accel/rocket: Add IOCTL for BO creation

This uses the SHMEM DRM helpers and we map right away to the CPU and NPU
sides, as all buffers are expected to be accessed from both.

v2:
- Sync the IOMMUs for the other cores when mapping and unmapping.

v3:
- Make use of GPL-2.0-only for the copyright notice (Jeff Hugo)

v6:
- Use mutexes guard (Markus Elfring)

v7:
- Assign its own IOMMU domain to each client, for isolation (Daniel
  Stone and Robin Murphy)

v8:
- Correctly acquire a reference to the IOMMU (Robin Murphy)
- Allocate DMA address ourselves with drm_mm (Robin Murphy)
- Use refcount_read (Heiko Stuebner)
- Remove superfluous dma_sync_sgtable_for_device (Robin Murphy)

Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Tomeu Vizoso <tomeu@tomeuvizoso.net>
Signed-off-by: Jeff Hugo <jeff.hugo@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250721-6-10-rocket-v9-3-77ebd484941e@tomeuvizoso.net

drivers/accel/rocket/Makefile

@@ -5,4 +5,5 @@ obj-$(CONFIG_DRM_ACCEL_ROCKET) := rocket.o
 rocket-y := \
 	rocket_core.o \
 	rocket_device.o \
-	rocket_drv.o
+	rocket_drv.o \
+	rocket_gem.o

drivers/accel/rocket/rocket_drv.c

@@ -5,6 +5,7 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_ioctl.h>
+#include <drm/rocket_accel.h>
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/iommu.h>
@@ -13,6 +14,7 @@
 #include <linux/pm_runtime.h>
 
 #include "rocket_drv.h"
+#include "rocket_gem.h"
 
 /*
  * Facade device, used to expose a single DRM device to userspace, that
@@ -69,6 +71,7 @@ rocket_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct rocket_device *rdev = to_rocket_device(dev);
 	struct rocket_file_priv *rocket_priv;
+	u64 start, end;
 	int ret;
 
 	if (!try_module_get(THIS_MODULE))
@@ -89,6 +92,11 @@ rocket_open(struct drm_device *dev, struct drm_file *file)
 
 	file->driver_priv = rocket_priv;
 
+	start = rocket_priv->domain->domain->geometry.aperture_start;
+	end = rocket_priv->domain->domain->geometry.aperture_end;
+	drm_mm_init(&rocket_priv->mm, start, end - start + 1);
+	mutex_init(&rocket_priv->mm_lock);
+
 	return 0;
 
 err_free:
@@ -103,6 +111,8 @@ rocket_postclose(struct drm_device *dev, struct drm_file *file)
 {
 	struct rocket_file_priv *rocket_priv = file->driver_priv;
 
+	mutex_destroy(&rocket_priv->mm_lock);
+	drm_mm_takedown(&rocket_priv->mm);
 	rocket_iommu_domain_put(rocket_priv->domain);
 	kfree(rocket_priv);
 	module_put(THIS_MODULE);
@@ -111,6 +121,8 @@ rocket_postclose(struct drm_device *dev, struct drm_file *file)
 static const struct drm_ioctl_desc rocket_drm_driver_ioctls[] = {
 #define ROCKET_IOCTL(n, func) \
 	DRM_IOCTL_DEF_DRV(ROCKET_##n, rocket_ioctl_##func, 0)
+
+	ROCKET_IOCTL(CREATE_BO, create_bo),
 };
 
 DEFINE_DRM_ACCEL_FOPS(rocket_accel_driver_fops);
@@ -120,9 +132,10 @@ DEFINE_DRM_ACCEL_FOPS(rocket_accel_driver_fops);
  * - 1.0 - initial interface
  */
 static const struct drm_driver rocket_drm_driver = {
-	.driver_features	= DRIVER_COMPUTE_ACCEL,
+	.driver_features	= DRIVER_COMPUTE_ACCEL | DRIVER_GEM,
 	.open			= rocket_open,
 	.postclose		= rocket_postclose,
+	.gem_create_object	= rocket_gem_create_object,
 	.ioctls			= rocket_drm_driver_ioctls,
 	.num_ioctls		= ARRAY_SIZE(rocket_drm_driver_ioctls),
 	.fops			= &rocket_accel_driver_fops,

