[PATCH v3 4/4] dmaengine: add union chan_dev for dma_chan::dev for clarity

[Frank.Li@oss.nxp.com]

From: Frank Li <Frank.Li@nxp.com>

The current dma_chan structure contains both "device" and "dev". So

chan->device->dev refers to the DMA engine device.
chan->dev->device refers to the per-channel device instance.

Their similar naming makes the distinction unclear and increases reader
confusion.

Add union dma_chan::chan_dev to make its purpose explicit and clearly
identify it as the per-channel device. After all user switch to chan_dev,
union and dma_chan::dev will be removed.

Update the kernel-doc accordingly. Besides its sysfs usage, the per-channel
device is also used by some DMA engine drivers for IOMMU mapping and
therefore deserves a more accurate description.

No functional change intended.

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
there are other user use it outside drivers/dma/ directory.
---
 drivers/dma/dmaengine.c        | 14 +++++++-------
 drivers/dma/tegra186-gpc-dma.c |  2 +-
 drivers/dma/ti/k3-udma.c       |  4 ++--
 include/linux/dmaengine.h      | 18 +++++++++++++-----
 4 files changed, 23 insertions(+), 15 deletions(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index a7ac2729e4d9d..bb30a9aa54d3f 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1083,8 +1083,8 @@ static int __dma_async_device_channel_register(struct dma_device *device,
 	chan->local = alloc_percpu(typeof(*chan->local));
 	if (!chan->local)
 		return -ENOMEM;
-	chan->dev = kzalloc_obj(*chan->dev);
-	if (!chan->dev) {
+	chan->chan_dev = kzalloc_obj(*chan->chan_dev);
+	if (!chan->chan_dev) {
 		rc = -ENOMEM;
 		goto err_free_local;
 	}
@@ -1103,8 +1103,8 @@ static int __dma_async_device_channel_register(struct dma_device *device,
 
 	dmaengine_chan_dev(chan)->class = &dma_devclass;
 	dmaengine_chan_dev(chan)->parent = device->dev;
-	chan->dev->chan = chan;
-	chan->dev->dev_id = device->dev_id;
+	chan->chan_dev->chan = chan;
+	chan->chan_dev->dev_id = device->dev_id;
 	spin_lock_init(&chan->lock);
 
 	if (!name)
@@ -1122,7 +1122,7 @@ static int __dma_async_device_channel_register(struct dma_device *device,
  err_out_ida:
 	ida_free(&device->chan_ida, chan->chan_id);
  err_free_dev:
-	kfree(chan->dev);
+	kfree(chan->chan_dev);
  err_free_local:
 	free_percpu(chan->local);
 	chan->local = NULL;
@@ -1155,7 +1155,7 @@ static void __dma_async_device_channel_unregister(struct dma_device *device,
 		  __func__, chan->client_count);
 	mutex_lock(&dma_list_mutex);
 	device->chancnt--;
-	chan->dev->chan = NULL;
+	chan->chan_dev->chan = NULL;
 	mutex_unlock(&dma_list_mutex);
 	ida_free(&device->chan_ida, chan->chan_id);
 	device_unregister(dmaengine_chan_dev(chan));
@@ -1290,7 +1290,7 @@ int dma_async_device_register(struct dma_device *device)
 		if (chan->local == NULL)
 			continue;
 		mutex_lock(&dma_list_mutex);
-		chan->dev->chan = NULL;
+		chan->chan_dev->chan = NULL;
 		mutex_unlock(&dma_list_mutex);
 		device_unregister(dmaengine_chan_dev(chan));
 		free_percpu(chan->local);
diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c
index b3327aa35de40..e76c58f213d84 100644
--- a/drivers/dma/tegra186-gpc-dma.c
+++ b/drivers/dma/tegra186-gpc-dma.c
@@ -1554,7 +1554,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
 				return dev_err_probe(chdev, -EINVAL,
 					   "Failed to get stream ID for channel %d\n", tdc->id);
 
-			chan->dev->chan_dma_dev = true;
+			chan->chan_dev->chan_dma_dev = true;
 		}
 
 		/* program stream-id for this channel */
diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
index 49e2d0014d5ed..78a67cb9d6e00 100644
--- a/drivers/dma/ti/k3-udma.c
+++ b/drivers/dma/ti/k3-udma.c
@@ -426,12 +426,12 @@ static void k3_configure_chan_coherency(struct dma_chan *chan, u32 asel)
 
 	if (asel == 0) {
 		/* No special handling for the channel */
-		chan->dev->chan_dma_dev = false;
+		chan->chan_dev->chan_dma_dev = false;
 
 		dev_clear_dma_coherent(chan_dev);
 		chan_dev->dma_parms = NULL;
 	} else if (asel == 14 || asel == 15) {
-		chan->dev->chan_dma_dev = true;
+		chan->chan_dev->chan_dma_dev = true;
 
 		dev_set_dma_coherent(chan_dev);
 		dma_coerce_mask_and_coherent(chan_dev, DMA_BIT_MASK(48));
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 33aa1bfc8fb84..206c5dab96cd7 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -325,7 +325,8 @@ struct dma_router {
  * @lock: protect between config and prepare transfer when driver have not
  *	  implemented callback device_prep_config_sg().
  * @chan_id: channel ID for sysfs
- * @dev: class device for sysfs
+ * @chan_dev: class channel device for sysfs, some device use it for per-channel
+ *            iommu mapping.
  * @name: backlink name for sysfs
  * @dbg_client_name: slave name for debugfs in format:
  *	dev_name(requester's dev):channel name, for example: "2b00000.mcasp:tx"
@@ -351,7 +352,14 @@ struct dma_chan {
 
 	/* sysfs */
 	int chan_id;
-	struct dma_chan_dev *dev;
+	union {
+		struct dma_chan_dev *chan_dev;
+		/*
+		 * please use chan_dev, dev will be removed after all user
+		   switch to chan_dev
+		*/
+		struct dma_chan_dev *dev;
+	};
 	const char *name;
 #ifdef CONFIG_DEBUG_FS
 	char *dbg_client_name;
@@ -532,7 +540,7 @@ struct dma_slave_caps {
 
 static inline const char *dma_chan_name(struct dma_chan *chan)
 {
-	return dev_name(&chan->dev->device);
+	return dev_name(&chan->chan_dev->device);
 }
 
 /**
@@ -1805,12 +1813,12 @@ dmaengine_get_direction_text(enum dma_transfer_direction dir)
 
 static inline struct device *dmaengine_chan_dev(struct dma_chan *chan)
 {
-	return &chan->dev->device;
+	return &chan->chan_dev->device;
 }
 
 static inline struct device *dmaengine_get_dma_device(struct dma_chan *chan)
 {
-	if (chan->dev->chan_dma_dev)
+	if (chan->chan_dev->chan_dma_dev)
 		return dmaengine_chan_dev(chan);
 
 	return chan->device->dev;

-- 
2.43.0