Message-Id: <1222101497-21183-5-git-send-email-haavard.skinnemoen@atmel.com>
Date:	Mon, 22 Sep 2008 18:38:17 +0200
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Pierre Ossman <drzeus-list@...eus.cx>
Cc:	kernel@...32linux.org, linux-kernel@...r.kernel.org,
	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Subject: [PATCH 4/4] atmel-mci: Add experimental DMA support

This adds support for DMA transfers through the generic DMA engine
framework with the DMA slave extensions.

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 7.5 MiB/s on fast cards with debugging disabled.

Unfortunately, the driver has been known to lock up from time to time
with DMA enabled, so DMA support is currently optional and marked
EXPERIMENTAL. I didn't see any problems while testing it prior to
submission, but I'm still not 100% convinced this bug is gone.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
---
 arch/avr32/include/asm/atmel-mci.h  |    3 +
 arch/avr32/mach-at32ap/at32ap700x.c |   16 +++
 drivers/mmc/host/Kconfig            |   11 ++
 drivers/mmc/host/atmel-mci.c        |  246 ++++++++++++++++++++++++++++++++++-
 4 files changed, 270 insertions(+), 6 deletions(-)

diff --git a/arch/avr32/include/asm/atmel-mci.h b/arch/avr32/include/asm/atmel-mci.h
index 27371c2..37f978c 100644
--- a/arch/avr32/include/asm/atmel-mci.h
+++ b/arch/avr32/include/asm/atmel-mci.h
@@ -1,6 +1,8 @@
 #ifndef __ASM_AVR32_ATMEL_MCI_H
 #define __ASM_AVR32_ATMEL_MCI_H
 
+struct dma_slave;
+
 /**
  * struct mci_slot_pdata - board-specific per-slot configuration
  * @bus_width: Number of data lines wired up the slot
@@ -24,6 +26,7 @@ struct mci_slot_pdata {
  * @slot: Per-slot configuration data.
  */
 struct mci_platform_data {
+	struct dma_slave	*dma_slave;
 	struct mci_slot_pdata	slot[2];
 };
 
diff --git a/arch/avr32/mach-at32ap/at32ap700x.c b/arch/avr32/mach-at32ap/at32ap700x.c
index 9967d5a..f1b9a3a 100644
--- a/arch/avr32/mach-at32ap/at32ap700x.c
+++ b/arch/avr32/mach-at32ap/at32ap700x.c
@@ -1273,6 +1273,7 @@ struct platform_device *__init
 at32_add_device_mci(unsigned int id, struct mci_platform_data *data)
 {
 	struct platform_device		*pdev;
+	struct dw_dma_slave		*dws;
 
 	if (id != 0 || !data)
 		return NULL;
@@ -1289,6 +1290,21 @@ at32_add_device_mci(unsigned int id, struct mci_platform_data *data)
 				ARRAY_SIZE(atmel_mci0_resource)))
 		goto fail;
 
+	if (data->dma_slave)
+		dws = kmemdup(to_dw_dma_slave(data->dma_slave),
+				sizeof(struct dw_dma_slave), GFP_KERNEL);
+	else
+		dws = kzalloc(sizeof(struct dw_dma_slave), GFP_KERNEL);
+
+	dws->slave.dev = &pdev->dev;
+	dws->slave.dma_dev = &dw_dmac0_device.dev;
+	dws->slave.reg_width = DMA_SLAVE_WIDTH_32BIT;
+	dws->cfg_hi = (DWC_CFGH_SRC_PER(0)
+				| DWC_CFGH_DST_PER(1));
+	dws->cfg_lo &= ~(DWC_CFGL_HS_DST_POL
+				| DWC_CFGL_HS_SRC_POL);
+
+	data->dma_slave = &dws->slave;
 
 	if (platform_device_add_data(pdev, data,
 				sizeof(struct mci_platform_data)))
diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index ea8d7a3..1ce21d4 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -114,6 +114,17 @@ config MMC_ATMELMCI
 
 	  If unsure, say N.
 
