media: sun4i-csi: Deal with DRAM offset

On Allwinner SoCs, some high memory bandwidth devices do DMA directly
over the memory bus (called MBUS), instead of the system bus. These
devices include the CSI camera sensor interface, video (codec) engine,
display subsystem, etc.. The memory bus has a different addressing
scheme without the DRAM starting offset.

Deal with this using the "interconnects" property from the device tree,
or if that is not available, set dev->dma_pfn_offset to PHYS_PFN_OFFSET.

Fixes: 577bbf23 ("media: sunxi: Add A10 CSI driver")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/sunxi/sun4i-csi/sun4i_csi.c

@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/of_graph.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
@@ -155,6 +156,27 @@ static int sun4i_csi_probe(struct platform_device *pdev)
 	subdev = &csi->subdev;
 	vdev = &csi->vdev;
 
+	/*
+	 * On Allwinner SoCs, some high memory bandwidth devices do DMA
+	 * directly over the memory bus (called MBUS), instead of the
+	 * system bus. The memory bus has a different addressing scheme
+	 * without the DRAM starting offset.
+	 *
+	 * In some cases this can be described by an interconnect in
+	 * the device tree. In other cases where the hardware is not
+	 * fully understood and the interconnect is left out of the
+	 * device tree, fall back to a default offset.
+	 */
+	if (of_find_property(csi->dev->of_node, "interconnects", NULL)) {
+		ret = of_dma_configure(csi->dev, csi->dev->of_node, true);
+		if (ret)
+			return ret;
+	} else {
+#ifdef PHYS_PFN_OFFSET
+		csi->dev->dma_pfn_offset = PHYS_PFN_OFFSET;
+#endif
+	}
+
 	csi->mdev.dev = csi->dev;
 	strscpy(csi->mdev.model, "Allwinner Video Capture Device",
 		sizeof(csi->mdev.model));