atmel-mci: Driver for Atmel on-chip MMC controllers

This is a driver for the MMC controller on the AP7000 chips from
Atmel. It should in theory work on AT91 systems too with some
tweaking, but since the DMA interface is quite different, it's not
entirely clear if it's worth merging this with the at91_mci driver.

This driver has been around for a while in BSPs and kernel sources
provided by Atmel, but this particular version uses the generic DMA
Engine framework (with the slave extensions) instead of an
avr32-only DMA controller framework.

This driver can also use PIO transfers when no DMA channels are
available, and for transfers where using DMA may be difficult or
impractical for some reason (e.g. the DMA setup overhead is usually
not worth it for very short transfers, and badly aligned buffers or
lengths are difficult to handle.)

Currently, the driver only support PIO transfers. DMA support has been
split out to a separate patch to hopefully make it easier to review.

The driver has been tested using mmc-block and ext3fs on several SD,
SDHC and MMC+ cards. Reads and writes work fine, with read transfer
rates up to 3.5 MiB/s on fast cards with debugging disabled.

The driver has also been tested using the mmc_test module on the same
cards. All tests except 7, 9, 15 and 17 succeed. The first two are
unsupported by all the cards I have, so I don't know if the driver
handles this correctly. The last two fail because the hardware flags a
Data CRC Error instead of a Data Timeout error. I'm not sure how to deal
with that.

Documentation for this controller can be found in many data sheets from
Atmel, including the AT32AP7000 data sheet which can be found here:

http://www.atmel.com/dyn/products/datasheets.asp?family_id=682

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 981 insertions, 0 deletions

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
new file mode 100644
index 000000000000..25d5324ab7e2
--- /dev/null
+++ b/drivers/mmc/host/atmel-mci.c
@@ -0,0 +1,981 @@
+/*
+ * Atmel MultiMedia Card Interface driver
+ *
+ * Copyright (C) 2004-2008 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/blkdev.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/scatterlist.h>
+
+#include <linux/mmc/host.h>
+
+#include <asm/atmel-mci.h>
+#include <asm/io.h>
+#include <asm/unaligned.h>
+
+#include <asm/arch/board.h>
+#include <asm/arch/gpio.h>
+
+#include "atmel-mci-regs.h"
+
+#define ATMCI_DATA_ERROR_FLAGS	(MCI_DCRCE | MCI_DTOE | MCI_OVRE | MCI_UNRE)
+
+enum {
+	EVENT_CMD_COMPLETE = 0,
+	EVENT_DATA_ERROR,
+	EVENT_DATA_COMPLETE,
+	EVENT_STOP_SENT,
+	EVENT_STOP_COMPLETE,
+	EVENT_XFER_COMPLETE,
+};
+
+struct atmel_mci {
+	struct mmc_host		*mmc;
+	void __iomem		*regs;
+
+	struct scatterlist	*sg;
+	unsigned int		pio_offset;
+
+	struct mmc_request	*mrq;
+	struct mmc_command	*cmd;
+	struct mmc_data		*data;
+
+	u32			cmd_status;
+	u32			data_status;
+	u32			stop_status;
+	u32			stop_cmdr;
+
+	u32			mode_reg;
+	u32			sdc_reg;
+
+	struct tasklet_struct	tasklet;
+	unsigned long		pending_events;
+	unsigned long		completed_events;
+
+	int			present;
+	int			detect_pin;
+	int			wp_pin;
+
+	/* For detect pin debouncing */
+	struct timer_list	detect_timer;
+
+	unsigned long		bus_hz;
+	unsigned long		mapbase;
+	struct clk		*mck;
+	struct platform_device	*pdev;
+};
+
+#define atmci_is_completed(host, event)				\
+	test_bit(event, &host->completed_events)
+#define atmci_test_and_clear_pending(host, event)		\
+	test_and_clear_bit(event, &host->pending_events)
+#define atmci_test_and_set_completed(host, event)		\
+	test_and_set_bit(event, &host->completed_events)
