fsldma: Add DMA_SLAVE support

Use the DMA_SLAVE capability of the DMAEngine API to copy/from a
scatterlist into an arbitrary list of hardware address/length pairs.

This allows a single DMA transaction to copy data from several different
devices into a scatterlist at the same time.

This also adds support to enable some controller-specific features such as
external start and external pause for a DMA transaction.

[dan.j.williams@intel.com: rebased on tx_list movement]
Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Acked-by: Li Yang <leoli@freescale.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 363 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/fsldma.h b/arch/powerpc/include/asm/fsldma.h
new file mode 100644
index 000000000000..a67aeed17d40
--- /dev/null
+++ b/arch/powerpc/include/asm/fsldma.h
@@ -0,0 +1,136 @@
+/*
+ * Freescale MPC83XX / MPC85XX DMA Controller
+ *
+ * Copyright (c) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#ifndef __ARCH_POWERPC_ASM_FSLDMA_H__
+#define __ARCH_POWERPC_ASM_FSLDMA_H__
+
+#include <linux/dmaengine.h>
+
+/*
+ * Definitions for the Freescale DMA controller's DMA_SLAVE implemention
+ *
+ * The Freescale DMA_SLAVE implementation was designed to handle many-to-many
+ * transfers. An example usage would be an accelerated copy between two
+ * scatterlists. Another example use would be an accelerated copy from
+ * multiple non-contiguous device buffers into a single scatterlist.
+ *
+ * A DMA_SLAVE transaction is defined by a struct fsl_dma_slave. This
+ * structure contains a list of hardware addresses that should be copied
+ * to/from the scatterlist passed into device_prep_slave_sg(). The structure
+ * also has some fields to enable hardware-specific features.
+ */
+
+/**
+ * struct fsl_dma_hw_addr
+ * @entry: linked list entry
+ * @address: the hardware address
+ * @length: length to transfer
+ *
+ * Holds a single physical hardware address / length pair for use
+ * with the DMAEngine DMA_SLAVE API.
+ */
+struct fsl_dma_hw_addr {
+        struct list_head entry;
+
+        dma_addr_t address;
+        size_t length;
+};
+
+/**
+ * struct fsl_dma_slave
+ * @addresses: a linked list of struct fsl_dma_hw_addr structures
+ * @request_count: value for DMA request count
+ * @src_loop_size: setup and enable constant source-address DMA transfers
+ * @dst_loop_size: setup and enable constant destination address DMA transfers
+ * @external_start: enable externally started DMA transfers
+ * @external_pause: enable externally paused DMA transfers
+ *
+ * Holds a list of address / length pairs for use with the DMAEngine
+ * DMA_SLAVE API implementation for the Freescale DMA controller.
+ */
+struct fsl_dma_slave {
+
+        /* List of hardware address/length pairs */
+        struct list_head addresses;
+
+        /* Support for extra controller features */
+        unsigned int request_count;
+        unsigned int src_loop_size;
+        unsigned int dst_loop_size;
+        bool external_start;
+        bool external_pause;
+};
+
+/**
+ * fsl_dma_slave_append - add an address/length pair to a struct fsl_dma_slave
+ * @slave: the &struct fsl_dma_slave to add to
+ * @address: the hardware address to add
+ * @length: the length of bytes to transfer from @address
+ *
+ * Add a hardware address/length pair to a struct fsl_dma_slave. Returns 0 on
+ * success, -ERRNO otherwise.
+ */
+static inline int fsl_dma_slave_append(struct fsl_dma_slave *slave,
+                                       dma_addr_t address, size_t length)
+{
+        struct fsl_dma_hw_addr *addr;
+
+        addr = kzalloc(sizeof(*addr), GFP_ATOMIC);
+        if (!addr)
+                return -ENOMEM;
+
+        INIT_LIST_HEAD(&addr->entry);
+        addr->address = address;
+        addr->length = length;
+
+        list_add_tail(&addr->entry, &slave->addresses);
+        return 0;
+}
+
+/**
+ * fsl_dma_slave_free - free a struct fsl_dma_slave
+ * @slave: the struct fsl_dma_slave to free
+ *
+ * Free a struct fsl_dma_slave and all associated address/length pairs
+ */
+static inline void fsl_dma_slave_free(struct fsl_dma_slave *slave)
+{
+        struct fsl_dma_hw_addr *addr, *tmp;
+
+        if (slave) {
+                list_for_each_entry_safe(addr, tmp, &slave->addresses, entry) {
+                        list_del(&addr->entry);
+                        kfree(addr);
+                }
+
+                kfree(slave);
+        }
+}
+
+/**
+ * fsl_dma_slave_alloc - allocate a struct fsl_dma_slave
+ * @gfp: the flags to pass to kmalloc when allocating this structure
+ *
+ * Allocate a struct fsl_dma_slave for use by the DMA_SLAVE API. Returns a new
+ * struct fsl_dma_slave on success, or NULL on failure.
+ */
+static inline struct fsl_dma_slave *fsl_dma_slave_alloc(gfp_t gfp)
+{
+        struct fsl_dma_slave *slave;
+
+        slave = kzalloc(sizeof(*slave), gfp);
+        if (!slave)
+                return NULL;
+
+        INIT_LIST_HEAD(&slave->addresses);
+        return slave;
+}
+
+#endif /* __ARCH_POWERPC_ASM_FSLDMA_H__ */
diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
index 7a0cb6064f83..296f9e747fac 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c
@@ -34,6 +34,7 @@
 #include <linux/dmapool.h>
 #include <linux/of_platform.h>
 