+config MMC_ATMELMCI_DMA
+	bool "Atmel MCI DMA support (EXPERIMENTAL)"
+	depends on MMC_ATMELMCI && DMA_ENGINE && EXPERIMENTAL
+	help
+	  Say Y here to have the Atmel MCI driver use a DMA engine to
+	  do data transfers and thus increase the throughput and
+	  reduce the CPU utilization. Note that this is highly
+	  experimental and may cause the driver to lock up.
+
+	  If unsure, say N.
+
 config MMC_IMX
 	tristate "Motorola i.MX Multimedia Card Interface support"
 	depends on ARCH_IMX
diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index a7de55f..b35ab11 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -11,6 +11,8 @@
 #include <linux/clk.h>
 #include <linux/debugfs.h>
 #include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/gpio.h>
 #include <linux/init.h>
@@ -33,6 +35,7 @@
 #include "atmel-mci-regs.h"
 
 #define ATMCI_DATA_ERROR_FLAGS	(MCI_DCRCE | MCI_DTOE | MCI_OVRE | MCI_UNRE)
+#define ATMCI_DMA_THRESHOLD	16
 
 enum {
 	EVENT_CMD_COMPLETE = 0,
@@ -50,6 +53,14 @@ enum atmel_mci_state {
 	STATE_DATA_ERROR,
 };
 
+struct atmel_mci_dma {
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+	struct dma_client		client;
+	struct dma_chan			*chan;
+	struct dma_async_tx_descriptor	*data_desc;
+#endif
+};
+
 /**
  * struct atmel_mci - MMC controller state shared between all slots
  * @lock: Spinlock protecting the queue and associated data.
@@ -121,6 +132,9 @@ struct atmel_mci {
 	struct mmc_command	*cmd;
 	struct mmc_data		*data;
 
+	struct atmel_mci_dma	dma;
+	struct dma_chan		*data_chan;
+
 	u32			cmd_status;
 	u32			data_status;
 	u32			stop_cmdr;
@@ -481,6 +495,138 @@ static void send_stop_cmd(struct atmel_mci *host, struct mmc_data *data)
 	mci_writel(host, IER, MCI_CMDRDY);
 }
 