drivers/accel/rocket/rocket_drv.h

@@ -4,6 +4,8 @@
 #ifndef __ROCKET_DRV_H__
 #define __ROCKET_DRV_H__
 
+#include <drm/drm_mm.h>
+
 #include "rocket_device.h"
 
 struct rocket_iommu_domain {
@@ -15,6 +17,8 @@ struct rocket_file_priv {
 	struct rocket_device *rdev;
 
 	struct rocket_iommu_domain *domain;
+	struct drm_mm mm;
+	struct mutex mm_lock;
 };
 
 struct rocket_iommu_domain *rocket_iommu_domain_get(struct rocket_file_priv *rocket_priv);

drivers/accel/rocket/rocket_gem.c

@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright 2024-2025 Tomeu Vizoso <tomeu@tomeuvizoso.net> */
+
+#include <drm/drm_device.h>
+#include <drm/drm_utils.h>
+#include <drm/rocket_accel.h>
+#include <linux/dma-mapping.h>
+#include <linux/iommu.h>
+
+#include "rocket_drv.h"
+#include "rocket_gem.h"
+
+static void rocket_gem_bo_free(struct drm_gem_object *obj)
+{
+	struct rocket_gem_object *bo = to_rocket_bo(obj);
+	struct rocket_file_priv *rocket_priv = bo->driver_priv;
+	size_t unmapped;
+
+	drm_WARN_ON(obj->dev, refcount_read(&bo->base.pages_use_count) > 1);
+
+	unmapped = iommu_unmap(bo->domain->domain, bo->mm.start, bo->size);
+	drm_WARN_ON(obj->dev, unmapped != bo->size);
+
+	mutex_lock(&rocket_priv->mm_lock);
+	drm_mm_remove_node(&bo->mm);
+	mutex_unlock(&rocket_priv->mm_lock);
+
+	rocket_iommu_domain_put(bo->domain);
+	bo->domain = NULL;
+
+	drm_gem_shmem_free(&bo->base);
+}
+
+static const struct drm_gem_object_funcs rocket_gem_funcs = {
+	.free = rocket_gem_bo_free,
+	.print_info = drm_gem_shmem_object_print_info,
+	.pin = drm_gem_shmem_object_pin,
+	.unpin = drm_gem_shmem_object_unpin,
+	.get_sg_table = drm_gem_shmem_object_get_sg_table,
+	.vmap = drm_gem_shmem_object_vmap,
+	.vunmap = drm_gem_shmem_object_vunmap,
+	.mmap = drm_gem_shmem_object_mmap,
+	.vm_ops = &drm_gem_shmem_vm_ops,
+};
+
+struct drm_gem_object *rocket_gem_create_object(struct drm_device *dev, size_t size)
+{
+	struct rocket_gem_object *obj;
+
+	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return ERR_PTR(-ENOMEM);
+
+	obj->base.base.funcs = &rocket_gem_funcs;
+
+	return &obj->base.base;
+}
+
+int rocket_ioctl_create_bo(struct drm_device *dev, void *data, struct drm_file *file)
+{
+	struct rocket_file_priv *rocket_priv = file->driver_priv;
+	struct drm_rocket_create_bo *args = data;
+	struct drm_gem_shmem_object *shmem_obj;
+	struct rocket_gem_object *rkt_obj;
+	struct drm_gem_object *gem_obj;
+	struct sg_table *sgt;
+	int ret;
+
+	shmem_obj = drm_gem_shmem_create(dev, args->size);
+	if (IS_ERR(shmem_obj))
+		return PTR_ERR(shmem_obj);
+
+	gem_obj = &shmem_obj->base;
+	rkt_obj = to_rocket_bo(gem_obj);
+
+	rkt_obj->driver_priv = rocket_priv;
+	rkt_obj->domain = rocket_iommu_domain_get(rocket_priv);
+	rkt_obj->size = args->size;
+	rkt_obj->offset = 0;
+
+	ret = drm_gem_handle_create(file, gem_obj, &args->handle);
+	drm_gem_object_put(gem_obj);
+	if (ret)
+		goto err;
+
+	sgt = drm_gem_shmem_get_pages_sgt(shmem_obj);
+	if (IS_ERR(sgt)) {
+		ret = PTR_ERR(sgt);
+		goto err;
+	}
+
+	mutex_lock(&rocket_priv->mm_lock);
+	ret = drm_mm_insert_node_generic(&rocket_priv->mm, &rkt_obj->mm,
+					 rkt_obj->size, PAGE_SIZE,
+					 0, 0);
+	mutex_unlock(&rocket_priv->mm_lock);
+
+	ret = iommu_map_sgtable(rocket_priv->domain->domain,
+				rkt_obj->mm.start,
+				shmem_obj->sgt,
+				IOMMU_READ | IOMMU_WRITE);
+	if (ret < 0 || ret < args->size) {
+		drm_err(dev, "failed to map buffer: size=%d request_size=%u\n",
+			ret, args->size);
+		ret = -ENOMEM;
+		goto err_remove_node;
+	}
+
+	/* iommu_map_sgtable might have aligned the size */
+	rkt_obj->size = ret;
+	args->offset = drm_vma_node_offset_addr(&gem_obj->vma_node);
+	args->dma_address = rkt_obj->mm.start;
+
+	return 0;
+
+err_remove_node:
+	mutex_lock(&rocket_priv->mm_lock);
+	drm_mm_remove_node(&rkt_obj->mm);
+	mutex_unlock(&rocket_priv->mm_lock);
+
+err:
+	drm_gem_shmem_object_free(gem_obj);
+
+	return ret;
+}