+#define atmci_set_completed(host, event)			\
+	set_bit(event, &host->completed_events)
+#define atmci_set_pending(host, event)				\
+	set_bit(event, &host->pending_events)
+#define atmci_clear_pending(host, event)			\
+	clear_bit(event, &host->pending_events)
+
+
+static void atmci_enable(struct atmel_mci *host)
+{
+	clk_enable(host->mck);
+	mci_writel(host, CR, MCI_CR_MCIEN);
+	mci_writel(host, MR, host->mode_reg);
+	mci_writel(host, SDCR, host->sdc_reg);
+}
+
+static void atmci_disable(struct atmel_mci *host)
+{
+	mci_writel(host, CR, MCI_CR_SWRST);
+
+	/* Stall until write is complete, then disable the bus clock */
+	mci_readl(host, SR);
+	clk_disable(host->mck);
+}
+
+static inline unsigned int ns_to_clocks(struct atmel_mci *host,
+					unsigned int ns)
+{
+	return (ns * (host->bus_hz / 1000000) + 999) / 1000;
+}
+
+static void atmci_set_timeout(struct atmel_mci *host,
+			      struct mmc_data *data)
+{
+	static unsigned	dtomul_to_shift[] = {
+		0, 4, 7, 8, 10, 12, 16, 20
+	};
+	unsigned	timeout;
+	unsigned	dtocyc;
+	unsigned	dtomul;
+
+	timeout = ns_to_clocks(host, data->timeout_ns) + data->timeout_clks;
+
+	for (dtomul = 0; dtomul < 8; dtomul++) {
+		unsigned shift = dtomul_to_shift[dtomul];
+		dtocyc = (timeout + (1 << shift) - 1) >> shift;
+		if (dtocyc < 15)
+			break;
+	}
+
+	if (dtomul >= 8) {
+		dtomul = 7;
+		dtocyc = 15;
+	}
+
+	dev_vdbg(&host->mmc->class_dev, "setting timeout to %u cycles\n",
+			dtocyc << dtomul_to_shift[dtomul]);
+	mci_writel(host, DTOR, (MCI_DTOMUL(dtomul) | MCI_DTOCYC(dtocyc)));
+}
+
+/*
+ * Return mask with command flags to be enabled for this command.
+ */
+static u32 atmci_prepare_command(struct mmc_host *mmc,
+				 struct mmc_command *cmd)
+{
+	struct mmc_data	*data;
+	u32		cmdr;
+
+	cmd->error = -EINPROGRESS;
+
+	cmdr = MCI_CMDR_CMDNB(cmd->opcode);
+
+	if (cmd->flags & MMC_RSP_PRESENT) {
+		if (cmd->flags & MMC_RSP_136)
+			cmdr |= MCI_CMDR_RSPTYP_136BIT;
+		else
+			cmdr |= MCI_CMDR_RSPTYP_48BIT;
+	}
+
+	/*
+	 * This should really be MAXLAT_5 for CMD2 and ACMD41, but
+	 * it's too difficult to determine whether this is an ACMD or
+	 * not. Better make it 64.
+	 */
+	cmdr |= MCI_CMDR_MAXLAT_64CYC;
+
+	if (mmc->ios.bus_mode == MMC_BUSMODE_OPENDRAIN)
+		cmdr |= MCI_CMDR_OPDCMD;
+
+	data = cmd->data;
+	if (data) {
+		cmdr |= MCI_CMDR_START_XFER;
+		if (data->flags & MMC_DATA_STREAM)
+			cmdr |= MCI_CMDR_STREAM;
+		else if (data->blocks > 1)
+			cmdr |= MCI_CMDR_MULTI_BLOCK;
+		else
+			cmdr |= MCI_CMDR_BLOCK;
+
+		if (data->flags & MMC_DATA_READ)
+			cmdr |= MCI_CMDR_TRDIR_READ;
+	}
+
+	return cmdr;
+}
+
+static void atmci_start_command(struct atmel_mci *host,
+				struct mmc_command *cmd,
+				u32 cmd_flags)
+{
+	/* Must read host->cmd after testing event flags */
+	smp_rmb();
+	WARN_ON(host->cmd);
+	host->cmd = cmd;
+
+	dev_vdbg(&host->mmc->class_dev,
+			"start command: ARGR=0x%08x CMDR=0x%08x\n",
+			cmd->arg, cmd_flags);
+
+	mci_writel(host, ARGR, cmd->arg);
+	mci_writel(host, CMDR, cmd_flags);
+}
+
+static void send_stop_cmd(struct mmc_host *mmc, struct mmc_data *data)
+{
+	struct atmel_mci *host = mmc_priv(mmc);
+
+	atmci_start_command(host, data->stop, host->stop_cmdr);
+	mci_writel(host, IER, MCI_CMDRDY);
+}
+
+static void atmci_request_end(struct mmc_host *mmc, struct mmc_request *mrq)
+{
+	struct atmel_mci *host = mmc_priv(mmc);
+
+	WARN_ON(host->cmd || host->data);
+	host->mrq = NULL;
+
+	atmci_disable(host);
+
+	mmc_request_done(mmc, mrq);
+}
+
+/*
+ * Returns a mask of interrupt flags to be enabled after the whole
+ * request has been prepared.
