[PATCH/RFC] iommu/ipmmu-vmsa: IPMMU SYS-DMAC iova mapping workaround

[Magnus Damm <magnus.damm@gmail.com>]

From: Magnus Damm <damm+renesas@opensource.se>

Here's some prototype code that works around the lack of software
support for mapping I/O devices to the SYS-DMAC hardware via the
DMA Engine framework when using IOMMU.

The code itself is one big layering violation that goes through
the DT and unconditionally maps I/O devices using DMACs via the
IPMMU device instance into iova space with a 1:1 mapping.

This very short term prototype will for instance automatically make
the SCIF serial port function with the IPMMU hardware in case the
SYS-DMAC is hooked up to the IPMMU device.

Not to be confused with the more long term solution to allow the
DMA Engine framework to map I/O device memory dynamically.

Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
---

 Applies on top of: renesas-drivers-2016-09-13-v4.8-rc6

 drivers/iommu/ipmmu-vmsa.c |   75 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

--- 0001/drivers/iommu/ipmmu-vmsa.c
+++ work/drivers/iommu/ipmmu-vmsa.c	2016-09-20 20:03:37.620607110 +0900
@@ -19,6 +19,7 @@
 #include <linux/iommu.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_iommu.h>
 #include <linux/platform_device.h>
 #include <linux/sizes.h>
@@ -625,6 +626,78 @@ static void ipmmu_domain_free(struct iom
 	kfree(domain);
 }
 
+static void ipmmu_workaround_map(struct iommu_domain *io_domain,
+				 struct device *dma_dev, struct resource *res)
+{
+	phys_addr_t phys_addr;
+
+	dev_info(dma_dev, "map %pr\n", res);
+
+	phys_addr = iommu_iova_to_phys(io_domain, res->start);
+	if (phys_addr)
+		return;
+
+	iommu_map(io_domain, res->start, res->start,
+		  ALIGN(resource_size(res), SZ_4K),
+		  IOMMU_READ | IOMMU_WRITE);
+}
+
+static void ipmmu_workaround_dt(struct iommu_domain *io_domain,
+				struct device *dev,
+				void (*match)(struct iommu_domain *io_domain,
+					      struct device *dma_dev,
+					      struct resource *res))
+{
+	struct device_node *np = NULL;
+	struct of_phandle_args dma_spec;
+	struct resource r;
+	int i, cnt;
+	bool found;
+
+	/* Locate I/O devices using the DMAC and map their registers */
+	while ((np = of_find_all_nodes(np))) {
+		if (!of_find_property(np, "dmas", NULL))
+			continue;
+
+		cnt = of_property_count_strings(np, "dma-names");
+		if (cnt < 0)
+			continue;
+
+		found = false;
+		for (i = 0; i < cnt; i++) {
+			if (of_parse_phandle_with_args(np, "dmas",
+						       "#dma-cells", i,
+						       &dma_spec))
+				continue;
+
+			if (dma_spec.np == dev->of_node)
+				found = true;
+
+			of_node_put(dma_spec.np);
+		}
+
+		if (!found)
+			continue;
+
+		i = 0;
+		while (!of_address_to_resource(np, i, &r)) {
+			match(io_domain, dev, &r);
+			i++;
+		}
+	}
+}
+
+static void ipmmu_workaround(struct iommu_domain *io_domain,
+			     struct device *dev)
+{
+	/* only apply workaround for DMA controllers */
+	if (!strstr(dev_name(dev), "dma-controller"))
+		return;
+
+	dev_info(dev, "Adding iommu workaround to map I/O devices for DMACs\n");
+	ipmmu_workaround_dt(io_domain, dev, ipmmu_workaround_map);
+}
+
 static int ipmmu_attach_device(struct iommu_domain *io_domain,
 			       struct device *dev)
 {
@@ -678,6 +751,8 @@ static int ipmmu_attach_device(struct io
 	if (ret < 0)
 		return ret;
 
+	ipmmu_workaround(io_domain, dev);
+
 	for (i = 0; i < archdata->num_utlbs; ++i)
 		ipmmu_utlb_enable(domain, archdata->utlbs[i]);