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+static void atmci_dma_cleanup(struct atmel_mci *host)
+{
+	struct mmc_data			*data = host->data;
+
+	dma_unmap_sg(&host->pdev->dev, data->sg, data->sg_len,
+		     ((data->flags & MMC_DATA_WRITE)
+		      ? DMA_TO_DEVICE : DMA_FROM_DEVICE));
+}
+
+static void atmci_stop_dma(struct atmel_mci *host)
+{
+	struct dma_chan *chan = host->data_chan;
+
+	if (chan) {
+		chan->device->device_terminate_all(chan);
+		atmci_dma_cleanup(host);
+	}
+}
+
+/* This function is called by the DMA driver from tasklet context. */
+static void atmci_dma_complete(void *arg)
+{
+	struct atmel_mci	*host = arg;
+	struct mmc_data		*data = host->data;
+
+	dev_vdbg(&host->pdev->dev, "DMA complete\n");
+
+	atmci_dma_cleanup(host);
+
+	/*
+	 * If the card was removed, data will be NULL. No point trying
+	 * to send the stop command or waiting for NBUSY in this case.
+	 */
+	if (data) {
+		atmci_set_pending(host, EVENT_XFER_COMPLETE);
+		tasklet_schedule(&host->tasklet);
+
+		/*
+		 * Regardless of what the documentation says, we have
+		 * to wait for NOTBUSY even after block read
+		 * operations.
+		 *
+		 * When the DMA transfer is complete, the controller
+		 * may still be reading the CRC from the card, i.e.
+		 * the data transfer is still in progress and we
+		 * haven't seen all the potential error bits yet.
+		 *
+		 * The interrupt handler will schedule a different
+		 * tasklet to finish things up when the data transfer
+		 * is completely done.
+		 *
+		 * We may not complete the mmc request here anyway
+		 * because the mmc layer may call back and cause us to
+		 * violate the "don't submit new operations from the
+		 * completion callback" rule of the dma engine
+		 * framework.
+		 */
+		mci_writel(host, IER, MCI_NOTBUSY);
+	}
+}
+
+static int
+atmci_submit_data_dma(struct atmel_mci *host, struct mmc_data *data)
+{
+	struct dma_chan			*chan;
+	struct dma_async_tx_descriptor	*desc;
+	struct scatterlist		*sg;
+	unsigned int			i;
+	enum dma_data_direction		direction;
+
+	/*
+	 * We don't do DMA on "complex" transfers, i.e. with
+	 * non-word-aligned buffers or lengths. Also, we don't bother
+	 * with all the DMA setup overhead for short transfers.
+	 */
+	if (data->blocks * data->blksz < ATMCI_DMA_THRESHOLD)
+		return -EINVAL;
+	if (data->blksz & 3)
+		return -EINVAL;
+
+	for_each_sg(data->sg, sg, data->sg_len, i) {
+		if (sg->offset & 3 || sg->length & 3)
+			return -EINVAL;
+	}
+
+	/* If we don't have a channel, we can't do DMA */
+	chan = host->dma.chan;
+	if (chan) {
+		dma_chan_get(chan);
+		host->data_chan = chan;
+	}
+
+	if (!chan)
+		return -ENODEV;
+
+	if (data->flags & MMC_DATA_READ)
+		direction = DMA_FROM_DEVICE;
+	else
+		direction = DMA_TO_DEVICE;
+
+	desc = chan->device->device_prep_slave_sg(chan,
+			data->sg, data->sg_len, direction,
+			DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	if (!desc)
+		return -ENOMEM;
+
+	host->dma.data_desc = desc;
+	desc->callback = atmci_dma_complete;
+	desc->callback_param = host;
+	desc->tx_submit(desc);
+
+	/* Go! */
+	chan->device->device_issue_pending(chan);
+
+	return 0;
+}
+
+#else /* CONFIG_MMC_ATMELMCI_DMA */
+
+static int atmci_submit_data_dma(struct atmel_mci *host, struct mmc_data *data)
+{
+	return -ENOSYS;
+}
+
+static void atmci_stop_dma(struct atmel_mci *host)
+{
+
+}
+
+#endif /* CONFIG_MMC_ATMELMCI_DMA */
+
 /*
  * Returns a mask of interrupt flags to be enabled after the whole
  * request has been prepared.
@@ -496,12 +642,15 @@ static u32 atmci_submit_data(struct atmel_mci *host, struct mmc_data *data)
 	host->data = data;
 
 	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;
+	if (atmci_submit_data_dma(host, data)) {
+		host->data_chan = NULL;
+		host->sg = data->sg;
+		host->pio_offset = 0;
+		if (data->flags & MMC_DATA_READ)
+			iflags |= MCI_RXRDY;
+		else
+			iflags |= MCI_TXRDY;
+	}
 
 	return iflags;
 }
@@ -767,6 +916,7 @@ static void atmci_command_complete(struct atmel_mci *host,
 