+ */
+static u32 atmci_submit_data(struct mmc_host *mmc, struct mmc_data *data)
+{
+	struct atmel_mci	*host = mmc_priv(mmc);
+	u32			iflags;
+
+	data->error = -EINPROGRESS;
+
+	WARN_ON(host->data);
+	host->sg = NULL;
+	host->data = data;
+
+	mci_writel(host, BLKR, MCI_BCNT(data->blocks)
+			| MCI_BLKLEN(data->blksz));
+	dev_vdbg(&mmc->class_dev, "BLKR=0x%08x\n",
+			MCI_BCNT(data->blocks) | MCI_BLKLEN(data->blksz));
+
+	iflags = ATMCI_DATA_ERROR_FLAGS;
+	host->sg = data->sg;
+	host->pio_offset = 0;
+	if (data->flags & MMC_DATA_READ)
+		iflags |= MCI_RXRDY;
+	else
+		iflags |= MCI_TXRDY;
+
+	return iflags;
+}
+
+static void atmci_request(struct mmc_host *mmc, struct mmc_request *mrq)
+{
+	struct atmel_mci	*host = mmc_priv(mmc);
+	struct mmc_data		*data;
+	struct mmc_command	*cmd;
+	u32			iflags;
+	u32			cmdflags = 0;
+
+	iflags = mci_readl(host, IMR);
+	if (iflags)
+		dev_warn(&mmc->class_dev, "WARNING: IMR=0x%08x\n",
+				mci_readl(host, IMR));
+
+	WARN_ON(host->mrq != NULL);
+
+	/*
+	 * We may "know" the card is gone even though there's still an
+	 * electrical connection. If so, we really need to communicate
+	 * this to the MMC core since there won't be any more
+	 * interrupts as the card is completely removed. Otherwise,
+	 * the MMC core might believe the card is still there even
+	 * though the card was just removed very slowly.
+	 */
+	if (!host->present) {
+		mrq->cmd->error = -ENOMEDIUM;
+		mmc_request_done(mmc, mrq);
+		return;
+	}
+
+	host->mrq = mrq;
+	host->pending_events = 0;
+	host->completed_events = 0;
+
+	atmci_enable(host);
+
+	/* We don't support multiple blocks of weird lengths. */
+	data = mrq->data;
+	if (data) {
+		if (data->blocks > 1 && data->blksz & 3)
+			goto fail;
+		atmci_set_timeout(host, data);
+	}
+
+	iflags = MCI_CMDRDY;
+	cmd = mrq->cmd;
+	cmdflags = atmci_prepare_command(mmc, cmd);
+	atmci_start_command(host, cmd, cmdflags);
+
+	if (data)
+		iflags |= atmci_submit_data(mmc, data);
+
+	if (mrq->stop) {
+		host->stop_cmdr = atmci_prepare_command(mmc, mrq->stop);
+		host->stop_cmdr |= MCI_CMDR_STOP_XFER;
+		if (!(data->flags & MMC_DATA_WRITE))
+			host->stop_cmdr |= MCI_CMDR_TRDIR_READ;
+		if (data->flags & MMC_DATA_STREAM)
+			host->stop_cmdr |= MCI_CMDR_STREAM;
+		else
+			host->stop_cmdr |= MCI_CMDR_MULTI_BLOCK;
+	}
+
+	/*
+	 * We could have enabled interrupts earlier, but I suspect
+	 * that would open up a nice can of interesting race
+	 * conditions (e.g. command and data complete, but stop not
+	 * prepared yet.)