+#include <asm/fsldma.h>
 #include "fsldma.h"
 
 static void dma_init(struct fsl_dma_chan *fsl_chan)
@@ -552,6 +553,229 @@ fail:
 }
 
 /**
+ * fsl_dma_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
+ * @chan: DMA channel
+ * @sgl: scatterlist to transfer to/from
+ * @sg_len: number of entries in @scatterlist
+ * @direction: DMA direction
+ * @flags: DMAEngine flags
+ *
+ * Prepare a set of descriptors for a DMA_SLAVE transaction. Following the
+ * DMA_SLAVE API, this gets the device-specific information from the
+ * chan->private variable.
+ */
+static struct dma_async_tx_descriptor *fsl_dma_prep_slave_sg(
+        struct dma_chan *chan, struct scatterlist *sgl, unsigned int sg_len,
+        enum dma_data_direction direction, unsigned long flags)
+{
+        struct fsl_dma_chan *fsl_chan;
+        struct fsl_desc_sw *first = NULL, *prev = NULL, *new = NULL;
+        struct fsl_dma_slave *slave;
+        struct list_head *tx_list;
+        size_t copy;
+
+        int i;
+        struct scatterlist *sg;
+        size_t sg_used;
+        size_t hw_used;
+        struct fsl_dma_hw_addr *hw;
+        dma_addr_t dma_dst, dma_src;
+
+        if (!chan)
+                return NULL;
+
+        if (!chan->private)
+                return NULL;
+
+        fsl_chan = to_fsl_chan(chan);
+        slave = chan->private;
+
+        if (list_empty(&slave->addresses))
+                return NULL;
+
+        hw = list_first_entry(&slave->addresses, struct fsl_dma_hw_addr, entry);
+        hw_used = 0;
+
+        /*
+         * Build the hardware transaction to copy from the scatterlist to
+         * the hardware, or from the hardware to the scatterlist
+         *
+         * If you are copying from the hardware to the scatterlist and it
+         * takes two hardware entries to fill an entire page, then both
+         * hardware entries will be coalesced into the same page
+         *
+         * If you are copying from the scatterlist to the hardware and a
+         * single page can fill two hardware entries, then the data will
+         * be read out of the page into the first hardware entry, and so on
+         */
+        for_each_sg(sgl, sg, sg_len, i) {
+                sg_used = 0;
+
+                /* Loop until the entire scatterlist entry is used */
+                while (sg_used < sg_dma_len(sg)) {
+
+                        /*
+                         * If we've used up the current hardware address/length
+                         * pair, we need to load a new one
+                         *
+                         * This is done in a while loop so that descriptors with
+                         * length == 0 will be skipped
+                         */
+                        while (hw_used >= hw->length) {
+
+                                /*
+                                 * If the current hardware entry is the last
+                                 * entry in the list, we're finished
+                                 */
+                                if (list_is_last(&hw->entry, &slave->addresses))
+                                        goto finished;
+
+                                /* Get the next hardware address/length pair */
+                                hw = list_entry(hw->entry.next,
+                                                struct fsl_dma_hw_addr, entry);
+                                hw_used = 0;
+                        }
+
+                        /* Allocate the link descriptor from DMA pool */
+                        new = fsl_dma_alloc_descriptor(fsl_chan);
+                        if (!new) {
+                                dev_err(fsl_chan->dev, "No free memory for "
+                                                       "link descriptor\n");
+                                goto fail;
+                        }
+#ifdef FSL_DMA_LD_DEBUG
+                        dev_dbg(fsl_chan->dev, "new link desc alloc %p\n", new);
+#endif
+
+                        /*
+                         * Calculate the maximum number of bytes to transfer,
+                         * making sure it is less than the DMA controller limit
+                         */
+                        copy = min_t(size_t, sg_dma_len(sg) - sg_used,
+                                             hw->length - hw_used);
+                        copy = min_t(size_t, copy, FSL_DMA_BCR_MAX_CNT);
+
+                        /*
+                         * DMA_FROM_DEVICE
+                         * from the hardware to the scatterlist
+                         *
+                         * DMA_TO_DEVICE
+                         * from the scatterlist to the hardware
+                         */
+                        if (direction == DMA_FROM_DEVICE) {
+                                dma_src = hw->address + hw_used;
+                                dma_dst = sg_dma_address(sg) + sg_used;
+                        } else {
