[PATCH RFC v4 2/5] dma: mpc512x: add support for peripheral transfers

[Alexander Popov <a13xp0p0v88@gmail.com>]

Introduce support for slave s/g transfer preparation and the associated
device control callback in the MPC512x DMA controller driver, which adds
support for data transfers between memory and peripheral I/O to the
previously supported mem-to-mem transfers.

Refuse to prepare chunked transfers (transfers with more than one part)
as long as proper support for scatter/gather is lacking.

Keep MPC8308 operational by always starting transfers from software,
this SoC appears to not have request lines for flow control when
peripherals are involved in transfers.

Signed-off-by: Alexander Popov <a13xp0p0v88@gmail.com>
---
 drivers/dma/mpc512x_dma.c | 201 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 193 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
index f41639f..d0c8950 100644
--- a/drivers/dma/mpc512x_dma.c
+++ b/drivers/dma/mpc512x_dma.c
@@ -2,6 +2,7 @@
  * Copyright (C) Freescale Semicondutor, Inc. 2007, 2008.
  * Copyright (C) Semihalf 2009
  * Copyright (C) Ilya Yanok, Emcraft Systems 2010
+ * Copyright (C) Alexander Popov, Promcontroller 2013
  *
  * Written by Piotr Ziecik <kosmo@semihalf.com>. Hardware description
  * (defines, structures and comments) was taken from MPC5121 DMA driver
@@ -28,11 +29,6 @@
  * file called COPYING.
  */
 
-/*
- * This is initial version of MPC5121 DMA driver. Only memory to memory
- * transfers are supported (tested using dmatest module).
- */
-
 #include <linux/module.h>
 #include <linux/dmaengine.h>
 #include <linux/dma-mapping.h>
@@ -187,6 +183,7 @@ struct mpc_dma_desc {
 	dma_addr_t			tcd_paddr;
 	int				error;
 	struct list_head		node;
+	int				will_access_peripheral;
 };
 
 struct mpc_dma_chan {
@@ -199,6 +196,10 @@ struct mpc_dma_chan {
 	struct mpc_dma_tcd		*tcd;
 	dma_addr_t			tcd_paddr;
 
+	/* Settings for access to peripheral FIFO */
+	dma_addr_t			per_paddr;	/* FIFO address */
+	u32				tcd_nunits;
+
 	/* Lock for this structure */
 	spinlock_t			lock;
 };
@@ -247,10 +248,27 @@ static void mpc_dma_execute(struct mpc_dma_chan *mchan)
 	struct mpc_dma_desc *first = NULL;
 	struct mpc_dma_desc *prev = NULL;
 	struct mpc_dma_desc *mdesc;
+	int staffed = 0;
 	int cid = mchan->chan.chan_id;
 
-	/* Move all queued descriptors to active list */
-	list_splice_tail_init(&mchan->queued, &mchan->active);
+	/*
+	 * Mem-to-mem transfers can be chained
+	 * together into one transaction.
+	 * But each transfer which involves peripherals
+	 * must be executed separately.
+	 */
+	while (!staffed) {
+		mdesc = list_first_entry(&mchan->queued,
+						struct mpc_dma_desc, node);
+
+		if (!mdesc->will_access_peripheral)
+			list_move_tail(&mdesc->node, &mchan->active);
+		else {
+			staffed = 1;
+			if (list_empty(&mchan->active))
+				list_move_tail(&mdesc->node, &mchan->active);
+		}
+	}
 