+	 */
+	mci_writel(host, IER, iflags);
+
+	return;
+
+fail:
+	atmci_disable(host);
+	host->mrq = NULL;
+	mrq->cmd->error = -EINVAL;
+	mmc_request_done(mmc, mrq);
+}
+
+static void atmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	struct atmel_mci	*host = mmc_priv(mmc);
+
+	if (ios->clock) {
+		u32 clkdiv;
+
+		/* Set clock rate */
+		clkdiv = DIV_ROUND_UP(host->bus_hz, 2 * ios->clock) - 1;
+		if (clkdiv > 255) {
+			dev_warn(&mmc->class_dev,
+				"clock %u too slow; using %lu\n",
+				ios->clock, host->bus_hz / (2 * 256));
+			clkdiv = 255;
+		}
+
+		host->mode_reg = MCI_MR_CLKDIV(clkdiv) | MCI_MR_WRPROOF
+					| MCI_MR_RDPROOF;
+	}
+
+	switch (ios->bus_width) {
+	case MMC_BUS_WIDTH_1:
+		host->sdc_reg = 0;
+		break;
+	case MMC_BUS_WIDTH_4:
+		host->sdc_reg = MCI_SDCBUS_4BIT;
+		break;
+	}
+
+	switch (ios->power_mode) {
+	case MMC_POWER_ON:
+		/* Send init sequence (74 clock cycles) */
+		atmci_enable(host);
+		mci_writel(host, CMDR, MCI_CMDR_SPCMD_INIT);
+		while (!(mci_readl(host, SR) & MCI_CMDRDY))
+			cpu_relax();
+		atmci_disable(host);
+		break;
+	default:
+		/*
+		 * TODO: None of the currently available AVR32-based
+		 * boards allow MMC power to be turned off. Implement
+		 * power control when this can be tested properly.
+		 */
+		break;
+	}
+}
+
+static int atmci_get_ro(struct mmc_host *mmc)
+{
+	int			read_only = 0;
+	struct atmel_mci	*host = mmc_priv(mmc);
+
+	if (host->wp_pin >= 0) {
+		read_only = gpio_get_value(host->wp_pin);
+		dev_dbg(&mmc->class_dev, "card is %s\n",
+				read_only ? "read-only" : "read-write");
+	} else {
+		dev_dbg(&mmc->class_dev,
+			"no pin for checking read-only switch."
+			" Assuming write-enable.\n");
+	}
+
+	return read_only;
+}
+
+static struct mmc_host_ops atmci_ops = {
+	.request	= atmci_request,
+	.set_ios	= atmci_set_ios,
+	.get_ro		= atmci_get_ro,
+};
+
+static void atmci_command_complete(struct atmel_mci *host,
+			struct mmc_command *cmd, u32 status)
+{
+	/* Read the response from the card (up to 16 bytes) */
+	cmd->resp[0] = mci_readl(host, RSPR);
+	cmd->resp[1] = mci_readl(host, RSPR);
+	cmd->resp[2] = mci_readl(host, RSPR);
+	cmd->resp[3] = mci_readl(host, RSPR);
+
+	if (status & MCI_RTOE)
+		cmd->error = -ETIMEDOUT;
+	else if ((cmd->flags & MMC_RSP_CRC) && (status & MCI_RCRCE))
+		cmd->error = -EILSEQ;
+	else if (status & (MCI_RINDE | MCI_RDIRE | MCI_RENDE))
+		cmd->error = -EIO;
+	else
+		cmd->error = 0;
+
+	if (cmd->error) {
+		dev_dbg(&host->mmc->class_dev,
+			"command error: status=0x%08x\n", status);
+
+		if (cmd->data) {
+			host->data = NULL;
+			mci_writel(host, IDR, MCI_NOTBUSY
+					| MCI_TXRDY | MCI_RXRDY
+					| ATMCI_DATA_ERROR_FLAGS);
+		}
+	}
+}
+
+static void atmci_detect_change(unsigned long data)
+{
+	struct atmel_mci *host = (struct atmel_mci *)data;
+	struct mmc_request *mrq = host->mrq;
+	int present;
+
+	/*
+	 * atmci_remove() sets detect_pin to -1 before freeing the
+	 * interrupt. We must not re-enable the interrupt if it has
+	 * been freed.
+	 */
+	smp_rmb();
+	if (host->detect_pin < 0)
+		return;
+
+	enable_irq(gpio_to_irq(host->detect_pin));
+	present = !gpio_get_value(host->detect_pin);
+
+	dev_vdbg(&host->pdev->dev, "detect change: %d (was %d)\n",
+			present, host->present);
+
+	if (present != host->present) {
+		dev_dbg(&host->mmc->class_dev, "card %s\n",
+			present ? "inserted" : "removed");
+		host->present = present;
+
+		/* Reset controller if card is gone */
+		if (!present) {
+			mci_writel(host, CR, MCI_CR_SWRST);
+			mci_writel(host, IDR, ~0UL);
+			mci_writel(host, CR, MCI_CR_MCIEN);
+		}
+
+		/* Clean up queue if present */
+		if (mrq) {
+			/*
+			 * Reset controller to terminate any ongoing
+			 * commands or data transfers.
