[PATCH RFC 10/18] accel/qda: Add DMA-backed GEM objects and memory manager integration

[Ekansh Gupta]

Introduce DMA-backed GEM buffer objects for the QDA accelerator
driver and integrate them with the existing memory manager and IOMMU
device abstraction.

A new qda_gem_obj structure wraps drm_gem_object and tracks the
kernel virtual address, DMA address, size and owning qda_iommu_device.
qda_gem_create_object() allocates a GEM object, aligns the requested
size, and uses qda_memory_manager_alloc() to obtain DMA-coherent
memory from a per-process IOMMU device. The GEM object implements
a .mmap callback that validates the VMA offset and calls into
qda_dma_mmap(), which maps the DMA memory into userspace and sets
appropriate VMA flags.

The DMA backend is implemented in qda_memory_dma.c, which allocates
and frees coherent memory via dma_alloc_coherent() and
dma_free_coherent(), while storing a SID-prefixed DMA address in
the GEM object for later use by DSP firmware. The memory manager
is extended to maintain a mapping from processes to IOMMU devices
using qda_file_priv and a process_assignment_lock, and provides
qda_memory_manager_alloc() and qda_memory_manager_free() helpers
for GEM allocations.

This patch lays the groundwork for GEM allocation and mmap IOCTLs
as well as future PRIME and job submission support for QDA buffers.

Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
---
 drivers/accel/qda/Makefile             |   2 +
 drivers/accel/qda/qda_drv.c            |  23 +++-
 drivers/accel/qda/qda_drv.h            |   7 ++
 drivers/accel/qda/qda_gem.c            | 187 +++++++++++++++++++++++++++++++
 drivers/accel/qda/qda_gem.h            |  63 +++++++++++
 drivers/accel/qda/qda_memory_dma.c     |  91 ++++++++++++++++
 drivers/accel/qda/qda_memory_dma.h     |  46 ++++++++
 drivers/accel/qda/qda_memory_manager.c | 194 +++++++++++++++++++++++++++++++++
 drivers/accel/qda/qda_memory_manager.h |  33 ++++++
 9 files changed, 645 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/qda/Makefile b/drivers/accel/qda/Makefile
index f547398e1a72..88c324fa382c 100644
--- a/drivers/accel/qda/Makefile
+++ b/drivers/accel/qda/Makefile
@@ -11,5 +11,7 @@ qda-y := \
 	qda_cb.o \
 	qda_memory_manager.o \
 	qda_ioctl.o \
+	qda_gem.o \
+	qda_memory_dma.o \
 
 obj-$(CONFIG_DRM_ACCEL_QDA_COMPUTE_BUS) += qda_compute_bus.o
diff --git a/drivers/accel/qda/qda_drv.c b/drivers/accel/qda/qda_drv.c
index 86758a9cd982..19798359b14e 100644
--- a/drivers/accel/qda/qda_drv.c
+++ b/drivers/accel/qda/qda_drv.c
@@ -15,7 +15,7 @@
 #include "qda_ioctl.h"
 #include "qda_rpmsg.h"
 
-static struct qda_drm_priv *get_drm_priv_from_device(struct drm_device *dev)
+struct qda_drm_priv *get_drm_priv_from_device(struct drm_device *dev)
 {
 	if (!dev)
 		return NULL;
@@ -88,6 +88,7 @@ static int qda_open(struct drm_device *dev, struct drm_file *file)
 		return -ENOMEM;
 
 	qda_file_priv->pid = current->pid;
+	qda_file_priv->assigned_iommu_dev = NULL; /* Will be assigned on first allocation */
 
 	qda_user = alloc_qda_user(qdev);
 	if (!qda_user) {
@@ -118,6 +119,26 @@ static void qda_postclose(struct drm_device *dev, struct drm_file *file)
 