drivers/accel/rocket/rocket_gem.h

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright 2024-2025 Tomeu Vizoso <tomeu@tomeuvizoso.net> */
+
+#ifndef __ROCKET_GEM_H__
+#define __ROCKET_GEM_H__
+
+#include <drm/drm_gem_shmem_helper.h>
+
+struct rocket_gem_object {
+	struct drm_gem_shmem_object base;
+
+	struct rocket_file_priv *driver_priv;
+
+	struct rocket_iommu_domain *domain;
+	struct drm_mm_node mm;
+	size_t size;
+	u32 offset;
+};
+
+struct drm_gem_object *rocket_gem_create_object(struct drm_device *dev, size_t size);
+
+int rocket_ioctl_create_bo(struct drm_device *dev, void *data, struct drm_file *file);
+
+static inline
+struct  rocket_gem_object *to_rocket_bo(struct drm_gem_object *obj)
+{
+	return container_of(to_drm_gem_shmem_obj(obj), struct rocket_gem_object, base);
+}
+
+#endif

include/uapi/drm/rocket_accel.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Tomeu Vizoso
+ */
+#ifndef __DRM_UAPI_ROCKET_ACCEL_H__
+#define __DRM_UAPI_ROCKET_ACCEL_H__
+
+#include "drm.h"
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+#define DRM_ROCKET_CREATE_BO			0x00
+
+#define DRM_IOCTL_ROCKET_CREATE_BO		DRM_IOWR(DRM_COMMAND_BASE + DRM_ROCKET_CREATE_BO, struct drm_rocket_create_bo)
+
+/**
+ * struct drm_rocket_create_bo - ioctl argument for creating Rocket BOs.
+ *
+ */
+struct drm_rocket_create_bo {
+	/** Input: Size of the requested BO. */
+	__u32 size;
+
+	/** Output: GEM handle for the BO. */
+	__u32 handle;
+
+	/**
+	 * Output: DMA address for the BO in the NPU address space.  This address
+	 * is private to the DRM fd and is valid for the lifetime of the GEM
+	 * handle.
+	 */
+	__u64 dma_address;
+
+	/** Output: Offset into the drm node to use for subsequent mmap call. */
+	__u64 offset;
+};
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* __DRM_UAPI_ROCKET_ACCEL_H__ */