+			 */
+			mci_writel(host, CR, MCI_CR_SWRST);
+
+			if (!atmci_is_completed(host, EVENT_CMD_COMPLETE))
+				mrq->cmd->error = -ENOMEDIUM;
+
+			if (mrq->data && !atmci_is_completed(host,
+						EVENT_DATA_COMPLETE)) {
+				host->data = NULL;
+				mrq->data->error = -ENOMEDIUM;
+			}
+			if (mrq->stop && !atmci_is_completed(host,
+						EVENT_STOP_COMPLETE))
+				mrq->stop->error = -ENOMEDIUM;
+
+			host->cmd = NULL;
+			atmci_request_end(host->mmc, mrq);
+		}
+
+		mmc_detect_change(host->mmc, 0);
+	}
+}
+
+static void atmci_tasklet_func(unsigned long priv)
+{
+	struct mmc_host		*mmc = (struct mmc_host *)priv;
+	struct atmel_mci	*host = mmc_priv(mmc);
+	struct mmc_request	*mrq = host->mrq;
+	struct mmc_data		*data = host->data;
+
+	dev_vdbg(&mmc->class_dev,
+		"tasklet: pending/completed/mask %lx/%lx/%x\n",
+		host->pending_events, host->completed_events,
+		mci_readl(host, IMR));
+
+	if (atmci_test_and_clear_pending(host, EVENT_CMD_COMPLETE)) {
+		/*
+		 * host->cmd must be set to NULL before the interrupt
+		 * handler sees EVENT_CMD_COMPLETE
+		 */
+		host->cmd = NULL;
+		smp_wmb();
+		atmci_set_completed(host, EVENT_CMD_COMPLETE);
+		atmci_command_complete(host, mrq->cmd, host->cmd_status);
+
+		if (!mrq->cmd->error && mrq->stop
+				&& atmci_is_completed(host, EVENT_XFER_COMPLETE)
+				&& !atmci_test_and_set_completed(host,
+					EVENT_STOP_SENT))
+			send_stop_cmd(host->mmc, mrq->data);
+	}
+	if (atmci_test_and_clear_pending(host, EVENT_STOP_COMPLETE)) {
+		/*
+		 * host->cmd must be set to NULL before the interrupt
+		 * handler sees EVENT_STOP_COMPLETE
+		 */
+		host->cmd = NULL;
+		smp_wmb();
+		atmci_set_completed(host, EVENT_STOP_COMPLETE);
+		atmci_command_complete(host, mrq->stop, host->stop_status);
+	}
+	if (atmci_test_and_clear_pending(host, EVENT_DATA_ERROR)) {
+		u32 status = host->data_status;
+
+		dev_vdbg(&mmc->class_dev, "data error: status=%08x\n", status);
+
+		atmci_set_completed(host, EVENT_DATA_ERROR);
+		atmci_set_completed(host, EVENT_DATA_COMPLETE);
+
+		if (status & MCI_DTOE) {
+			dev_dbg(&mmc->class_dev,
+					"data timeout error\n");
+			data->error = -ETIMEDOUT;
+		} else if (status & MCI_DCRCE) {
+			dev_dbg(&mmc->class_dev, "data CRC error\n");
+			data->error = -EILSEQ;
+		} else {
+			dev_dbg(&mmc->class_dev,
+					"data FIFO error (status=%08x)\n",
+					status);
+			data->error = -EIO;
+		}
+
+		if (host->present && data->stop
+				&& atmci_is_completed(host, EVENT_CMD_COMPLETE)
+				&& !atmci_test_and_set_completed(
+					host, EVENT_STOP_SENT))
+			send_stop_cmd(host->mmc, data);
+
+		host->data = NULL;
+	}
+	if (atmci_test_and_clear_pending(host, EVENT_DATA_COMPLETE)) {
+		atmci_set_completed(host, EVENT_DATA_COMPLETE);
+
+		if (!atmci_is_completed(host, EVENT_DATA_ERROR)) {
+			data->bytes_xfered = data->blocks * data->blksz;
+			data->error = 0;
+		}
+
+		host->data = NULL;
+	}
+
+	if (host->mrq && !host->cmd && !host->data)
+		atmci_request_end(mmc, host->mrq);
+}
+
+static void atmci_read_data_pio(struct atmel_mci *host)
+{
+	struct scatterlist	*sg = host->sg;
+	void			*buf = sg_virt(sg);
+	unsigned int		offset = host->pio_offset;
+	struct mmc_data		*data = host->data;
