Message-Id: <1285628277-26894-4-git-send-email-iws@ovro.caltech.edu>
Date:	Mon, 27 Sep 2010 15:57:56 -0700
From:	"Ira W. Snyder" <iws@...o.caltech.edu>
To:	linux-kernel@...r.kernel.org
Cc:	Dan Williams <dan.j.williams@...el.com>,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 3/4] fsldma: remove DMA_SLAVE support

Now that the generic DMAEngine API has support for scatterlist to
scatterlist copying, this implementation of the DMA_SLAVE API is no
longer necessary.

In order to let device_control() continue to function, a stub
device_prep_slave_sg() function is provided. This allows custom device
configuration, such as enabling external control.

Signed-off-by: Ira W. Snyder <iws@...o.caltech.edu>
---
 arch/powerpc/include/asm/fsldma.h |  115 ++------------------
 drivers/dma/fsldma.c              |  219 +++++++------------------------------
 2 files changed, 48 insertions(+), 286 deletions(-)

diff --git a/arch/powerpc/include/asm/fsldma.h b/arch/powerpc/include/asm/fsldma.h
index debc5ed..dc0bd27 100644
--- a/arch/powerpc/include/asm/fsldma.h
+++ b/arch/powerpc/include/asm/fsldma.h
@@ -1,7 +1,7 @@
 /*
  * Freescale MPC83XX / MPC85XX DMA Controller
  *
- * Copyright (c) 2009 Ira W. Snyder <iws@...o.caltech.edu>
+ * Copyright (c) 2009-2010 Ira W. Snyder <iws@...o.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
@@ -11,127 +11,32 @@
 #ifndef __ARCH_POWERPC_ASM_FSLDMA_H__
 #define __ARCH_POWERPC_ASM_FSLDMA_H__
 
-#include <linux/slab.h>
 #include <linux/dmaengine.h>
 
 /*
- * Definitions for the Freescale DMA controller's DMA_SLAVE implemention
+ * The Freescale DMA controller has several features that are not accomodated
+ * in the Linux DMAEngine API. Therefore, the generic structure is expanded
+ * to allow drivers to use these features.
  *
- * 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.
+ * This structure should be passed into the DMAEngine routine device_control()
+ * as in this example:
  *
- * 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.
+ * chan->device->device_control(chan, DMA_SLAVE_CONFIG, (unsigned long)cfg);
  */
 
 /**
- * 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
+ * @config: the standard Linux DMAEngine API DMA_SLAVE configuration
  * @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 {
+struct fsldma_slave_config {
+	struct dma_slave_config config;
 
-	/* 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 1ed29d1..d3ce25b 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c
@@ -719,207 +719,64 @@ static struct dma_async_tx_descriptor *fsl_dma_prep_slave_sg(
 	struct dma_chan *dchan, struct scatterlist *sgl, unsigned int sg_len,
 	enum dma_data_direction direction, unsigned long flags)
 {
-	struct fsldma_chan *chan;
-	struct fsl_desc_sw *first = NULL, *prev = NULL, *new = NULL;
-	struct fsl_dma_slave *slave;
-	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 (!dchan)
-		return NULL;
-
-	if (!dchan->private)
-		return NULL;
-
-	chan = to_fsl_chan(dchan);
-	slave = dchan->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
+	 * This operation is not supported on the Freescale DMA controller
 	 *
-	 * 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
+	 * However, we need to provide the function pointer to allow the
+	 * device_control() method to work.
 	 */
-	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(chan);
-			if (!new) {
-				dev_err(chan->dev, "No free memory for "
-						       "link descriptor\n");
-				goto fail;
-			}
-#ifdef FSL_DMA_LD_DEBUG
-			dev_dbg(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(chan, &new->hw, copy);
-			set_desc_src(chan, &new->hw, dma_src);
-			set_desc_dst(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(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(chan, new);
-
-	/* Enable extra controller features */
-	if (chan->set_src_loop_size)
-		chan->set_src_loop_size(chan, slave->src_loop_size);
-
-	if (chan->set_dst_loop_size)
-		chan->set_dst_loop_size(chan, slave->dst_loop_size);
-
-	if (chan->toggle_ext_start)
-		chan->toggle_ext_start(chan, slave->external_start);
-
-	if (chan->toggle_ext_pause)
-		chan->toggle_ext_pause(chan, slave->external_pause);
-
-	if (chan->set_request_count)
-		chan->set_request_count(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
-	 */
-	fsldma_free_desc_list_reverse(chan, &first->tx_list);
 	return NULL;
 }
 
 static int fsl_dma_device_control(struct dma_chan *dchan,
 				  enum dma_ctrl_cmd cmd, unsigned long arg)
 {
+	struct fsldma_slave_config *cfg;
 	struct fsldma_chan *chan;
 	unsigned long flags;
 
-	/* Only supports DMA_TERMINATE_ALL */
-	if (cmd != DMA_TERMINATE_ALL)
-		return -ENXIO;
-
 	if (!dchan)
 		return -EINVAL;
 
 	chan = to_fsl_chan(dchan);
 
-	/* Halt the DMA engine */
-	dma_halt(chan);
+	switch (cmd) {
+	case DMA_TERMINATE_ALL:
+		/* Halt the DMA engine */
+		dma_halt(chan);
 
-	spin_lock_irqsave(&chan->desc_lock, flags);
+		spin_lock_irqsave(&chan->desc_lock, flags);
 
-	/* Remove and free all of the descriptors in the LD queue */
-	fsldma_free_desc_list(chan, &chan->ld_pending);
-	fsldma_free_desc_list(chan, &chan->ld_running);
+		/* Remove and free all of the descriptors in the LD queue */
+		fsldma_free_desc_list(chan, &chan->ld_pending);
+		fsldma_free_desc_list(chan, &chan->ld_running);
 
-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+		spin_unlock_irqrestore(&chan->desc_lock, flags);
+		return 0;
+
+	case DMA_SLAVE_CONFIG:
+
+		cfg = (struct fsldma_slave_config *)arg;
+		if (chan->set_request_count)
+			chan->set_request_count(chan, cfg->request_count);
+
+		if (chan->toggle_ext_start)
+			chan->toggle_ext_start(chan, cfg->external_start);
+
+		if (chan->toggle_ext_pause)
+			chan->toggle_ext_pause(chan, cfg->external_pause);
+
+		/*
+		 * TODO: add other features
+		 *
+		 * I'm not sure how to use the members dma_slave_config to
+		 * control the src/dst address hold features.
+		 */
+		return 0;
+
+	default:
+		return -ENXIO;
+	}
 
 	return 0;
 }
-- 
1.7.1

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