 	qda_file_priv = (struct qda_file_priv *)file->driver_priv;
 	if (qda_file_priv) {
+		if (qda_file_priv->assigned_iommu_dev) {
+			struct qda_iommu_device *iommu_dev = qda_file_priv->assigned_iommu_dev;
+			unsigned long flags;
+
+			/* Decrement reference count - if it reaches 0, reset PID assignment */
+			if (refcount_dec_and_test(&iommu_dev->refcount)) {
+				/* Last reference released - reset PID assignment */
+				spin_lock_irqsave(&iommu_dev->lock, flags);
+				iommu_dev->assigned_pid = 0;
+				iommu_dev->assigned_file_priv = NULL;
+				spin_unlock_irqrestore(&iommu_dev->lock, flags);
+
+				qda_dbg(qdev, "Reset PID assignment for IOMMU device %u (process %d exited)\n",
+					iommu_dev->id, qda_file_priv->pid);
+			} else {
+				qda_dbg(qdev, "Decremented reference for IOMMU device %u from process %d\n",
+					iommu_dev->id, qda_file_priv->pid);
+			}
+		}
+
 		qda_user = qda_file_priv->qda_user;
 		if (qda_user)
 			free_qda_user(qda_user);
diff --git a/drivers/accel/qda/qda_drv.h b/drivers/accel/qda/qda_drv.h
index e0ba37702a86..8a2cd474958b 100644
--- a/drivers/accel/qda/qda_drv.h
+++ b/drivers/accel/qda/qda_drv.h
@@ -33,6 +33,8 @@ struct qda_file_priv {
 	pid_t pid;
 	/* Pointer to qda_user structure for backward compatibility */
 	struct qda_user *qda_user;
+	/* IOMMU device assigned to this process */
+	struct qda_iommu_device *assigned_iommu_dev;
 };
 
 /**
@@ -153,4 +155,9 @@ void qda_deinit_device(struct qda_dev *qdev);
 int qda_register_device(struct qda_dev *qdev);
 void qda_unregister_device(struct qda_dev *qdev);
 