+	u32			value;
+	u32			status;
+	unsigned int		nbytes = 0;
+
+	do {
+		value = mci_readl(host, RDR);
+		if (likely(offset + 4 <= sg->length)) {
+			put_unaligned(value, (u32 *)(buf + offset));
+
+			offset += 4;
+			nbytes += 4;
+
+			if (offset == sg->length) {
+				host->sg = sg = sg_next(sg);
+				if (!sg)
+					goto done;
+
+				offset = 0;
+				buf = sg_virt(sg);
+			}
+		} else {
+			unsigned int remaining = sg->length - offset;
+			memcpy(buf + offset, &value, remaining);
+			nbytes += remaining;
+
+			flush_dcache_page(sg_page(sg));
+			host->sg = sg = sg_next(sg);
+			if (!sg)
+				goto done;
+
+			offset = 4 - remaining;
+			buf = sg_virt(sg);
+			memcpy(buf, (u8 *)&value + remaining, offset);
+			nbytes += offset;
+		}
+
+		status = mci_readl(host, SR);
+		if (status & ATMCI_DATA_ERROR_FLAGS) {
+			mci_writel(host, IDR, (MCI_NOTBUSY | MCI_RXRDY
+						| ATMCI_DATA_ERROR_FLAGS));
+			host->data_status = status;
+			atmci_set_pending(host, EVENT_DATA_ERROR);
+			tasklet_schedule(&host->tasklet);
+			break;
+		}
+	} while (status & MCI_RXRDY);
+
+	host->pio_offset = offset;
+	data->bytes_xfered += nbytes;
+
+	return;
+
+done:
+	mci_writel(host, IDR, MCI_RXRDY);
+	mci_writel(host, IER, MCI_NOTBUSY);
+	data->bytes_xfered += nbytes;
+	atmci_set_completed(host, EVENT_XFER_COMPLETE);
+	if (data->stop && atmci_is_completed(host, EVENT_CMD_COMPLETE)
+			&& !atmci_test_and_set_completed(host, EVENT_STOP_SENT))
+		send_stop_cmd(host->mmc, data);
+}
+
+static void atmci_write_data_pio(struct atmel_mci *host)
+{
+	struct scatterlist	*sg = host->sg;
+	void			*buf = sg_virt(sg);
+	unsigned int		offset = host->pio_offset;
+	struct mmc_data		*data = host->data;
+	u32			value;
+	u32			status;
+	unsigned int		nbytes = 0;
+
+	do {
+		if (likely(offset + 4 <= sg->length)) {
+			value = get_unaligned((u32 *)(buf + offset));
+			mci_writel(host, TDR, value);
+
+			offset += 4;
+			nbytes += 4;
+			if (offset == sg->length) {
+				host->sg = sg = sg_next(sg);
+				if (!sg)
+					goto done;
+
+				offset = 0;
+				buf = sg_virt(sg);
+			}
+		} else {
+			unsigned int remaining = sg->length - offset;
+
+			value = 0;
+			memcpy(&value, buf + offset, remaining);
+			nbytes += remaining;
+
+			host->sg = sg = sg_next(sg);
+			if (!sg) {
+				mci_writel(host, TDR, value);
+				goto done;
+			}
+
+			offset = 4 - remaining;
+			buf = sg_virt(sg);
+			memcpy((u8 *)&value + remaining, buf, offset);
+			mci_writel(host, TDR, value);
+			nbytes += offset;
+		}
+
+		status = mci_readl(host, SR);
+		if (status & ATMCI_DATA_ERROR_FLAGS) {
+			mci_writel(host, IDR, (MCI_NOTBUSY | MCI_TXRDY
+						| ATMCI_DATA_ERROR_FLAGS));
+			host->data_status = status;
+			atmci_set_pending(host, EVENT_DATA_ERROR);
+			tasklet_schedule(&host->tasklet);
+			break;
+		}
+	} while (status & MCI_TXRDY);
+
+	host->pio_offset = offset;
+	data->bytes_xfered += nbytes;
+
+	return;
+
+done:
+	mci_writel(host, IDR, MCI_TXRDY);
+	mci_writel(host, IER, MCI_NOTBUSY);
+	data->bytes_xfered += nbytes;
+	atmci_set_completed(host, EVENT_XFER_COMPLETE);
+	if (data->stop && atmci_is_completed(host, EVENT_CMD_COMPLETE)
+			&& !atmci_test_and_set_completed(host, EVENT_STOP_SENT))
