[RFC PATCH v2 1/4] bus: fsl-mc: add custom .dma_configure implementation

[laurentiu.tudor@xxxxxxx]

From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>

The devices on this bus are not discovered by way of device tree
but by queries to the firmware. It makes little sense to trick the
generic of layer into thinking that these devices are of related so
that we can get our dma configuration. Instead of doing that, add
our custom dma configuration implementation.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
---
 drivers/bus/fsl-mc/fsl-mc-bus.c | 50 ++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index a0f8854acb3a..a3d25c1d4ff8 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -18,6 +18,7 @@
 #include <linux/bitops.h>
 #include <linux/msi.h>
 #include <linux/dma-mapping.h>
+#include <linux/iommu.h>
 
 #include "fsl-mc-private.h"
 
@@ -130,11 +131,58 @@ static int fsl_mc_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
 static int fsl_mc_dma_configure(struct device *dev)
 {
 	struct device *dma_dev = dev;
+	struct iommu_fwspec *fwspec;
+	const struct iommu_ops *iommu_ops;
+	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+	int ret;
+	u32 icid;
+
+	/* Skip DMA setup for devices that are not DMA masters */
+	if (dev->type == &fsl_mc_bus_dpmcp_type ||
+	    dev->type == &fsl_mc_bus_dpbp_type ||
+	    dev->type == &fsl_mc_bus_dpcon_type ||
+	    dev->type == &fsl_mc_bus_dpio_type)
+		return 0;
 
 	while (dev_is_fsl_mc(dma_dev))
 		dma_dev = dma_dev->parent;
 
-	return of_dma_configure(dev, dma_dev->of_node, 0);
+	fwspec = dev_iommu_fwspec_get(dma_dev);
+	if (!fwspec)
+		return -ENODEV;
+	iommu_ops = iommu_ops_from_fwnode(fwspec->iommu_fwnode);
+	if (!iommu_ops)
+		return -ENODEV;
+
+	ret = iommu_fwspec_init(dev, fwspec->iommu_fwnode, iommu_ops);
+	if (ret)
+		return ret;
+
+	if (iommu_ops->of_xlate) {
+		struct of_phandle_args iommu_spec = {
+			.np = fwspec->iommu_fwnode->dev->of_node,
+			.args[0] = mc_dev->icid,
+			.args_count = 1
+		};
+
+		ret = iommu_ops->of_xlate(dev, &iommu_spec);
+		if (ret) {
+			iommu_fwspec_free(dev);
+			return ret;
+		}
+	}
+
+	if (!device_iommu_mapped(dev)) {
+		ret = iommu_probe_device(dev);
+		if (ret) {
+			iommu_fwspec_free(dev);
+			return ret;
+		}
+	}
+
+	arch_setup_dma_ops(dev, 0, *dma_dev->dma_mask + 1, iommu_ops, true);
+
+	return 0;
 }
 
 static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
-- 
2.17.1