+/*
+ * Utility function to get DRM private data from DRM device
+ */
+struct qda_drm_priv *get_drm_priv_from_device(struct drm_device *dev);
+
 #endif /* __QDA_DRV_H__ */
diff --git a/drivers/accel/qda/qda_gem.c b/drivers/accel/qda/qda_gem.c
new file mode 100644
index 000000000000..bbd54e2502d3
--- /dev/null
+++ b/drivers/accel/qda/qda_gem.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+#include <drm/drm_gem.h>
+#include <drm/drm_prime.h>
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+#include "qda_drv.h"
+#include "qda_gem.h"
+#include "qda_memory_manager.h"
+#include "qda_memory_dma.h"
+
+static int validate_gem_obj_for_mmap(struct qda_gem_obj *qda_gem_obj)
+{
+	if (qda_gem_obj->size == 0) {
+		qda_err(NULL, "Invalid GEM object size\n");
+		return -EINVAL;
+	}
+	if (!qda_gem_obj->iommu_dev || !qda_gem_obj->iommu_dev->dev) {
+		qda_err(NULL, "Allocated buffer missing IOMMU device\n");
+		return -EINVAL;
+	}
+	if (!qda_gem_obj->iommu_dev->dev) {
+		qda_err(NULL, "Allocated buffer missing IOMMU device\n");
+		return -EINVAL;
+	}
+	if (!qda_gem_obj->virt) {
+		qda_err(NULL, "Allocated buffer missing virtual address\n");
+		return -EINVAL;
+	}
+	if (qda_gem_obj->dma_addr == 0) {
+		qda_err(NULL, "Allocated buffer missing DMA address\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int validate_vma_offset(struct drm_gem_object *drm_obj, struct vm_area_struct *vma)
+{
+	u64 expected_offset = drm_vma_node_offset_addr(&drm_obj->vma_node);
+	u64 actual_offset = vma->vm_pgoff << PAGE_SHIFT;
+
+	if (actual_offset != expected_offset) {
+		qda_err(NULL, "VMA offset mismatch: expected=0x%llx, actual=0x%llx\n",
+			expected_offset, actual_offset);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void setup_vma_flags(struct vm_area_struct *vma)
+{
+	vm_flags_set(vma, VM_DONTEXPAND);
+	vm_flags_set(vma, VM_DONTDUMP);
+}
+
+void qda_gem_free_object(struct drm_gem_object *gem_obj)
+{
+	struct qda_gem_obj *qda_gem_obj = to_qda_gem_obj(gem_obj);
+	struct qda_drm_priv *drm_priv = get_drm_priv_from_device(gem_obj->dev);
+
+	if (qda_gem_obj->virt) {
+		if (drm_priv && drm_priv->iommu_mgr)
+			qda_memory_manager_free(drm_priv->iommu_mgr, qda_gem_obj);
+	}
+
+	drm_gem_object_release(gem_obj);
+	kfree(qda_gem_obj);
+}
+
+int qda_gem_mmap_obj(struct drm_gem_object *drm_obj, struct vm_area_struct *vma)
+{
+	struct qda_gem_obj *qda_gem_obj = to_qda_gem_obj(drm_obj);
+	int ret;
+
+	ret = validate_gem_obj_for_mmap(qda_gem_obj);
+	if (ret) {
+		qda_err(NULL, "GEM object validation failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = validate_vma_offset(drm_obj, vma);
+	if (ret) {
+		qda_err(NULL, "VMA offset validation failed: %d\n", ret);
+		return ret;
+	}
+
+	/* Reset vm_pgoff for DMA mmap */
+	vma->vm_pgoff = 0;
+
+	ret = qda_dma_mmap(qda_gem_obj, vma);
+
+	if (ret == 0) {
+		setup_vma_flags(vma);
+		qda_dbg(NULL, "GEM object mapped successfully\n");
+	} else {
+		qda_err(NULL, "GEM object mmap failed: %d\n", ret);
+	}
+
+	return ret;
+}
+
+static const struct drm_gem_object_funcs qda_gem_object_funcs = {
+	.free = qda_gem_free_object,
+	.mmap = qda_gem_mmap_obj,
+};
+
+struct qda_gem_obj *qda_gem_alloc_object(struct drm_device *drm_dev, size_t aligned_size)
+{
+	struct qda_gem_obj *qda_gem_obj;
+	int ret;
+
+	qda_gem_obj = kzalloc_obj(*qda_gem_obj, GFP_KERNEL);
+	if (!qda_gem_obj)
+		return ERR_PTR(-ENOMEM);
+
+	ret = drm_gem_object_init(drm_dev, &qda_gem_obj->base, aligned_size);
+	if (ret) {
+		qda_err(NULL, "Failed to initialize GEM object: %d\n", ret);
+		kfree(qda_gem_obj);
+		return ERR_PTR(ret);
+	}
+
+	qda_gem_obj->base.funcs = &qda_gem_object_funcs;
+	qda_gem_obj->size = aligned_size;
+
+	qda_dbg(NULL, "Allocated GEM object size=%zu\n", aligned_size);
+	return qda_gem_obj;
+}
+
+void qda_gem_cleanup_object(struct qda_gem_obj *qda_gem_obj)
+{
+	drm_gem_object_release(&qda_gem_obj->base);
+	kfree(qda_gem_obj);
+}
+
+struct drm_gem_object *qda_gem_lookup_object(struct drm_file *file_priv, u32 handle)