 		if (cmd->data) {
 			host->data = NULL;
+			atmci_stop_dma(host);
 			mci_writel(host, IDR, MCI_NOTBUSY
 					| MCI_TXRDY | MCI_RXRDY
 					| ATMCI_DATA_ERROR_FLAGS);
@@ -834,6 +984,7 @@ static void atmci_detect_change(unsigned long data)
 					/* fall through */
 				case STATE_SENDING_DATA:
 					mrq->data->error = -ENOMEDIUM;
+					atmci_stop_dma(host);
 					break;
 				case STATE_DATA_BUSY:
 				case STATE_DATA_ERROR:
@@ -912,6 +1063,7 @@ static void atmci_tasklet_func(unsigned long priv)
 		case STATE_SENDING_DATA:
 			if (atmci_test_and_clear_pending(host,
 						EVENT_DATA_ERROR)) {
+				atmci_stop_dma(host);
 				if (data->stop)
 					send_stop_cmd(host, data);
 				state = STATE_DATA_ERROR;
@@ -1197,6 +1349,60 @@ static irqreturn_t atmci_detect_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+
+static inline struct atmel_mci *
+dma_client_to_atmel_mci(struct dma_client *client)
+{
+	return container_of(client, struct atmel_mci, dma.client);
+}
+
+static enum dma_state_client atmci_dma_event(struct dma_client *client,
+		struct dma_chan *chan, enum dma_state state)
+{
+	struct atmel_mci	*host;
+	enum dma_state_client	ret = DMA_NAK;
+
+	host = dma_client_to_atmel_mci(client);
+
+	switch (state) {
+	case DMA_RESOURCE_AVAILABLE:
+		spin_lock_bh(&host->lock);
+		if (!host->dma.chan) {
+			host->dma.chan = chan;
+			ret = DMA_ACK;
+		}
+		spin_unlock_bh(&host->lock);
+
+		if (ret == DMA_ACK)
+			dev_info(&host->pdev->dev,
+					"Using %s for DMA transfers\n",
+					chan->dev.bus_id);
+		break;
+
+	case DMA_RESOURCE_REMOVED:
+		spin_lock_bh(&host->lock);
+		if (host->dma.chan == chan) {
+			host->dma.chan = NULL;
+			ret = DMA_ACK;
+		}
+		spin_unlock_bh(&host->lock);
+
+		if (ret == DMA_ACK)
+			dev_info(&host->pdev->dev,
+					"Lost %s, falling back to PIO\n",
+					chan->dev.bus_id);
+		break;
+
+	default:
+		break;
+	}
+
+
+	return ret;
+}
+#endif /* CONFIG_MMC_ATMELMCI_DMA */
+
 static int __init atmci_init_slot(struct atmel_mci *host,
 		struct mci_slot_pdata *slot_data, u32 sdc_reg)
 {
@@ -1350,6 +1556,25 @@ static int __init atmci_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_request_irq;
 
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+	if (pdata->dma_slave) {
+		struct dma_slave *slave = pdata->dma_slave;
+
+		slave->tx_reg = regs->start + MCI_TDR;
+		slave->rx_reg = regs->start + MCI_RDR;
+
+		/* Try to grab a DMA channel */
+		host->dma.client.event_callback = atmci_dma_event;
+		dma_cap_set(DMA_SLAVE, host->dma.client.cap_mask);
+		host->dma.client.slave = slave;
+
+		dma_async_client_register(&host->dma.client);
+		dma_async_client_chan_request(&host->dma.client);
+	} else {
+		dev_notice(&pdev->dev, "DMA not available, using PIO\n");
+	}
+#endif /* CONFIG_MMC_ATMELMCI_DMA */
+
 	platform_set_drvdata(pdev, host);
 
 	/* We need at least one slot to succeed */
@@ -1371,6 +1596,10 @@ static int __init atmci_probe(struct platform_device *pdev)
 	return 0;
 
 err_init_slot:
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+	if (pdata->dma_slave)
+		dma_async_client_unregister(&host->dma.client);
+#endif
 	free_irq(irq, host);
 err_request_irq:
 	iounmap(host->regs);
@@ -1397,6 +1626,11 @@ static int __exit atmci_remove(struct platform_device *pdev)
 	mci_readl(host, SR);
 	clk_disable(host->mck);
 
+#ifdef CONFIG_MMC_ATMELMCI_DMA
+	if (host->dma.client.slave)
+		dma_async_client_unregister(&host->dma.client);
+#endif
+
 	free_irq(platform_get_irq(pdev, 0), host);
 	iounmap(host->regs);
 
-- 
1.5.6.5

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