[PATCH 1/1] dmaengine: qcom: bam_dma: Add support for metadata

[Sireesh Kodali <sireeshkodali1@gmail.com>]

Some devices (like the IPA block) do not send the size of the DMA
transaction in band. Instead, the IPA driver needs to get the size of
the DMA transaction from the size of the BAM driver. This commit adds
support for attaching a pointer using the dmaengine API, to which it
will write the size of the DMA transaction.

Signed-off-by: Sireesh Kodali <sireeshkodali1@gmail.com>
---
 drivers/dma/qcom/bam_dma.c | 74 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index cebec638a994..911c0f2e88a2 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -71,6 +71,11 @@ struct bam_async_desc {
 
 	struct bam_desc_hw *curr_desc;
 
+	/* first descriptor position in fifo */
+	size_t fifo_index;
+	void *metadata;
+	size_t meta_len;
+
 	/* list node for the desc in the bam_chan list of descriptors */
 	struct list_head desc_node;
 	enum dma_transfer_direction dir;
@@ -593,6 +598,65 @@ static int bam_slave_config(struct dma_chan *chan,
 	return 0;
 }
 
+/**
+ * bam_update_metadata - update metadata buffer
+ * @async_desc: BAM async descriptior
+ * @fifo: BAM FIFO to read metadata from
+ *
+ * Updates metadata buffer (transfer size) based on values
+ * read from FIFO descriptors
+ */
+
+static void bam_update_metadata(struct bam_async_desc *async_desc,
+				struct bam_desc_hw *fifo)
+{
+	unsigned int len = 0, i;
+
+	if (!async_desc->metadata)
+		return;
+
+	for (i = 0; i < async_desc->xfer_len; ++i) {
+		unsigned int pos = (i + async_desc->fifo_index) % MAX_DESCRIPTORS;
+
+		len += fifo[pos].size;
+	}
+
+	switch (async_desc->meta_len)  {
+	case 4:
+		*((u32 *)async_desc->metadata) = len;
+		break;
+	case 8:
+		*((u64 *)async_desc->metadata) = len;
+		break;
+	}
+}
+
+/**
+ * bam_attach_metadata - attach metadata buffer to the async descriptor
+ * @desc: async descriptor
+ * @data: buffer pointer
+ * @len: length of passed buffer
+ */
+static int bam_attach_metadata(struct dma_async_tx_descriptor *desc, void *data,
+			       size_t len)
+{
+	struct bam_async_desc *async_desc;
+
+	if (!data || !(len == 2 || len == 4 || len == 8))
+		return -EINVAL;
+
+	async_desc = container_of(desc, struct bam_async_desc, vd.tx);
+
+	async_desc->metadata = data;
+	async_desc->meta_len = len;
+
+	return 0;
+}
+
+static struct dma_descriptor_metadata_ops metadata_ops = {
+	.attach = bam_attach_metadata,
+};
+
 /**
  * bam_prep_slave_sg - Prep slave sg transaction
  *
@@ -672,6 +736,8 @@ static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
 		} while (remainder > 0);
 	}
 
+	async_desc->vd.tx.metadata_ops = &metadata_ops;
+
 	return vchan_tx_prep(&bchan->vc, &async_desc->vd, flags);
 }
 
@@ -839,6 +905,11 @@ static u32 process_channel_irqs(struct bam_device *bdev)
 			 * it gets restarted by the tasklet
 			 */
 			if (!async_desc->num_desc) {
+				struct bam_desc_hw *fifo = PTR_ALIGN(bchan->fifo_virt,
+						sizeof(struct bam_desc_hw));
+
+				bam_update_metadata(async_desc, fifo);
+
 				vchan_cookie_complete(&async_desc->vd);
 			} else {
 				list_add(&async_desc->vd.node,
@@ -1053,6 +1124,8 @@ static void bam_start_dma(struct bam_chan *bchan)
 			       sizeof(struct bam_desc_hw));
 		}
 
+		async_desc->fifo_index = bchan->tail;
+
 		bchan->tail += async_desc->xfer_len;
 		bchan->tail %= MAX_DESCRIPTORS;
 		list_add_tail(&async_desc->desc_node, &bchan->desc_list);
@@ -1331,6 +1404,7 @@ static int bam_dma_probe(struct platform_device *pdev)
 	bdev->common.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
 	bdev->common.src_addr_widths = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	bdev->common.dst_addr_widths = DMA_SLAVE_BUSWIDTH_4_BYTES;
+	bdev->common.desc_metadata_modes = DESC_METADATA_CLIENT;
 	bdev->common.device_alloc_chan_resources = bam_alloc_chan;
 	bdev->common.device_free_chan_resources = bam_free_chan;
 	bdev->common.device_prep_slave_sg = bam_prep_slave_sg;
-- 
2.33.0