[PATCH v9 03/11] dmaengine: qcom: bam_dma: implement support for BAM locking

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Use metadata operations in DMA descriptors to allow BAM users to pass
additional information to the engine. To that end: define a new
structure - struct bam_desc_metadata - as a medium and define two new
commands: for locking and unlocking the BAM respectively. Handle the
locking in the .attach() callback.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/dma/qcom/bam_dma.c       | 59 +++++++++++++++++++++++++++++++++++++++-
 include/linux/dma/qcom_bam_dma.h | 12 ++++++++
 2 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index c9ae1fffe44d79c5eb59b8bbf7f147a8fa3aa0bd..d1dc80b29818897b333cd223ec7306a169cc51fd 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -30,6 +30,7 @@
 #include <linux/module.h>
 #include <linux/interrupt.h>
 #include <linux/dma-mapping.h>
+#include <linux/dma/qcom_bam_dma.h>
 #include <linux/scatterlist.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
@@ -391,6 +392,8 @@ struct bam_chan {
 	struct list_head desc_list;
 
 	struct list_head node;
+
+	bool bam_locked;
 };
 
 static inline struct bam_chan *to_bam_chan(struct dma_chan *common)
@@ -655,6 +658,53 @@ static int bam_slave_config(struct dma_chan *chan,
 	return 0;
 }
 
+static int bam_metadata_attach(struct dma_async_tx_descriptor *desc, void *data, size_t len)
+{
+	struct virt_dma_desc *vd = container_of(desc, struct virt_dma_desc, tx);
+	struct bam_async_desc *async_desc = container_of(vd, struct bam_async_desc,  vd);
+	struct bam_desc_hw *hw_desc = async_desc->desc;
+	struct bam_desc_metadata *metadata = data;
+	struct bam_chan *bchan = to_bam_chan(metadata->chan);
+	struct bam_device *bdev = bchan->bdev;
+
+	if (!data)
+		return -EINVAL;
+
+	if (metadata->op == BAM_META_CMD_LOCK || metadata->op == BAM_META_CMD_UNLOCK) {
+		if (!bdev->dev_data->bam_pipe_lock)
+			return -EOPNOTSUPP;
+
+		/* Expecting a dummy write when locking, only one descriptor allowed. */
+		if (async_desc->num_desc != 1)
+			return -EINVAL;
+	}
+
+	switch (metadata->op) {
+	case BAM_META_CMD_LOCK:
+		if (bchan->bam_locked)
+			return -EBUSY;
+
+		hw_desc->flags |= DESC_FLAG_LOCK;
+		bchan->bam_locked = true;
+		break;
+	case BAM_META_CMD_UNLOCK:
+		if (!bchan->bam_locked)
+			return -EPERM;
+
+		hw_desc->flags |= DESC_FLAG_UNLOCK;
+		bchan->bam_locked = false;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static struct dma_descriptor_metadata_ops bam_metadata_ops = {
+	.attach = bam_metadata_attach,
+};
+
 /**
  * bam_prep_slave_sg - Prep slave sg transaction
  *
@@ -671,6 +721,7 @@ static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
 	void *context)
 {
 	struct bam_chan *bchan = to_bam_chan(chan);
+	struct dma_async_tx_descriptor *tx_desc;
 	struct bam_device *bdev = bchan->bdev;
 	struct bam_async_desc *async_desc;
 	struct scatterlist *sg;
@@ -732,7 +783,12 @@ static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan,
 		} while (remainder > 0);
 	}
 
-	return vchan_tx_prep(&bchan->vc, &async_desc->vd, flags);
+	tx_desc = vchan_tx_prep(&bchan->vc, &async_desc->vd, flags);
+	if (!tx_desc)
+		return NULL;
+
+	tx_desc->metadata_ops = &bam_metadata_ops;
+	return tx_desc;
 }
 
 /**
@@ -1372,6 +1428,7 @@ static int bam_dma_probe(struct platform_device *pdev)
 	bdev->common.device_terminate_all = bam_dma_terminate_all;
 	bdev->common.device_issue_pending = bam_issue_pending;
 	bdev->common.device_tx_status = bam_tx_status;
+	bdev->common.desc_metadata_modes = DESC_METADATA_CLIENT;
 	bdev->common.dev = bdev->dev;
 
 	ret = dma_async_device_register(&bdev->common);
diff --git a/include/linux/dma/qcom_bam_dma.h b/include/linux/dma/qcom_bam_dma.h
index 68fc0e643b1b97fe4520d5878daa322b81f4f559..dd30bb9c520fac7bd98c5a47e56a5a286331461a 100644
--- a/include/linux/dma/qcom_bam_dma.h
+++ b/include/linux/dma/qcom_bam_dma.h
@@ -8,6 +8,8 @@
 
 #include <asm/byteorder.h>
 
+struct dma_chan;
+
 /*
  * This data type corresponds to the native Command Element
  * supported by BAM DMA Engine.
@@ -34,6 +36,16 @@ enum bam_command_type {
 	BAM_READ_COMMAND,
 };
 
+enum bam_desc_metadata_op {
+	BAM_META_CMD_LOCK = 1,
+	BAM_META_CMD_UNLOCK,
+};
+
+struct bam_desc_metadata {
+	enum bam_desc_metadata_op op;
+	struct dma_chan *chan;
+};
+
 /*
  * prep_bam_ce_le32 - Wrapper function to prepare a single BAM command
  * element with the data already in le32 format.

-- 
2.51.0