ */
+int mxs_dma_desc_append(int channel, struct mxs_dma_desc *pdesc)
+{
+	struct mxs_dma_chan *pchan;
+	struct mxs_dma_desc *last;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	pchan = mxs_dma_channels + channel;
+
+	pdesc->cmd.next = mxs_dma_cmd_address(pdesc);
+	pdesc->flags |= MXS_DMA_DESC_FIRST | MXS_DMA_DESC_LAST;
+
+	if (!list_empty(&pchan->active)) {
+		last = list_entry(pchan->active.prev, struct mxs_dma_desc,
+					node);
+
+		pdesc->flags &= ~MXS_DMA_DESC_FIRST;
+		last->flags &= ~MXS_DMA_DESC_LAST;
+
+		last->cmd.next = mxs_dma_cmd_address(pdesc);
+		last->cmd.data |= MXS_DMA_DESC_CHAIN;
+	}
+	pdesc->flags |= MXS_DMA_DESC_READY;
+	if (pdesc->flags & MXS_DMA_DESC_FIRST)
+		pchan->pending_num++;
+	list_add_tail(&pdesc->node, &pchan->active);
+
+	return ret;
+}
+
+/*
+ * Clean up processed DMA descriptors.
+ *
+ * This function removes processed DMA descriptors from the "active" list. Pass
+ * in a non-NULL list head to get the descriptors moved to your list. Pass NULL
+ * to get the descriptors moved to the channel's "done" list. Descriptors on
+ * the "done" list can be retrieved with mxs_dma_get_finished().
+ *
+ * This function marks the DMA channel as "not busy" if no unprocessed
+ * descriptors remain on the "active" list.
+ */
+static int mxs_dma_finish(int channel, struct list_head *head)
+{
+	int sem;
+	struct mxs_dma_chan *pchan;
+	struct list_head *p, *q;
+	struct mxs_dma_desc *pdesc;
+	int ret;
+
+	ret = mxs_dma_validate_chan(channel);
+	if (ret)
+		return ret;
+
+	pchan = mxs_dma_channels + channel;
+
+	sem = mxs_dma_read_semaphore(channel);
+	if (sem < 0)
+		return sem;
+
+	if (sem == pchan->active_num)
+		return 0;
+
+	list_for_each_safe(p, q, &pchan->active) {
+		if ((pchan->active_num) <= sem)
+			break;
+
+		pdesc = list_entry(p, struct mxs_dma_desc, node);
+		pdesc->flags &= ~MXS_DMA_DESC_READY;
+
+		if (head)
+			list_move_tail(p, head);
+		else
+			list_move_tail(p, &pchan->done);
+
+		if (pdesc->flags & MXS_DMA_DESC_LAST)
+			pchan->active_num--;
+	}
+
+	if (sem == 0)
+		pchan->flags &= ~MXS_DMA_FLAGS_BUSY;
+
+	return 0;
+}
+
+/*
+ * Wait for DMA channel to complete
+ */
+static int mxs_dma_wait_complete(uint32_t timeout, unsigned int chan)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	int ret;
+
+	ret = mxs_dma_validate_chan(chan);
+	if (ret)
+		return ret;
+
+	while (--timeout) {
+		if (readl(apbh_regs + HW_APBHX_CTRL1) & (1 << chan))
+			break;
+		udelay(1);
+	}
+
+	if (timeout == 0) {
+		ret = -ETIMEDOUT;
+		mxs_dma_reset(chan);
+	}
+
+	return ret;
+}
+
+/*
+ * Execute the DMA channel
+ */
+int mxs_dma_go(int chan)
+{
+	uint32_t timeout = 10000;
+	int ret;
+
+	LIST_HEAD(tmp_desc_list);
+
+	mxs_dma_enable_irq(chan, 1);
+	mxs_dma_enable(chan);
+
+	/* Wait for DMA to finish. */
+	ret = mxs_dma_wait_complete(timeout, chan);
+
+	/* Clear out the descriptors we just ran. */
+	mxs_dma_finish(chan, &tmp_desc_list);
+
+	/* Shut the DMA channel down. */
+	mxs_dma_ack_irq(chan);
+	mxs_dma_reset(chan);
+	mxs_dma_enable_irq(chan, 0);
+	mxs_dma_disable(chan);
+
+	return ret;
+}
+
+/*
+ * Initialize the DMA hardware
+ */
+int mxs_dma_init(void)
+{
+	void __iomem *apbh_regs = (void *)MXS_APBH_BASE;
+	struct mxs_dma_chan *pchan;
+	int ret, channel;
+	u32 val, reg;
+
+	mxs_reset_block(apbh_regs, 0);
+
+	/* HACK: Get CPUID and determine APBH version */
+	val = readl(0x8001c310) >> 16;
+	if (val == 0x2800)
+		reg = MXS_APBH_BASE + 0x0800;
+	else
+		reg = MXS_APBH_BASE + 0x03f0;
+
+	apbh_is_old = (readl((void *)reg) >> 24) < 3;
+
+	writel(BM_APBH_CTRL0_APB_BURST8_EN,
+		apbh_regs + HW_APBHX_CTRL0 + BIT_SET);
+
+	writel(BM_APBH_CTRL0_APB_BURST_EN,
+		apbh_regs + HW_APBHX_CTRL0 + BIT_SET);
+
+	for (channel = 0; channel < MXS_MAX_DMA_CHANNELS; channel++) {
+		pchan = mxs_dma_channels + channel;
+		pchan->flags = MXS_DMA_FLAGS_VALID;
+
+		ret = mxs_dma_request(channel);
+
+		if (ret) {
+			printf("MXS DMA: Can't acquire DMA channel %i\n",
+				channel);
+
+			goto err;
+		}
+
+		mxs_dma_reset(channel);
+		mxs_dma_ack_irq(channel);
+	}
+
+	return 0;
+
+err:
+	while (--channel >= 0)
+		mxs_dma_release(channel);
+	return ret;
+}