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UIO DMA Driver for Ara240 DNPU

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Linux kernel driver providing userspace I/O (UIO) access to DMA-capable memory regions.

Overview

The UIO DMA driver is an out-of-tree Linux kernel module that enables userspace applications to allocate and manage DMA (Direct Memory Access) buffers through the UIO (Userspace I/O) framework. This allows zero-copy data transfers between hardware devices and userspace applications.

DMA Buffer Management for NPU

The UIO DMA driver enables:

  • Zero-copy data transfer to the Ara240 NPU
  • Efficient input tensor allocation
  • Direct memory access for inference results
  • Reduced latency for AI/ML pipelines

Architecture

This repository contains two versions of the driver:

1. uiodma/ - Standard x86 Version

  • Platform: x86/x86_64 architectures
  • Cache Model: Cache-coherent systems
  • Use Case: Standard PC/server platforms with hardware cache coherency

2️. uiodma_cache_management/ - NXP i.MX Version

  • Platform: ARM-based NXP i.MX SoCs (i.MX 8M Plus, i.MX 95, etc.)
  • Cache Model: Implements explicit cache management operations
  • Use Case: Embedded ARM platforms requiring manual cache synchronization

Features:

  • Manual cache flush/invalidate operations
  • Proper handling of non-coherent DMA
  • Optimized for ARM memory subsystems

💡 Important: Always use uiodma_cache_management/ for NXP i.MX devices to ensure data coherency between the CPU and DMA operations.

Prerequisites

Build Requirements

  • Linux kernel headers matching your running kernel
  • GCC compiler
  • Make build system
  • Root/sudo privileges for module installation

Install kernel headers (example for Debian/Ubuntu-based systems):

sudo apt-get update
sudo apt-get install linux-headers-$(uname -r)

For NXP i.MX Yocto builds:

Ensure kernel headers are available in your BSP. The kernel version must match your target device (e.g., 6.18.20-2.0.0 for recent i.MX releases).

Build Instructions

For x86 Platforms

cd uiodma/
make clean
make

For NXP i.MX Platforms (ARM)

Cross-compilation on host PC

source <toolchain-path>/environment-setup-armv8-2a-poky-linux
cd uiodma_cache_management/
make clean
make KERNEL_SRC=<path-to-kernel-source>

Note: The kernel specified by KERNEL_SRC must be built beforehand.

Installation

For x86 Platforms

Load the module manually:

sudo insmod uiodma/uiodma.ko

For NXP i.MX Platforms (Runtime SDK Integration)

⚠️ Critical: SDK Integration Path

When using uiodma with rt-sdk-ara2 (Ara240 Runtime SDK) on i.MX devices, the module must be placed at:

/usr/share/rt-sdk-ara240/driver/uiodma.ko

Step 1: Deploy to SDK path

scp uiodma_cache_management/uiodma.ko root@<i.mx_ip_addr>:/usr/share/rt-sdk-ara240/driver/

Note: Modifying this path will require an update to the Ara240 SDK configuration.

⚖️ License

This driver is licensed under GPL-2.0-only.

Note: This is an out-of-tree kernel module. It is not part of the mainline Linux kernel and must be maintained separately for each kernel version.