+{
+	struct drm_gem_object *gem_obj;
+
+	gem_obj = drm_gem_object_lookup(file_priv, handle);
+	if (!gem_obj)
+		return ERR_PTR(-ENOENT);
+
+	return gem_obj;
+}
+
+int qda_gem_create_handle(struct drm_file *file_priv, struct drm_gem_object *gem_obj, u32 *handle)
+{
+	int ret;
+
+	ret = drm_gem_handle_create(file_priv, gem_obj, handle);
+	drm_gem_object_put(gem_obj);
+
+	return ret;
+}
+
+struct drm_gem_object *qda_gem_create_object(struct drm_device *drm_dev,
+					     struct qda_memory_manager *iommu_mgr, size_t size,
+					     struct drm_file *file_priv)
+{
+	struct qda_gem_obj *qda_gem_obj;
+	size_t aligned_size;
+	int ret;
+
+	if (size == 0) {
+		qda_err(NULL, "Invalid size for GEM object creation\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	aligned_size = PAGE_ALIGN(size);
+
+	qda_gem_obj = qda_gem_alloc_object(drm_dev, aligned_size);
+	if (IS_ERR(qda_gem_obj))
+		return (struct drm_gem_object *)qda_gem_obj;
+
+	ret = qda_memory_manager_alloc(iommu_mgr, qda_gem_obj, file_priv);
+	if (ret) {
+		qda_err(NULL, "Memory manager allocation failed: %d\n", ret);
+		qda_gem_cleanup_object(qda_gem_obj);
+		return ERR_PTR(ret);
+	}
+
+	qda_dbg(NULL, "GEM object created successfully size=%zu\n", aligned_size);
+	return &qda_gem_obj->base;
+}
diff --git a/drivers/accel/qda/qda_gem.h b/drivers/accel/qda/qda_gem.h
new file mode 100644
index 000000000000..caae9cda5363
--- /dev/null
+++ b/drivers/accel/qda/qda_gem.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+#ifndef _QDA_GEM_H
+#define _QDA_GEM_H
+
+#include <linux/xarray.h>
+#include <drm/drm_device.h>
+#include <drm/drm_gem.h>
+#include <linux/dma-mapping.h>
+
+/* Forward declarations */
+struct qda_memory_manager;
+struct qda_iommu_device;
+
+/**
+ * struct qda_gem_obj - QDA GEM buffer object
+ *
+ * This structure represents a GEM buffer object that can be either
+ * allocated by the driver or imported from another driver via dma-buf.
+ */
+struct qda_gem_obj {
+	/* DRM GEM object base structure */
+	struct drm_gem_object base;
+	/* Kernel virtual address of allocated memory */
+	void *virt;
+	/* DMA address for allocated buffers */
+	dma_addr_t dma_addr;
+	/* Size of the buffer in bytes */
+	size_t size;
+	/* IOMMU device that performed the allocation */
+	struct qda_iommu_device *iommu_dev;
+};
+
+/*
+ * Helper macro to cast a drm_gem_object to qda_gem_obj
+ */
+#define to_qda_gem_obj(gem_obj) container_of(gem_obj, struct qda_gem_obj, base)
+
+/*
+ * GEM object lifecycle management
+ */
+struct drm_gem_object *qda_gem_create_object(struct drm_device *drm_dev,
+					     struct qda_memory_manager *iommu_mgr,
+					     size_t size, struct drm_file *file_priv);
+void qda_gem_free_object(struct drm_gem_object *gem_obj);
+int qda_gem_mmap_obj(struct drm_gem_object *gem_obj, struct vm_area_struct *vma);
+
+/*
+ * Helper functions for GEM object allocation and cleanup
+ * These are used internally and by the PRIME import code
+ */
+struct qda_gem_obj *qda_gem_alloc_object(struct drm_device *drm_dev, size_t aligned_size);
+void qda_gem_cleanup_object(struct qda_gem_obj *qda_gem_obj);
+
+/*
+ * Utility functions for GEM operations
+ */
+struct drm_gem_object *qda_gem_lookup_object(struct drm_file *file_priv, u32 handle);
+int qda_gem_create_handle(struct drm_file *file_priv, struct drm_gem_object *gem_obj, u32 *handle);
+
+#endif /* _QDA_GEM_H */
diff --git a/drivers/accel/qda/qda_memory_dma.c b/drivers/accel/qda/qda_memory_dma.c
new file mode 100644
index 000000000000..ffdd5423c88c
--- /dev/null
+++ b/drivers/accel/qda/qda_memory_dma.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+#include "qda_drv.h"
+#include "qda_memory_dma.h"
+
+static dma_addr_t get_actual_dma_addr(struct qda_gem_obj *gem_obj)
+{
+	return gem_obj->dma_addr - ((u64)gem_obj->iommu_dev->sid << 32);
+}
+
+static void setup_gem_object(struct qda_gem_obj *gem_obj, void *virt,
+			     dma_addr_t dma_addr, struct qda_iommu_device *iommu_dev)
+{
+	gem_obj->virt = virt;
