On Tue, Feb 24, 2026 at 12:39:00AM +0530, Ekansh Gupta wrote:

Introduce a per-device memory manager for the QDA driver that tracks IOMMU-capable compute context-bank (CB) devices. Each CB device is represented by a qda_iommu_device and registered with a central qda_memory_manager instance owned by qda_dev.

The name makes me expect that this manages memory, but it seems to manage devices and context banks...

The memory manager maintains an xarray of devices and assigns a unique ID to each CB. It also provides basic lifetime management and a workqueue for deferred device removal. qda_cb_setup_device() now allocates a qda_iommu_device for each CB and registers it with the memory manager after DMA configuration succeeds.

qda_init_device() is extended to allocate and initialize the memory manager, while qda_deinit_device() will tear it down in later patches.

"in later patches" makes this extremely hard to review. I had to apply the series to try to navigate the code...

This prepares the QDA driver for fine-grained memory and IOMMU domain management tied to individual CB devices.

Signed-off-by: Ekansh Gupta ekansh.gupta@oss.qualcomm.com

[..]

obj-$(CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS) += qda_compute_bus.o diff --git a/drivers/accel/qda/qda_cb.c b/drivers/accel/qda/qda_cb.c

[..]

@@ -46,6 +52,18 @@ static int qda_cb_setup_device(struct qda_dev *qdev, struct device *cb_dev) rc = dma_set_mask(cb_dev, DMA_BIT_MASK(pa_bits)); if (rc) { qda_err(qdev, "%d bit DMA enable failed: %d\n", pa_bits, rc);

• kfree(iommu_dev);
  

• return rc;
  

• }
• iommu_dev->dev = cb_dev;
• iommu_dev->sid = sid;
• snprintf(iommu_dev->name, sizeof(iommu_dev->name), "qda_iommu_dev_%u", sid);

It's not easy to follow, when you have scattered the code across so many patches and so many files. But I don't think iommu_dev->name is ever used.

• rc = qda_memory_manager_register_device(qdev->iommu_mgr, iommu_dev);
• if (rc) {

• qda_err(qdev, "Failed to register IOMMU device: %d\n", rc);
  

• kfree(iommu_dev);
  

  return rc; }

@@ -127,6 +145,8 @@ int qda_create_cb_device(struct qda_dev *qdev, struct device_node *cb_node) void qda_destroy_cb_device(struct device *cb_dev) { struct iommu_group *group;

• struct qda_iommu_device *iommu_dev;
• struct qda_dev *qdev;

if (!cb_dev) { qda_dbg(NULL, "NULL CB device passed to destroy\n"); @@ -135,6 +155,18 @@ void qda_destroy_cb_device(struct device *cb_dev) qda_dbg(NULL, "Destroying CB device %s\n", dev_name(cb_dev));

• iommu_dev = dev_get_drvdata(cb_dev);

I'm not sure, but I think cb_dev is the struct device allocated in qda_create_cb_device(), but I can not find a place where you set drvdata for this device.

• if (iommu_dev) {

• if (cb_dev->parent) {
  

• 	qdev = dev_get_drvdata(cb_dev->parent);
  

• 	if (qdev && qdev->iommu_mgr) {
  

• 		qda_dbg(NULL, "Unregistering IOMMU device for %s\n",
  

• 			dev_name(cb_dev));
  

• 		qda_memory_manager_unregister_device(qdev->iommu_mgr, iommu_dev);
  

• 	}
  

• }
  

• }
• group = iommu_group_get(cb_dev); if (group) { qda_dbg(NULL, "Removing %s from IOMMU group\n", dev_name(cb_dev));

diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c

[..]

@@ -25,12 +37,46 @@ static void init_device_resources(struct qda_dev *qdev) atomic_set(&qdev->removing, 0); } +static int init_memory_manager(struct qda_dev *qdev) +{

• int ret;
• qda_dbg(qdev, "Initializing IOMMU manager\n");
• qdev->iommu_mgr = kzalloc_obj(*qdev->iommu_mgr, GFP_KERNEL);
• if (!qdev->iommu_mgr)

• return -ENOMEM;
  

• ret = qda_memory_manager_init(qdev->iommu_mgr);
• if (ret) {

• qda_err(qdev, "Failed to initialize memory manager: %d\n", ret);
  

qda_memory_manager_init() already logged 1 error and 1 debug prints if you get here.

• kfree(qdev->iommu_mgr);
  

• qdev->iommu_mgr = NULL;
  

We're going to fail probe, you shouldn't have to clear this.

• return ret;
  

• }
• qda_dbg(qdev, "IOMMU manager initialized successfully\n");
• return 0;

+}

int qda_init_device(struct qda_dev *qdev) {

• int ret;
• init_device_resources(qdev);

• ret = init_memory_manager(qdev);
• if (ret) {

• qda_err(qdev, "IOMMU manager initialization failed: %d\n", ret);
  

And now we have 2 debug prints and two error prints in the log.