 	/* Chain descriptors into one transaction */
 	list_for_each_entry(mdesc, &mchan->active, node) {
@@ -264,6 +282,8 @@ static void mpc_dma_execute(struct mpc_dma_chan *mchan)
 
 		prev->tcd->dlast_sga = mdesc->tcd_paddr;
 		prev->tcd->e_sg = 1;
+
+		/* software start for mem-to-mem transfers */
 		mdesc->tcd->start = 1;
 
 		prev = mdesc;
@@ -276,7 +296,17 @@ static void mpc_dma_execute(struct mpc_dma_chan *mchan)
 
 	if (first != prev)
 		mdma->tcd[cid].e_sg = 1;
-	out_8(&mdma->regs->dmassrt, cid);
+
+	if (mdma->is_mpc8308) {
+		/* MPC8308, no request lines, software initiated start */
+		out_8(&mdma->regs->dmassrt, cid);
+	} else if (first->will_access_peripheral) {
+		/* peripherals involved, use external request line */
+		out_8(&mdma->regs->dmaserq, cid);
+	} else {
+		/* memory to memory transfer, software initiated start */
+		out_8(&mdma->regs->dmassrt, cid);
+	}
 }
 
 /* Handle interrupt on one half of DMA controller (32 channels) */
@@ -594,6 +624,7 @@ mpc_dma_prep_memcpy(struct dma_chan *chan, dma_addr_t dst, dma_addr_t src,
 	}
 
 	mdesc->error = 0;
+	mdesc->will_access_peripheral = 0;
 	tcd = mdesc->tcd;
 
 	/* Prepare Transfer Control Descriptor for this transaction */
@@ -641,6 +672,157 @@ mpc_dma_prep_memcpy(struct dma_chan *chan, dma_addr_t dst, dma_addr_t src,
 	return &mdesc->desc;
 }
 
