[PATCH v6 22/24] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

[Serge Semin <Sergey.Semin@baikalelectronics.ru>]

DW eDMA doesn't perform any translation of the traffic generated on the
CPU/Application side. It just generates read/write AXI-bus requests with
the specified addresses. But in case if the dma-ranges DT-property is
specified for a platform device node, Linux will use it to create a
mapping the PCIe-bus regions into the CPU memory ranges. This isn't what
we want for the eDMA embedded into the locally accessed DW PCIe Root Port
and End-point. In order to work that around let's set the chan_dma_dev
flag for each DW eDMA channel thus forcing the client drivers to getting a
custom dma-ranges-less parental device for the mappings.

Note it will only work for the client drivers using the
dmaengine_get_dma_device() method to get the parental DMA device.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>

---

Changelog v2:
- Fix the comment a bit to being clearer. (@Manivannan)

Changelog v3:
- Conditionally set dchan->dev->device.dma_coherent field since it can
  be missing on some platforms. (@Manivannan)
- Remove Manivannan' rb and tb tags since the patch content has been
  changed.

Changelog v6:
- Directly call *_dma_configure() method on the child device used for
  the DMA buffers mapping. (@Robin)
- Explicitly set the DMA-mask of the child device in the channel
  allocation proecedure. (@Robin)
- Drop @Manivannan and @Vinod rb- and ab-tags due to significant patch
  content change.
---
 drivers/dma/dw-edma/dw-edma-core.c | 44 ++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index e3671bfbe186..846518509753 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -6,9 +6,11 @@
  * Author: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
  */
 
+#include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/of_device.h>
 #include <linux/dmaengine.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
@@ -711,10 +713,52 @@ static irqreturn_t dw_edma_interrupt_common(int irq, void *data)
 static int dw_edma_alloc_chan_resources(struct dma_chan *dchan)
 {
 	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
+	struct device *dev = chan->dw->chip->dev;
+	int ret;
 
 	if (chan->status != EDMA_ST_IDLE)
 		return -EBUSY;
 
+	/* Bypass the dma-ranges based memory regions mapping for the eDMA
+	 * controlled from the CPU/Application side since in that case
+	 * the local memory address is left untranslated.
+	 */
+	if (chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) {
+		ret = dma_coerce_mask_and_coherent(&dchan->dev->device,
+						   DMA_BIT_MASK(64));
+		if (ret) {
+			ret = dma_coerce_mask_and_coherent(&dchan->dev->device,
+							   DMA_BIT_MASK(32));
+			if (ret)
+				return ret;
+		}
+
+		if (dev_of_node(dev)) {
+			struct device_node *node = dev_of_node(dev);
+
+			ret = of_dma_configure(&dchan->dev->device, node, true);
+		} else if (has_acpi_companion(dev)) {
+			struct acpi_device *adev = to_acpi_device_node(dev->fwnode);
+
+			ret = acpi_dma_configure(&dchan->dev->device,
+						 acpi_get_dma_attr(adev));
+		} else {
+			ret = -EINVAL;
+		}
+
+		if (ret)
+			return ret;
+
+		if (dchan->dev->device.dma_range_map) {
+			kfree(dchan->dev->device.dma_range_map);
+			dchan->dev->device.dma_range_map = NULL;
+		}
+
+		dchan->dev->chan_dma_dev = true;
+	} else {
+		dchan->dev->chan_dma_dev = false;
+	}
+
 	return 0;
 }
 
-- 
2.38.0