+                                dma_src = sg_dma_address(sg) + sg_used;
+                                dma_dst = hw->address + hw_used;
+                        }
+
+                        /* Fill in the descriptor */
+                        set_desc_cnt(fsl_chan, &new->hw, copy);
+                        set_desc_src(fsl_chan, &new->hw, dma_src);
+                        set_desc_dest(fsl_chan, &new->hw, dma_dst);
+
+                        /*
+                         * If this is not the first descriptor, chain the
+                         * current descriptor after the previous descriptor
+                         */
+                        if (!first) {
+                                first = new;
+                        } else {
+                                set_desc_next(fsl_chan, &prev->hw,
+                                              new->async_tx.phys);
+                        }
+
+                        new->async_tx.cookie = 0;
+                        async_tx_ack(&new->async_tx);
+
+                        prev = new;
+                        sg_used += copy;
+                        hw_used += copy;
+
+                        /* Insert the link descriptor into the LD ring */
+                        list_add_tail(&new->node, &first->tx_list);
+                }
+        }
+
+finished:
+
+        /* All of the hardware address/length pairs had length == 0 */
+        if (!first || !new)
+                return NULL;
+
+        new->async_tx.flags = flags;
+        new->async_tx.cookie = -EBUSY;
+
+        /* Set End-of-link to the last link descriptor of new list */
+        set_ld_eol(fsl_chan, new);
+
+        /* Enable extra controller features */
+        if (fsl_chan->set_src_loop_size)
+                fsl_chan->set_src_loop_size(fsl_chan, slave->src_loop_size);
+
+        if (fsl_chan->set_dest_loop_size)
+                fsl_chan->set_dest_loop_size(fsl_chan, slave->dst_loop_size);
+
+        if (fsl_chan->toggle_ext_start)
+                fsl_chan->toggle_ext_start(fsl_chan, slave->external_start);
+
+        if (fsl_chan->toggle_ext_pause)
+                fsl_chan->toggle_ext_pause(fsl_chan, slave->external_pause);
+
+        if (fsl_chan->set_request_count)
+                fsl_chan->set_request_count(fsl_chan, slave->request_count);
+
+        return &first->async_tx;
+
+fail:
+        /* If first was not set, then we failed to allocate the very first
+         * descriptor, and we're done */
+        if (!first)
+                return NULL;
+
+        /*
+         * First is set, so all of the descriptors we allocated have been added
+         * to first->tx_list, INCLUDING "first" itself. Therefore we
+         * must traverse the list backwards freeing each descriptor in turn
+         *
+         * We're re-using variables for the loop, oh well
+         */
+        tx_list = &first->tx_list;
+        list_for_each_entry_safe_reverse(new, prev, tx_list, node) {
+                list_del_init(&new->node);
+                dma_pool_free(fsl_chan->desc_pool, new, new->async_tx.phys);
+        }
+
+        return NULL;
+}
+
+static void fsl_dma_device_terminate_all(struct dma_chan *chan)
+{
+        struct fsl_dma_chan *fsl_chan;
+        struct fsl_desc_sw *desc, *tmp;
+        unsigned long flags;
+
+        if (!chan)
+                return;
+
+        fsl_chan = to_fsl_chan(chan);
+
+        /* Halt the DMA engine */
+        dma_halt(fsl_chan);
+
+        spin_lock_irqsave(&fsl_chan->desc_lock, flags);
+
+        /* Remove and free all of the descriptors in the LD queue */
+        list_for_each_entry_safe(desc, tmp, &fsl_chan->ld_queue, node) {
+                list_del(&desc->node);
+                dma_pool_free(fsl_chan->desc_pool, desc, desc->async_tx.phys);
+        }
+
+        spin_unlock_irqrestore(&fsl_chan->desc_lock, flags);
+}
+
+/**
  * fsl_dma_update_completed_cookie - Update the completed cookie.
  * @fsl_chan : Freescale DMA channel
  */
@@ -977,12 +1201,15 @@ static int __devinit of_fsl_dma_probe(struct of_device *dev,
 
         dma_cap_set(DMA_MEMCPY, fdev->common.cap_mask);
         dma_cap_set(DMA_INTERRUPT, fdev->common.cap_mask);
+        dma_cap_set(DMA_SLAVE, fdev->common.cap_mask);
         fdev->common.device_alloc_chan_resources = fsl_dma_alloc_chan_resources;
         fdev->common.device_free_chan_resources = fsl_dma_free_chan_resources;
         fdev->common.device_prep_dma_interrupt = fsl_dma_prep_interrupt;
         fdev->common.device_prep_dma_memcpy = fsl_dma_prep_memcpy;
         fdev->common.device_is_tx_complete = fsl_dma_is_complete;
         fdev->common.device_issue_pending = fsl_dma_memcpy_issue_pending;
+        fdev->common.device_prep_slave_sg = fsl_dma_prep_slave_sg;
+        fdev->common.device_terminate_all = fsl_dma_device_terminate_all;
         fdev->common.dev = &dev->dev;
 
         fdev->irq = irq_of_parse_and_map(dev->node, 0);