+		send_stop_cmd(host->mmc, data);
+}
+
+static void atmci_cmd_interrupt(struct mmc_host *mmc, u32 status)
+{
+	struct atmel_mci	*host = mmc_priv(mmc);
+
+	mci_writel(host, IDR, MCI_CMDRDY);
+
+	if (atmci_is_completed(host, EVENT_STOP_SENT)) {
+		host->stop_status = status;
+		atmci_set_pending(host, EVENT_STOP_COMPLETE);
+	} else {
+		host->cmd_status = status;
+		atmci_set_pending(host, EVENT_CMD_COMPLETE);
+	}
+
+	tasklet_schedule(&host->tasklet);
+}
+
+static irqreturn_t atmci_interrupt(int irq, void *dev_id)
+{
+	struct mmc_host		*mmc = dev_id;
+	struct atmel_mci	*host = mmc_priv(mmc);
+	u32			status, mask, pending;
+	unsigned int		pass_count = 0;
+
+	spin_lock(&mmc->lock);
+
+	do {
+		status = mci_readl(host, SR);
+		mask = mci_readl(host, IMR);
+		pending = status & mask;
+		if (!pending)
+			break;
+
+		if (pending & ATMCI_DATA_ERROR_FLAGS) {
+			mci_writel(host, IDR, ATMCI_DATA_ERROR_FLAGS
+					| MCI_RXRDY | MCI_TXRDY);
+			pending &= mci_readl(host, IMR);
+			host->data_status = status;
+			atmci_set_pending(host, EVENT_DATA_ERROR);
+			tasklet_schedule(&host->tasklet);
+		}
+		if (pending & MCI_NOTBUSY) {
+			mci_writel(host, IDR, (MCI_NOTBUSY
+					       | ATMCI_DATA_ERROR_FLAGS));
+			atmci_set_pending(host, EVENT_DATA_COMPLETE);
+			tasklet_schedule(&host->tasklet);
+		}
+		if (pending & MCI_RXRDY)
+			atmci_read_data_pio(host);
+		if (pending & MCI_TXRDY)
+			atmci_write_data_pio(host);
+
+		if (pending & MCI_CMDRDY)
+			atmci_cmd_interrupt(mmc, status);
+	} while (pass_count++ < 5);
+
+	spin_unlock(&mmc->lock);
+
+	return pass_count ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static irqreturn_t atmci_detect_interrupt(int irq, void *dev_id)
+{
+	struct mmc_host		*mmc = dev_id;
+	struct atmel_mci	*host = mmc_priv(mmc);
+
+	/*
+	 * Disable interrupts until the pin has stabilized and check
+	 * the state then. Use mod_timer() since we may be in the
+	 * middle of the timer routine when this interrupt triggers.
+	 */
+	disable_irq_nosync(irq);
+	mod_timer(&host->detect_timer, jiffies + msecs_to_jiffies(20));
+
+	return IRQ_HANDLED;
+}
+
+static int __init atmci_probe(struct platform_device *pdev)
+{
+	struct mci_platform_data	*pdata;
+	struct atmel_mci *host;
+	struct mmc_host *mmc;
+	struct resource *regs;
+	int irq;
+	int ret;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs)
+		return -ENXIO;
+	pdata = pdev->dev.platform_data;
+	if (!pdata)
+		return -ENXIO;
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	mmc = mmc_alloc_host(sizeof(struct atmel_mci), &pdev->dev);
+	if (!mmc)
+		return -ENOMEM;
+
+	host = mmc_priv(mmc);
+	host->pdev = pdev;
+	host->mmc = mmc;
+	host->detect_pin = pdata->detect_pin;
+	host->wp_pin = pdata->wp_pin;
+
+	host->mck = clk_get(&pdev->dev, "mci_clk");
+	if (IS_ERR(host->mck)) {
+		ret = PTR_ERR(host->mck);
+		goto err_clk_get;
+	}
+
+	ret = -ENOMEM;
+	host->regs = ioremap(regs->start, regs->end - regs->start + 1);
+	if (!host->regs)
+		goto err_ioremap;
+
+	clk_enable(host->mck);
+	mci_writel(host, CR, MCI_CR_SWRST);
+	host->bus_hz = clk_get_rate(host->mck);
+	clk_disable(host->mck);
+
+	host->mapbase = regs->start;
+
+	mmc->ops = &atmci_ops;
+	mmc->f_min = (host->bus_hz + 511) / 512;
