linux-kernel - [PATCH 02/18] dmaengine: Add support for per channel coherency handling

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Date:   Wed, 30 Sep 2020 12:13:56 +0300
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     <vkoul@...nel.org>, <nm@...com>, <ssantosh@...nel.org>,
        <robh+dt@...nel.org>, <vigneshr@...com>
CC:     <dan.j.williams@...el.com>, <t-kristo@...com>,
        <lokeshvutla@...com>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <dmaengine@...r.kernel.org>
Subject: [PATCH 02/18] dmaengine: Add support for per channel coherency handling

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@...com>
---
 include/linux/dmaengine.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index d6197fe875af..182a1a2e7793 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;
 };
 
 /**
@@ -1613,4 +1616,13 @@ 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 */
-- 
Peter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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