[PATCH v2 6/6] dmaengine: jz4780: Support bidirectional I/O on one channel

[Paul Cercueil <paul@xxxxxxxxxxxxxxx>]

For some devices with only half-duplex capabilities, it doesn't make
much sense to use one DMA channel per direction, as both channels will
never be active at the same time.

Add support for bidirectional I/O on DMA channels. The client drivers
can then request a "tx-rx" DMA channel which will be used for both
directions.

Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---
 drivers/dma/dma-jz4780.c | 48 ++++++++++++++++++++++++++--------------
 1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index c8c4bbd57d14..fc513eb2b289 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -122,6 +122,7 @@ struct jz4780_dma_desc {
 	dma_addr_t desc_phys;
 	unsigned int count;
 	enum dma_transaction_type type;
+	u32 transfer_type;
 	u32 status;
 };
 
@@ -130,7 +131,7 @@ struct jz4780_dma_chan {
 	unsigned int id;
 	struct dma_pool *desc_pool;
 
-	u32 transfer_type;
+	u32 transfer_type_tx, transfer_type_rx;
 	u32 transfer_shift;
 	struct dma_slave_config	config;
 
@@ -157,7 +158,7 @@ struct jz4780_dma_dev {
 };
 
 struct jz4780_dma_filter_data {
-	u32 transfer_type;
+	u32 transfer_type_tx, transfer_type_rx;
 	int channel;
 };
 
@@ -226,9 +227,10 @@ static inline void jz4780_dma_chan_disable(struct jz4780_dma_dev *jzdma,
 		jz4780_dma_ctrl_writel(jzdma, JZ_DMA_REG_DCKEC, BIT(chn));
 }
 
-static struct jz4780_dma_desc *jz4780_dma_desc_alloc(
-	struct jz4780_dma_chan *jzchan, unsigned int count,
-	enum dma_transaction_type type)
+static struct jz4780_dma_desc *
+jz4780_dma_desc_alloc(struct jz4780_dma_chan *jzchan, unsigned int count,
+		      enum dma_transaction_type type,
+		      enum dma_transfer_direction direction)
 {
 	struct jz4780_dma_desc *desc;
 
@@ -248,6 +250,12 @@ static struct jz4780_dma_desc *jz4780_dma_desc_alloc(
 
 	desc->count = count;
 	desc->type = type;
+
+	if (direction == DMA_DEV_TO_MEM)
+		desc->transfer_type = jzchan->transfer_type_rx;
+	else
+		desc->transfer_type = jzchan->transfer_type_tx;
+
 	return desc;
 }
 
@@ -361,7 +369,7 @@ static struct dma_async_tx_descriptor *jz4780_dma_prep_slave_sg(
 	unsigned int i;
 	int err;
 
-	desc = jz4780_dma_desc_alloc(jzchan, sg_len, DMA_SLAVE);
+	desc = jz4780_dma_desc_alloc(jzchan, sg_len, DMA_SLAVE, direction);
 	if (!desc)
 		return NULL;
 
@@ -410,7 +418,7 @@ static struct dma_async_tx_descriptor *jz4780_dma_prep_dma_cyclic(
 
 	periods = buf_len / period_len;
 
-	desc = jz4780_dma_desc_alloc(jzchan, periods, DMA_CYCLIC);
+	desc = jz4780_dma_desc_alloc(jzchan, periods, DMA_CYCLIC, direction);
 	if (!desc)
 		return NULL;
 
@@ -455,14 +463,14 @@ static struct dma_async_tx_descriptor *jz4780_dma_prep_dma_memcpy(
 	struct jz4780_dma_desc *desc;
 	u32 tsz;
 
-	desc = jz4780_dma_desc_alloc(jzchan, 1, DMA_MEMCPY);
+	desc = jz4780_dma_desc_alloc(jzchan, 1, DMA_MEMCPY, 0);
 	if (!desc)
 		return NULL;
 
 	tsz = jz4780_dma_transfer_size(jzchan, dest | src | len,
 				       &jzchan->transfer_shift);
 
-	jzchan->transfer_type = JZ_DMA_DRT_AUTO;
+	desc->transfer_type = JZ_DMA_DRT_AUTO;
 
 	desc->desc[0].dsa = src;
 	desc->desc[0].dta = dest;
@@ -528,7 +536,7 @@ static void jz4780_dma_begin(struct jz4780_dma_chan *jzchan)
 
 	/* Set transfer type. */
 	jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DRT,
-			      jzchan->transfer_type);
+			      jzchan->desc->transfer_type);
 
 	/*
 	 * Set the transfer count. This is redundant for a descriptor-driven
@@ -788,7 +796,8 @@ static bool jz4780_dma_filter_fn(struct dma_chan *chan, void *param)
 		return false;
 	}
 
-	jzchan->transfer_type = data->transfer_type;
+	jzchan->transfer_type_tx = data->transfer_type_tx;
+	jzchan->transfer_type_rx = data->transfer_type_rx;
 
 	return true;
 }
@@ -800,11 +809,17 @@ static struct dma_chan *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
 	dma_cap_mask_t mask = jzdma->dma_device.cap_mask;
 	struct jz4780_dma_filter_data data;
 
-	if (dma_spec->args_count != 2)
+	if (dma_spec->args_count == 2) {
+		data.transfer_type_tx = dma_spec->args[0];
+		data.transfer_type_rx = dma_spec->args[0];
+		data.channel = dma_spec->args[1];
+	} else if (dma_spec->args_count == 3) {
+		data.transfer_type_tx = dma_spec->args[0];
+		data.transfer_type_rx = dma_spec->args[1];
+		data.channel = dma_spec->args[2];
+	} else {
 		return NULL;
-
-	data.transfer_type = dma_spec->args[0];
-	data.channel = dma_spec->args[1];
+	}
 
 	if (data.channel > -1) {
 		if (data.channel >= jzdma->soc_data->nb_channels) {
@@ -822,7 +837,8 @@ static struct dma_chan *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
 			return NULL;
 		}
 
-		jzdma->chan[data.channel].transfer_type = data.transfer_type;
+		jzdma->chan[data.channel].transfer_type_tx = data.transfer_type_tx;
+		jzdma->chan[data.channel].transfer_type_rx = data.transfer_type_rx;
 
 		return dma_get_slave_channel(
 			&jzdma->chan[data.channel].vchan.chan);
-- 
2.33.0