+	mmc->f_max = host->bus_hz / 2;
+	mmc->ocr_avail	= MMC_VDD_32_33 | MMC_VDD_33_34;
+	mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_MULTIWRITE;
+
+	mmc->max_hw_segs = 64;
+	mmc->max_phys_segs = 64;
+	mmc->max_req_size = 32768 * 512;
+	mmc->max_blk_size = 32768;
+	mmc->max_blk_count = 512;
+
+	tasklet_init(&host->tasklet, atmci_tasklet_func, (unsigned long)mmc);
+
+	ret = request_irq(irq, atmci_interrupt, 0, pdev->dev.bus_id, mmc);
+	if (ret)
+		goto err_request_irq;
+
+	/* Assume card is present if we don't have a detect pin */
+	host->present = 1;
+	if (host->detect_pin >= 0) {
+		if (gpio_request(host->detect_pin, "mmc_detect")) {
+			dev_dbg(&mmc->class_dev, "no detect pin available\n");
+			host->detect_pin = -1;
+		} else {
+			host->present = !gpio_get_value(host->detect_pin);
+		}
+	}
+	if (host->wp_pin >= 0) {
+		if (gpio_request(host->wp_pin, "mmc_wp")) {
+			dev_dbg(&mmc->class_dev, "no WP pin available\n");
+			host->wp_pin = -1;
+		}
+	}
+
+	platform_set_drvdata(pdev, host);
+
+	mmc_add_host(mmc);
+
+	if (host->detect_pin >= 0) {
+		setup_timer(&host->detect_timer, atmci_detect_change,
+				(unsigned long)host);
+
+		ret = request_irq(gpio_to_irq(host->detect_pin),
+				atmci_detect_interrupt,
+				IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING,
+				"mmc-detect", mmc);
+		if (ret) {
+			dev_dbg(&mmc->class_dev,
+				"could not request IRQ %d for detect pin\n",
+				gpio_to_irq(host->detect_pin));
+			gpio_free(host->detect_pin);
+			host->detect_pin = -1;
+		}
+	}
+
+	dev_info(&mmc->class_dev,
+			"Atmel MCI controller at 0x%08lx irq %d\n",
+			host->mapbase, irq);
+
+	return 0;
+
+err_request_irq:
+	iounmap(host->regs);
+err_ioremap:
+	clk_put(host->mck);
+err_clk_get:
+	mmc_free_host(mmc);
+	return ret;
+}
+
+static int __exit atmci_remove(struct platform_device *pdev)
+{
+	struct atmel_mci *host = platform_get_drvdata(pdev);
+
+	platform_set_drvdata(pdev, NULL);
+
+	if (host) {
+		if (host->detect_pin >= 0) {
+			int pin = host->detect_pin;
+
+			/* Make sure the timer doesn't enable the interrupt */
+			host->detect_pin = -1;
+			smp_wmb();
+
+			free_irq(gpio_to_irq(pin), host->mmc);
+			del_timer_sync(&host->detect_timer);
+			gpio_free(pin);
+		}
+
+		mmc_remove_host(host->mmc);
+
+		clk_enable(host->mck);
+		mci_writel(host, IDR, ~0UL);
+		mci_writel(host, CR, MCI_CR_MCIDIS);
+		mci_readl(host, SR);
+		clk_disable(host->mck);
+
+		if (host->wp_pin >= 0)
+			gpio_free(host->wp_pin);
+
+		free_irq(platform_get_irq(pdev, 0), host->mmc);
+		iounmap(host->regs);
+
+		clk_put(host->mck);
+
+		mmc_free_host(host->mmc);
+	}
+	return 0;
+}
+
+static struct platform_driver atmci_driver = {
+	.remove		= __exit_p(atmci_remove),
+	.driver		= {
+		.name		= "atmel_mci",
+	},
+};
+
+static int __init atmci_init(void)
+{
+	return platform_driver_probe(&atmci_driver, atmci_probe);
+}
+
+static void __exit atmci_exit(void)
+{
+	platform_driver_unregister(&atmci_driver);
+}
+
+module_init(atmci_init);
+module_exit(atmci_exit);
+
+MODULE_DESCRIPTION("Atmel Multimedia Card Interface driver");
+MODULE_AUTHOR("Haavard Skinnemoen <haavard.skinnemoen@atmel.com>");
+MODULE_LICENSE("GPL v2");