+	gem_obj->dma_addr = dma_addr;
+	gem_obj->iommu_dev = iommu_dev;
+}
+
+static void cleanup_gem_object_fields(struct qda_gem_obj *gem_obj)
+{
+	gem_obj->virt = NULL;
+	gem_obj->dma_addr = 0;
+	gem_obj->iommu_dev = NULL;
+}
+
+int qda_dma_alloc(struct qda_iommu_device *iommu_dev,
+		  struct qda_gem_obj *gem_obj, size_t size)
+{
+	void *virt;
+	dma_addr_t dma_addr;
+
+	if (!iommu_dev || !iommu_dev->dev) {
+		qda_err(NULL, "Invalid iommu_dev or device for DMA allocation\n");
+		return -EINVAL;
+	}
+
+	virt = dma_alloc_coherent(iommu_dev->dev, size, &dma_addr, GFP_KERNEL);
+	if (!virt)
+		return -ENOMEM;
+
+	dma_addr += ((u64)iommu_dev->sid << 32);
+
+	qda_dbg(NULL, "DMA address with SID prefix: 0x%llx (sid=%u)\n",
+		(u64)dma_addr, iommu_dev->sid);
+
+	setup_gem_object(gem_obj, virt, dma_addr, iommu_dev);
+
+	return 0;
+}
+
+void qda_dma_free(struct qda_gem_obj *gem_obj)
+{
+	if (!gem_obj || !gem_obj->iommu_dev) {
+		qda_dbg(NULL, "Invalid gem_obj or iommu_dev for DMA free\n");
+		return;
+	}
+
+	qda_dbg(NULL, "DMA freeing: size=%zu, device_id=%u, dma_addr=0x%llx\n",
+		gem_obj->size, gem_obj->iommu_dev->id, gem_obj->dma_addr);
+
+	dma_free_coherent(gem_obj->iommu_dev->dev, gem_obj->size,
+			  gem_obj->virt, get_actual_dma_addr(gem_obj));
+
+	cleanup_gem_object_fields(gem_obj);
+}
+
+int qda_dma_mmap(struct qda_gem_obj *gem_obj, struct vm_area_struct *vma)
+{
+	struct qda_iommu_device *iommu_dev;
+	int ret;
+
+	if (!gem_obj || !gem_obj->virt || !gem_obj->iommu_dev || !gem_obj->iommu_dev->dev) {
+		qda_err(NULL, "Invalid parameters for DMA mmap\n");
+		return -EINVAL;
+	}
+
+	iommu_dev = gem_obj->iommu_dev;
+
+	ret = dma_mmap_coherent(iommu_dev->dev, vma, gem_obj->virt,
+				get_actual_dma_addr(gem_obj), gem_obj->size);
+
+	if (ret)
+		qda_err(NULL, "DMA mmap failed: size=%zu, device_id=%u, ret=%d\n",
+			gem_obj->size, iommu_dev->id, ret);
+	else
+		qda_dbg(NULL, "DMA mmap successful: size=%zu\n", gem_obj->size);
+
+	return ret;
+}
diff --git a/drivers/accel/qda/qda_memory_dma.h b/drivers/accel/qda/qda_memory_dma.h
new file mode 100644
index 000000000000..79b3c4053a82
--- /dev/null
+++ b/drivers/accel/qda/qda_memory_dma.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#ifndef _QDA_MEMORY_DMA_H
+#define _QDA_MEMORY_DMA_H
+
+#include <linux/dma-mapping.h>
+#include "qda_memory_manager.h"
+
+/**
+ * qda_dma_alloc() - Allocate DMA coherent memory for a GEM object
+ * @iommu_dev: Pointer to the QDA IOMMU device structure
+ * @gem_obj: Pointer to GEM object to allocate memory for
+ * @size: Size of memory to allocate in bytes
+ *
+ * Allocates DMA-coherent memory and sets up the GEM object with the
+ * allocated memory details including virtual and DMA addresses.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int qda_dma_alloc(struct qda_iommu_device *iommu_dev,
+		  struct qda_gem_obj *gem_obj, size_t size);
+
+/**
+ * qda_dma_free() - Free DMA coherent memory for a GEM object
+ * @gem_obj: Pointer to GEM object to free memory for
+ *
+ * Frees DMA-coherent memory previously allocated for the GEM object
+ * and cleans up the GEM object fields.
+ */
+void qda_dma_free(struct qda_gem_obj *gem_obj);
+
+/**
+ * qda_dma_mmap() - Map DMA memory into userspace
+ * @gem_obj: Pointer to GEM object containing DMA memory
+ * @vma: Virtual memory area to map into
+ *
+ * Maps DMA-coherent memory into userspace virtual address space.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int qda_dma_mmap(struct qda_gem_obj *gem_obj, struct vm_area_struct *vma);
+
+#endif /* _QDA_MEMORY_DMA_H */
diff --git a/drivers/accel/qda/qda_memory_manager.c b/drivers/accel/qda/qda_memory_manager.c
index b4c7047a89d4..e225667557ee 100644
--- a/drivers/accel/qda/qda_memory_manager.c
+++ b/drivers/accel/qda/qda_memory_manager.c
@@ -6,8 +6,11 @@
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <linux/xarray.h>
+#include <drm/drm_file.h>
 #include "qda_drv.h"
+#include "qda_gem.h"
 #include "qda_memory_manager.h"
+#include "qda_memory_dma.h"
 
