[PATCH v3 08/20] dmaengine: Add support for per channel coherency handling

Peter Ujfalusi
2020-12-08T09:06:41Z

If the DMA device supports per channel coherency configuration (a channel
can be configured to have coherent or not coherent view) then a single
device (the DMA controller's device) can not be used for dma_api for all
channels as channels can have different coherency.

Introduce custom_dma_mapping flag for the dma_chan and a new helper to get
the device pointer to be used for dma_api for the given channel.

Client drivers should be updated to be able to support per channel
coherency by:

- dma_map_single(chan->device->dev, ptr, size, DMA_TO_DEVICE);
+ struct device *dma_dev = dmaengine_get_dma_device(chan);
+
+ dma_map_single(dma_dev, ptr, size, DMA_TO_DEVICE);

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
include/linux/dmaengine.h | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index aed44888cad3..68130f5f599e 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -357,11 +357,14 @@ struct dma_chan {
* @chan: driver channel device
* @device: sysfs device
* @dev_id: parent dma_device dev_id
+ * @chan_dma_dev: The channel is using custom/different dma-mapping
+ * compared to the parent dma_device
*/
struct dma_chan_dev {
struct dma_chan *chan;
struct device device;
int dev_id;
+ bool chan_dma_dev;
};

/**
@@ -1618,4 +1621,13 @@ dmaengine_get_direction_text(enum dma_transfer_direction dir)
return "invalid";
}
}
+
+static inline struct device *dmaengine_get_dma_device(struct dma_chan *chan)
+{
+ if (chan->dev->chan_dma_dev)
+ return &chan->dev->device;
+
+ return chan->device->dev;
+}
+
#endif /* DMAENGINE_H */