+static struct dma_async_tx_descriptor *mpc_dma_prep_slave_sg(
+		struct dma_chan *chan, struct scatterlist *sgl,
+		unsigned int sg_len, enum dma_transfer_direction direction,
+		unsigned long flags, void *context)
+{
+	struct mpc_dma *mdma = dma_chan_to_mpc_dma(chan);
+	struct mpc_dma_chan *mchan = dma_chan_to_mpc_dma_chan(chan);
+	struct mpc_dma_desc *mdesc = NULL;
+	dma_addr_t per_paddr;
+	u32 tcd_nunits = 0;
+	struct mpc_dma_tcd *tcd;
+	unsigned long iflags;
+	struct scatterlist *sg;
+	size_t len;
+	int iter, i;
+
+	if (!list_empty(&mchan->active))
+		return NULL;
+
+	/* currently there is no proper support for scatter/gather */
+	if (sg_len > 1)
+		return NULL;
+
+	for_each_sg(sgl, sg, sg_len, i) {
+		spin_lock_irqsave(&mchan->lock, iflags);
+
+		mdesc = list_first_entry(&mchan->free, struct mpc_dma_desc,
+									node);
+		if (!mdesc) {
+			spin_unlock_irqrestore(&mchan->lock, iflags);
+			/* try to free completed descriptors */
+			mpc_dma_process_completed(mdma);
+			return NULL;
+		}
+
+		list_del(&mdesc->node);
+
+		per_paddr = mchan->per_paddr;
+		tcd_nunits = mchan->tcd_nunits;
+
+		spin_unlock_irqrestore(&mchan->lock, iflags);
+
+		mdesc->error = 0;
+		mdesc->will_access_peripheral = 1;
+		tcd = mdesc->tcd;
+
+		/* Prepare Transfer Control Descriptor for this transaction */
+		memset(tcd, 0, sizeof(struct mpc_dma_tcd));
+
+		if (!IS_ALIGNED(sg_dma_address(sg), 4))
+			return NULL;
+
+		if (direction == DMA_DEV_TO_MEM) {
+			tcd->saddr = per_paddr;
+			tcd->daddr = sg_dma_address(sg);
+			tcd->soff = 0;
+			tcd->doff = 4;
+		} else if (direction == DMA_MEM_TO_DEV) {
+			tcd->saddr = sg_dma_address(sg);
+			tcd->daddr = per_paddr;
+			tcd->soff = 4;
+			tcd->doff = 0;
+		} else {
+			return NULL;
+		}
+		tcd->ssize = MPC_DMA_TSIZE_4;
+		tcd->dsize = MPC_DMA_TSIZE_4;
+
+		len = sg_dma_len(sg);
+
+		if (tcd_nunits)
+			tcd->nbytes = tcd_nunits * 4;
+		else
+			return NULL;
+
+		if (!IS_ALIGNED(len, tcd->nbytes))
+			return NULL;
+
+		iter = len / tcd->nbytes;
+		if (iter > ((1 << 15) - 1)) {   /* maximum biter */
+			return NULL; /* len is too big */
+		} else {
+			/* citer_linkch contains the high bits of iter */
+			tcd->biter = iter & 0x1ff;
+			tcd->biter_linkch = iter >> 9;
+			tcd->citer = tcd->biter;
+			tcd->citer_linkch = tcd->biter_linkch;
+		}
+
+		tcd->e_sg = 0;
+		tcd->d_req = 1;
+
+		/* Place descriptor in prepared list */
+		spin_lock_irqsave(&mchan->lock, iflags);
+		list_add_tail(&mdesc->node, &mchan->prepared);
+		spin_unlock_irqrestore(&mchan->lock, iflags);
+	}
+
+	return &mdesc->desc;
+}
+
+static int mpc_dma_device_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
+				  unsigned long arg)
+{
+	struct mpc_dma_chan *mchan;
+	struct mpc_dma *mdma;
+	struct dma_slave_config *cfg;
+	unsigned long flags;
+
+	mchan = dma_chan_to_mpc_dma_chan(chan);
+	switch (cmd) {
+	case DMA_TERMINATE_ALL:
+		/* disable channel requests */
+		mdma = dma_chan_to_mpc_dma(chan);
+
+		spin_lock_irqsave(&mchan->lock, flags);
+
+		out_8(&mdma->regs->dmacerq, chan->chan_id);
+		list_splice_tail_init(&mchan->prepared, &mchan->free);
+		list_splice_tail_init(&mchan->queued, &mchan->free);
+		list_splice_tail_init(&mchan->active, &mchan->free);
+
+		spin_unlock_irqrestore(&mchan->lock, flags);
+
+		return 0;
+	case DMA_SLAVE_CONFIG:
+		cfg = (void *)arg;
+		if (cfg->src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES &&
+		    cfg->dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
+			return -EINVAL;
+
+		spin_lock_irqsave(&mchan->lock, flags);
+
+		if (cfg->direction == DMA_DEV_TO_MEM) {
+			mchan->per_paddr = cfg->src_addr;
+			mchan->tcd_nunits = cfg->src_maxburst;
+		} else {
+			mchan->per_paddr = cfg->dst_addr;
+			mchan->tcd_nunits = cfg->dst_maxburst;
+		}
+
+		spin_unlock_irqrestore(&mchan->lock, flags);
+
+		return 0;
+	default:
+		return -ENOSYS;
+	}
+
+	return -EINVAL;
+}
+
 static int mpc_dma_probe(struct platform_device *op)
 {
 	struct device_node *dn = op->dev.of_node;
@@ -725,9 +907,12 @@ static int mpc_dma_probe(struct platform_device *op)
 	dma->device_issue_pending = mpc_dma_issue_pending;
 	dma->device_tx_status = mpc_dma_tx_status;
 	dma->device_prep_dma_memcpy = mpc_dma_prep_memcpy;
+	dma->device_prep_slave_sg = mpc_dma_prep_slave_sg;
+	dma->device_control = mpc_dma_device_control;
 
 	INIT_LIST_HEAD(&dma->channels);
 	dma_cap_set(DMA_MEMCPY, dma->cap_mask);
+	dma_cap_set(DMA_SLAVE, dma->cap_mask);
 
 	for (i = 0; i < dma->chancnt; i++) {
 		mchan = &mdma->channels[i];
-- 
1.7.11.3