2 files changed, 269 insertions, 16 deletions

diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index ea8d7a3490d9..1ce21d4c8608 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 d8ab35175a53..d45dfa259386 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.
@@ -62,6 +73,8 @@ enum atmel_mci_state {
  * @cmd: The command currently being sent to the card, or NULL.
  * @data: The data currently being transferred, or NULL if no data
  *      transfer is in progress.
+ * @dma: DMA client state.
+ * @data_chan: DMA channel being used for the current data transfer.
  * @cmd_status: Snapshot of SR taken upon completion of the current
  *      command. Only valid when EVENT_CMD_COMPLETE is pending.
  * @data_status: Snapshot of SR taken upon completion of the current
@@ -126,6 +139,9 @@ 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;
@@ -485,6 +501,144 @@ 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);
+        } else {
+                /* Data transfer was stopped by the interrupt handler */
+                atmci_set_pending(host, EVENT_XFER_COMPLETE);
+                mci_writel(host, IER, MCI_NOTBUSY);
+        }
+}
+
+/* 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)
+{
+        /* Data transfer was stopped by the interrupt handler */
+        atmci_set_pending(host, EVENT_XFER_COMPLETE);
+        mci_writel(host, IER, MCI_NOTBUSY);
+}
+
+#endif /* CONFIG_MMC_ATMELMCI_DMA */
+
 /*
  * Returns a mask of interrupt flags to be enabled after the whole
  * request has been prepared.
@@ -500,24 +654,27 @@ static u32 atmci_submit_data(struct atmel_mci *host, struct mmc_data *data)
         host->data = data;
 
         iflags = ATMCI_DATA_ERROR_FLAGS;
+        if (atmci_submit_data_dma(host, data)) {
+                host->data_chan = NULL;
 
-        /*
-         * Errata: MMC data write operation with less than 12
-         * bytes is impossible.
-         *
-         * Errata: MCI Transmit Data Register (TDR) FIFO
-         * corruption when length is not multiple of 4.
-         */
-        if (data->blocks * data->blksz < 12
-                        || (data->blocks * data->blksz) & 3)
-                host->need_reset = true;
+                /*
+                 * Errata: MMC data write operation with less than 12
+                 * bytes is impossible.
+                 *
+                 * Errata: MCI Transmit Data Register (TDR) FIFO
+                 * corruption when length is not multiple of 4.
+                 */
+                if (data->blocks * data->blksz < 12
+                                || (data->blocks * data->blksz) & 3)
+                        host->need_reset = true;
 
-        host->sg = data->sg;
-        host->pio_offset = 0;
-        if (data->flags & MMC_DATA_READ)
-                iflags |= MCI_RXRDY;
-        else
-                iflags |= MCI_TXRDY;
+                host->sg = data->sg;
+                host->pio_offset = 0;
+                if (data->flags & MMC_DATA_READ)
+                        iflags |= MCI_RXRDY;
+                else
+                        iflags |= MCI_TXRDY;
+        }
 
         return iflags;
 }
@@ -848,6 +1005,7 @@ 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);
@@ -917,6 +1075,7 @@ 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:
@@ -995,6 +1154,7 @@ 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;
@@ -1280,6 +1440,60 @@ 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, unsigned int id,
                 u32 sdc_reg)
@@ -1434,6 +1648,25 @@ 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 */
@@ -1462,6 +1695,10 @@ 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);
@@ -1490,6 +1727,11 @@ 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);