 static void cleanup_all_memory_devices(struct qda_memory_manager *mem_mgr)
 {
@@ -55,6 +58,8 @@ static void init_iommu_device_fields(struct qda_iommu_device *iommu_dev,
 	spin_lock_init(&iommu_dev->lock);
 	refcount_set(&iommu_dev->refcount, 0);
 	INIT_WORK(&iommu_dev->remove_work, qda_memory_manager_remove_work);
+	iommu_dev->assigned_pid = 0;
+	iommu_dev->assigned_file_priv = NULL;
 }
 
 static int allocate_device_id(struct qda_memory_manager *mem_mgr,
@@ -78,6 +83,194 @@ static int allocate_device_id(struct qda_memory_manager *mem_mgr,
 	return ret;
 }
 
+static struct qda_iommu_device *find_device_for_pid(struct qda_memory_manager *mem_mgr,
+						    pid_t pid)
+{
+	unsigned long index;
+	void *entry;
+	struct qda_iommu_device *found_dev = NULL;
+	unsigned long flags;
+
+	xa_lock(&mem_mgr->device_xa);
+	xa_for_each(&mem_mgr->device_xa, index, entry) {
+		struct qda_iommu_device *iommu_dev = entry;
+
+		spin_lock_irqsave(&iommu_dev->lock, flags);
+		if (iommu_dev->assigned_pid == pid) {
+			found_dev = iommu_dev;
+			refcount_inc(&found_dev->refcount);
+			qda_dbg(NULL, "Reusing device id=%u for PID=%d (refcount=%u)\n",
+				found_dev->id, pid, refcount_read(&found_dev->refcount));
+			spin_unlock_irqrestore(&iommu_dev->lock, flags);
+			break;
+		}
+		spin_unlock_irqrestore(&iommu_dev->lock, flags);
+	}
+	xa_unlock(&mem_mgr->device_xa);
+
+	return found_dev;
+}
+
+static struct qda_iommu_device *assign_available_device_to_pid(struct qda_memory_manager *mem_mgr,
+							       pid_t pid,
+							       struct drm_file *file_priv)
+{
+	unsigned long index;
+	void *entry;
+	struct qda_iommu_device *selected_dev = NULL;
+	unsigned long flags;
+
+	xa_lock(&mem_mgr->device_xa);
+	xa_for_each(&mem_mgr->device_xa, index, entry) {
+		struct qda_iommu_device *iommu_dev = entry;
+
+		spin_lock_irqsave(&iommu_dev->lock, flags);
+		if (iommu_dev->assigned_pid == 0) {
+			iommu_dev->assigned_pid = pid;
+			iommu_dev->assigned_file_priv = file_priv;
+			selected_dev = iommu_dev;
+			refcount_set(&selected_dev->refcount, 1);
+			qda_dbg(NULL, "Assigned device id=%u to PID=%d\n",
+				selected_dev->id, pid);
+			spin_unlock_irqrestore(&iommu_dev->lock, flags);
+			break;
+		}
+		spin_unlock_irqrestore(&iommu_dev->lock, flags);
+	}
+	xa_unlock(&mem_mgr->device_xa);
+
+	return selected_dev;
+}
+
+static struct qda_iommu_device *get_process_iommu_device(struct qda_memory_manager *mem_mgr,
+							 struct drm_file *file_priv)
+{
+	struct qda_file_priv *qda_priv;
+
+	if (!file_priv || !file_priv->driver_priv)
+		return NULL;
+
+	qda_priv = (struct qda_file_priv *)file_priv->driver_priv;
+	return qda_priv->assigned_iommu_dev;
+}
+
+static int qda_memory_manager_assign_device(struct qda_memory_manager *mem_mgr,
+					    struct drm_file *file_priv)
+{
+	struct qda_file_priv *qda_priv;
+	struct qda_iommu_device *selected_dev = NULL;
+	int ret = 0;
+	pid_t current_pid;
+
+	if (!file_priv || !file_priv->driver_priv) {
