[PATCH v5 04/14] 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.

The device driver may set a new flag (no_kernel_api_dma) to skip calling
iommu_device_use_dma_api() during the binding process. For instance, the
userspace framework drivers (vfio etc.) which need to manually claim
their own dma ownership when assigning the device to userspace.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/platform_device.h |  1 +
 drivers/base/platform.c         | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 17fde717df68..8f0eaafcef47 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 no_kernel_api_dma;
 };
 
 #define to_platform_driver(drv)	(container_of((drv), struct platform_driver, \
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index b4d36b46ab2e..d5171e44d903 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"
@@ -1451,9 +1452,16 @@ static void platform_shutdown(struct device *_dev)
 
 static int platform_dma_configure(struct device *dev)
 {
+	struct platform_driver *drv = to_platform_driver(dev->driver);
 	enum dev_dma_attr attr;
 	int ret = 0;
 
+	if (!drv->no_kernel_api_dma) {
+		ret = iommu_device_use_dma_api(dev);
+		if (ret)
+			return ret;
+	}
+
 	if (dev->of_node) {
 		ret = of_dma_configure(dev, dev->of_node, true);
 	} else if (has_acpi_companion(dev)) {
@@ -1461,9 +1469,20 @@ static int platform_dma_configure(struct device *dev)
 		ret = acpi_dma_configure(dev, attr);
 	}
 
+	if (ret && !drv->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
+
 	return ret;
 }
 
+static void platform_dma_cleanup(struct device *dev)
+{
+	struct platform_driver *drv = to_platform_driver(dev->driver);
+
+	if (!drv->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
+}
+
 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
@@ -1478,6 +1497,7 @@ struct bus_type platform_bus_type = {
 	.remove		= platform_remove,
 	.shutdown	= platform_shutdown,
 	.dma_configure	= platform_dma_configure,
+	.dma_cleanup	= platform_dma_cleanup,
 	.pm		= &platform_dev_pm_ops,
 };
 EXPORT_SYMBOL_GPL(platform_bus_type);
-- 
2.25.1