[PATCH v2 04/17] driver core: platform: Add driver dma ownership management

[Lu Baolu]

Multiple platform devices may be placed in the same IOMMU group because
they cannot be isolated from each other. These devices must either be
entirely under kernel control or userspace control, never a mixture. This
checks and sets DMA ownership during driver binding, and release the
ownership during driver unbinding.

Driver may set a new flag (suppress_auto_claim_dma_owner) to disable auto
claiming DMA_OWNER_DMA_API ownership in the binding process. For instance,
the userspace framework drivers (vfio etc.) which need to manually claim
DMA_OWNER_PRIVATE_DOMAIN_USER when assigning a device to userspace.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/platform_device.h |  1 +
 drivers/base/platform.c         | 30 +++++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 7c96f169d274..779bcf2a851c 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -210,6 +210,7 @@ struct platform_driver {
 	struct device_driver driver;
 	const struct platform_device_id *id_table;
 	bool prevent_deferred_probe;
+	bool suppress_auto_claim_dma_owner;
 };
 
 #define to_platform_driver(drv)	(container_of((drv), struct platform_driver, \
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 598acf93a360..df4b385c8a52 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -30,6 +30,7 @@
 #include <linux/property.h>
 #include <linux/kmemleak.h>
 #include <linux/types.h>
+#include <linux/iommu.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -1465,6 +1466,32 @@ int platform_dma_configure(struct device *dev)
 	return ret;
 }
 
+static int _platform_dma_configure(struct device *dev)
+{
+	struct platform_driver *drv = to_platform_driver(dev->driver);
+	int ret;
+
+	if (!drv->suppress_auto_claim_dma_owner) {
+		ret = iommu_device_set_dma_owner(dev, DMA_OWNER_DMA_API, NULL);
+		if (ret)
+			return ret;
+	}
+
+	ret = platform_dma_configure(dev);
+	if (ret && !drv->suppress_auto_claim_dma_owner)
+		iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
+
+	return ret;
+}
+
+static void _platform_dma_unconfigure(struct device *dev)
+{
+	struct platform_driver *drv = to_platform_driver(dev->driver);
+
+	if (!drv->suppress_auto_claim_dma_owner)
+		iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
+}
+
 static const struct dev_pm_ops platform_dev_pm_ops = {
 	SET_RUNTIME_PM_OPS(pm_generic_runtime_suspend, pm_generic_runtime_resume, NULL)
 	USE_PLATFORM_PM_SLEEP_OPS
@@ -1478,7 +1505,8 @@ struct bus_type platform_bus_type = {
 	.probe		= platform_probe,
 	.remove		= platform_remove,
 	.shutdown	= platform_shutdown,
-	.dma_configure	= platform_dma_configure,
+	.dma_configure	= _platform_dma_configure,
+	.dma_unconfigure = _platform_dma_unconfigure,
 	.pm		= &platform_dev_pm_ops,
 };
 EXPORT_SYMBOL_GPL(platform_bus_type);
-- 
2.25.1