[PATCH v3 06/18] bus: fsl-mc: Add driver dma ownership management

Lu Baolu
2021-12-06T02:00:10Z

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.

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@linux.intel.com>
---
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..3a26421ee3dc 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
+ * @suppress_auto_claim_dma_owner: Disable auto claiming of kernel DMA owner.
+ * 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 suppress_auto_claim_dma_owner;
};

#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..048a837a7116 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->suppress_auto_claim_dma_owner) {
+ ret = iommu_device_set_dma_owner(dev, DMA_OWNER_DMA_API, NULL);
+ 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->suppress_auto_claim_dma_owner)
+ iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
+
+ 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->suppress_auto_claim_dma_owner)
+ iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
}

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