+		qda_err(NULL, "Invalid file_priv or driver_priv\n");
+		return -EINVAL;
+	}
+
+	qda_priv = (struct qda_file_priv *)file_priv->driver_priv;
+	current_pid = qda_priv->pid;
+
+	mutex_lock(&mem_mgr->process_assignment_lock);
+
+	if (qda_priv->assigned_iommu_dev) {
+		qda_dbg(NULL, "PID=%d already has device id=%u assigned\n",
+			current_pid, qda_priv->assigned_iommu_dev->id);
+		ret = 0;
+		goto unlock_and_return;
+	}
+
+	selected_dev = find_device_for_pid(mem_mgr, current_pid);
+
+	if (selected_dev) {
+		qda_priv->assigned_iommu_dev = selected_dev;
+		goto unlock_and_return;
+	}
+
+	selected_dev = assign_available_device_to_pid(mem_mgr, current_pid, file_priv);
+
+	if (!selected_dev) {
+		qda_err(NULL, "No available device for PID=%d\n", current_pid);
+		ret = -ENOMEM;
+		goto unlock_and_return;
+	}
+
+	qda_priv->assigned_iommu_dev = selected_dev;
+
+unlock_and_return:
+	mutex_unlock(&mem_mgr->process_assignment_lock);
+	return ret;
+}
+
+static struct qda_iommu_device *get_or_assign_iommu_device(struct qda_memory_manager *mem_mgr,
+							   struct drm_file *file_priv,
+							   size_t size)
+{
+	struct qda_iommu_device *iommu_dev;
+	int ret;
+
+	iommu_dev = get_process_iommu_device(mem_mgr, file_priv);
+	if (iommu_dev)
+		return iommu_dev;
+
+	ret = qda_memory_manager_assign_device(mem_mgr, file_priv);
+	if (ret)
+		return NULL;
+
+	iommu_dev = get_process_iommu_device(mem_mgr, file_priv);
+	if (iommu_dev)
+		return iommu_dev;
+
+	return NULL;
+}
+
+int qda_memory_manager_alloc(struct qda_memory_manager *mem_mgr, struct qda_gem_obj *gem_obj,
+			     struct drm_file *file_priv)
+{
+	struct qda_iommu_device *selected_dev;
+	size_t size;
+	int ret;
+
+	if (!mem_mgr || !gem_obj || !file_priv) {
+		qda_err(NULL, "Invalid parameters for memory allocation\n");
+		return -EINVAL;
+	}
+
+	size = gem_obj->size;
+	if (size == 0) {
+		qda_err(NULL, "Invalid allocation size: 0\n");
+		return -EINVAL;
+	}
+
+	selected_dev = get_or_assign_iommu_device(mem_mgr, file_priv, size);
+
+	if (!selected_dev) {
+		qda_err(NULL, "Failed to get/assign device for allocation (size=%zu)\n", size);
+		return -ENOMEM;
+	}
+
+	ret = qda_dma_alloc(selected_dev, gem_obj, size);
+
+	if (ret) {
+		qda_err(NULL, "Allocation failed: size=%zu, device_id=%u, ret=%d\n",
+			size, selected_dev->id, ret);
+		return ret;
+	}
+
+	qda_dbg(NULL, "Successfully allocated: size=%zu, device_id=%u, dma_addr=0x%llx\n",
+		size, selected_dev->id, gem_obj->dma_addr);
+	return 0;
+}
+
+void qda_memory_manager_free(struct qda_memory_manager *mem_mgr, struct qda_gem_obj *gem_obj)
+{
+	if (!gem_obj || !gem_obj->iommu_dev) {
+		qda_dbg(NULL, "Invalid gem_obj or iommu_dev for free\n");
+		return;
+	}
+
+	qda_dma_free(gem_obj);
+}
+
 int qda_memory_manager_register_device(struct qda_memory_manager *mem_mgr,
 				       struct qda_iommu_device *iommu_dev)
 {
@@ -134,6 +327,7 @@ int qda_memory_manager_init(struct qda_memory_manager *mem_mgr)
 