• goto err_cleanup_resources;
  

• }
• qda_dbg(qdev, "QDA device initialized successfully\n");

Or, if we get here, you have 8 debug prints.

Please learn how to use kprobe/kretprobe instead of reimplementing it using printk().

return 0;

+err_cleanup_resources:

• cleanup_device_resources(qdev);
• return ret;

} static int __init qda_core_init(void) diff --git a/drivers/accel/qda/qda_drv.h b/drivers/accel/qda/qda_drv.h index eb732b7d8091..2cb97e4eafbf 100644 --- a/drivers/accel/qda/qda_drv.h +++ b/drivers/accel/qda/qda_drv.h @@ -11,6 +11,7 @@ #include <linux/mutex.h> #include <linux/rpmsg.h> #include <linux/xarray.h> +#include "qda_memory_manager.h" /* Driver identification */ #define DRIVER_NAME "qda" @@ -23,6 +24,8 @@ struct qda_dev { struct device *dev; /* Mutex protecting device state */ struct mutex lock;

• /* IOMMU/memory manager */
• struct qda_memory_manager *iommu_mgr; /* Flag indicating device removal in progress */ atomic_t removing; /* Name of the DSP (e.g., "cdsp", "adsp") */

diff --git a/drivers/accel/qda/qda_memory_manager.c b/drivers/accel/qda/qda_memory_manager.c

[..]

+int qda_memory_manager_register_device(struct qda_memory_manager *mem_mgr,

• 		       struct qda_iommu_device *iommu_dev)
  

+{

• int ret;
• u32 id;
• if (!mem_mgr || !iommu_dev || !iommu_dev->dev) {

How could this happen? You call this function from one place, that looks like this:

iommu_dev->dev = cb_dev; iommu_dev->sid = sid; rc = qda_memory_manager_register_device(qdev->iommu_mgr, iommu_dev);

You just allocated in filled out iommu_dev.

Looking up the callstack, we're coming from qda_rpmsg_probe() which just did qda_init_device() which created the qsdev->iommu_mgr.

In other words, these can't possibly be NULL.

• qda_err(NULL, "Invalid parameters for device registration\n");
  

• return -EINVAL;
  

• }
• init_iommu_device_fields(iommu_dev, mem_mgr);
• ret = allocate_device_id(mem_mgr, iommu_dev, &id);
• if (ret) {

• qda_err(NULL, "Failed to allocate device ID: %d (sid=%u)\n", ret, iommu_dev->sid);
  

• return ret;
  

• }
• iommu_dev->id = id;
• qda_dbg(NULL, "Registered device id=%u (sid=%u)\n", id, iommu_dev->sid);
• return 0;

+}

+void qda_memory_manager_unregister_device(struct qda_memory_manager *mem_mgr,

• 			  struct qda_iommu_device *iommu_dev)
  

+{

• if (!mem_mgr || !iommu_dev) {

The one call to this function is wrapped in:

if (iommu_dev) { if (qdev->iommu_mgr) { qda_dbg(NULL, ...); qda_memory_manager_unregister_device(qdev->iommu_mgr, iommu_dev); } }

• qda_err(NULL, "Attempted to unregister invalid device/manager\n");
  

• return;
  

• }
• qda_dbg(NULL, "Unregistering device id=%u (refcount=%u)\n", iommu_dev->id,

• refcount_read(&iommu_dev->refcount));
  

And just before the call to qda_memory_manager_unregister_device() you print a debug log, saying you will call this function.

• if (refcount_read(&iommu_dev->refcount) == 0) {

• xa_erase(&mem_mgr->device_xa, iommu_dev->id);
  

• kfree(iommu_dev);
  

• return;
  

• }
• if (refcount_dec_and_test(&iommu_dev->refcount)) {

• qda_info(NULL, "Device id=%u refcount reached zero, queuing removal\n",
  

• 	 iommu_dev->id);
  

• queue_work(mem_mgr->wq, &iommu_dev->remove_work);
  

• }

+}

[..]

diff --git a/drivers/accel/qda/qda_memory_manager.h b/drivers/accel/qda/qda_memory_manager.h

[..]

+/**

This says "kernel-doc"

• • struct qda_iommu_device - IOMMU device instance for memory management
• • This structure represents a single IOMMU-enabled device managed by the
• • memory manager. Each device can be assigned to a specific process.
• */

+struct qda_iommu_device {

• /* Unique identifier for this IOMMU device */

But this doesn't follow kernel-doc style.

At the end of the series,

./scripts/kernel-doc -none -vv -Wall drivers/accel/qda/

reports 270 warnings.

• u32 id;
• /* Pointer to the underlying device */
• struct device *dev;
• /* Name for the device */
• char name[32];
• /* Spinlock protecting concurrent access to device */
• spinlock_t lock;
• /* Reference counter for device */
• refcount_t refcount;
• /* Work structure for deferred device removal */
• struct work_struct remove_work;
• /* Stream ID for IOMMU transactions */
• u32 sid;
• /* Pointer to parent memory manager */
• struct qda_memory_manager *manager;

+};

Regards, Bjorn