[PATCH v5 06/14] bus: fsl-mc: Add driver dma ownership management

[Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>]

Multiple fsl-mc 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/fsl/mc.h          |  5 +++++
 drivers/bus/fsl-mc/fsl-mc-bus.c | 26 ++++++++++++++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/linux/fsl/mc.h b/include/linux/fsl/mc.h
index e026f6c48b49..e85a5f18104d 100644
--- a/include/linux/fsl/mc.h
+++ b/include/linux/fsl/mc.h
@@ -32,6 +32,10 @@ struct fsl_mc_io;
  * @shutdown: Function called at shutdown time to quiesce the device
  * @suspend: Function called when a device is stopped
  * @resume: Function called when a device is resumed
+ * @no_kernel_api_dma: Device driver doesn't use kernel DMA API for DMA.
+ *		Drivers which don't require DMA or want to manually claim the
+ *		owner type (e.g. userspace driver frameworks) could set this
+ *		flag.
  *
  * Generic DPAA device driver object for device drivers that are registered
  * with a DPRC bus. This structure is to be embedded in each device-specific
@@ -45,6 +49,7 @@ struct fsl_mc_driver {
 	void (*shutdown)(struct fsl_mc_device *dev);
 	int (*suspend)(struct fsl_mc_device *dev, pm_message_t state);
 	int (*resume)(struct fsl_mc_device *dev);
+	bool no_kernel_api_dma;
 };
 
 #define to_fsl_mc_driver(_drv) \
diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index 8fd4a356a86e..9ee85f43822a 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -140,15 +140,36 @@ static int fsl_mc_dma_configure(struct device *dev)
 {
 	struct device *dma_dev = dev;
 	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+	struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(dev->driver);
 	u32 input_id = mc_dev->icid;
+	int ret;
+
+	if (!mc_drv->no_kernel_api_dma) {
+		ret = iommu_device_use_dma_api(dev);
+		if (ret)
+			return ret;
+	}
 
 	while (dev_is_fsl_mc(dma_dev))
 		dma_dev = dma_dev->parent;
 
 	if (dev_of_node(dma_dev))
-		return of_dma_configure_id(dev, dma_dev->of_node, 0, &input_id);
+		ret = of_dma_configure_id(dev, dma_dev->of_node, 0, &input_id);
+	else
+		ret = acpi_dma_configure_id(dev, DEV_DMA_COHERENT, &input_id);
+
+	if (ret && !mc_drv->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
+
+	return ret;
+}
+
+static void fsl_mc_dma_cleanup(struct device *dev)
+{
+	struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(dev->driver);
 
-	return acpi_dma_configure_id(dev, DEV_DMA_COHERENT, &input_id);
+	if (!mc_drv->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
 }
 
 static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
@@ -312,6 +333,7 @@ struct bus_type fsl_mc_bus_type = {
 	.match = fsl_mc_bus_match,
 	.uevent = fsl_mc_bus_uevent,
 	.dma_configure  = fsl_mc_dma_configure,
+	.dma_cleanup = fsl_mc_dma_cleanup,
 	.dev_groups = fsl_mc_dev_groups,
 	.bus_groups = fsl_mc_bus_groups,
 };
-- 
2.25.1