 	xa_init_flags(&mem_mgr->device_xa, XA_FLAGS_ALLOC);
 	atomic_set(&mem_mgr->next_id, 0);
+	mutex_init(&mem_mgr->process_assignment_lock);
 	mem_mgr->wq = create_workqueue("memory_manager_wq");
 	if (!mem_mgr->wq) {
 		qda_err(NULL, "Failed to create memory manager workqueue\n");
diff --git a/drivers/accel/qda/qda_memory_manager.h b/drivers/accel/qda/qda_memory_manager.h
index 3bf4cd529909..bac44284ef98 100644
--- a/drivers/accel/qda/qda_memory_manager.h
+++ b/drivers/accel/qda/qda_memory_manager.h
@@ -11,6 +11,8 @@
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <linux/xarray.h>
+#include <drm/drm_file.h>
+#include "qda_gem.h"
 
 /**
  * struct qda_iommu_device - IOMMU device instance for memory management
@@ -35,6 +37,10 @@ struct qda_iommu_device {
 	u32 sid;
 	/* Pointer to parent memory manager */
 	struct qda_memory_manager *manager;
+	/* Process ID of the process assigned to this device */
+	pid_t assigned_pid;
+	/* DRM file private data for the assigned process */
+	struct drm_file *assigned_file_priv;
 };
 
 /**
@@ -51,6 +57,8 @@ struct qda_memory_manager {
 	atomic_t next_id;
 	/* Workqueue for asynchronous device operations */
 	struct workqueue_struct *wq;
+	/* Mutex protecting process-to-device assignments */
+	struct mutex process_assignment_lock;
 };
 
 /**
@@ -98,4 +106,29 @@ int qda_memory_manager_register_device(struct qda_memory_manager *mem_mgr,
 void qda_memory_manager_unregister_device(struct qda_memory_manager *mem_mgr,
 					  struct qda_iommu_device *iommu_dev);
 
+/**
+ * qda_memory_manager_alloc() - Allocate memory for a GEM object
+ * @mem_mgr: Pointer to memory manager
+ * @gem_obj: Pointer to GEM object to allocate memory for
+ * @file_priv: DRM file private data for process association
+ *
+ * Allocates memory for the specified GEM object using an appropriate IOMMU
+ * device. The allocation is associated with the calling process via
+ * file_priv.
+ *
+ * Return: 0 on success, negative error code on failure
+ */
+int qda_memory_manager_alloc(struct qda_memory_manager *mem_mgr, struct qda_gem_obj *gem_obj,
+			     struct drm_file *file_priv);
+
+/**
+ * qda_memory_manager_free() - Free memory for a GEM object
+ * @mem_mgr: Pointer to memory manager
+ * @gem_obj: Pointer to GEM object to free memory for
+ *
+ * Releases memory previously allocated for the specified GEM object and
+ * removes any associated IOMMU mappings.
+ */
+void qda_memory_manager_free(struct qda_memory_manager *mem_mgr, struct qda_gem_obj *gem_obj);
+
 #endif /* _QDA_MEMORY_MANAGER_H */

-- 
2.34.1