Overview of peripheral interfaces

The Qualcomm® Linux® interfaces guide describes both the low-speed and high-speed input/output (I/O) peripheral interface subsystems used in the System-on-Chip (SoC).

• The low-speed I/O interfaces operate at a lower frequency than the high-speed interfaces in the SoC. The Qualcomm universal peripheral (QUP) v3 serial engine is a hardware core that supports the following low-speed peripheral interfaces:
  • Universal asynchronous receiver/transmitter (UART)
  • Serial peripheral interface (SPI)
  • Interintegrated circuit (I2C)
  • Improved interintegrated circuit (I3C)
  These low-speed interfaces communicate with low-speed peripherals, such as sensor interface devices, Bluetooth® wireless technology devices, display or touch interface devices.
• The high-speed I/O interfaces include the following peripheral interfaces:
  • Peripheral component interconnect express (PCIe)
  • Universal serial bus (USB)
  The high-speed I/O interfaces are used to connect to high-speed devices, such as solid-state drives, network cards, external graphics cards.

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Peripheral interfaces software stack

The following figure shows the software stack for peripheral interfaces. Figure : Peripheral interfaces software stack high level (high-level view) Application to QUP GENI hardware (high-level Linux flow) In Linux, applications communicate with peripherals through standard user-space interfaces provided by the kernel, such as /dev nodes or subsystem APIs. The flow works as follows:

1. Application layer
   • An application issues a request using a standard user-space interface.
   • The request enters the kernel through a system call.
2. Kernel core framework
   • The kernel routes the request to the relevant subsystem, such as:
     • I2C
     • SPI
     • I3C
     • TTY
   • The subsystem performs the following functions:
     • Provides protocol-aware abstractions
     • Manages synchronization and concurrency
     • Integrates power-management hooks
     • Offers a uniform programming interface to clients
3. Protocol controller driver
   • The core framework calls the protocol controller driver.
   • The driver translates framework-level operations into hardware-specific commands.
4. QUPv3 GENI Serial Engine (Qualcomm platforms)
   • The controller driver programs the QUPv3 GENI serial engine.
   • GENI implements the selected protocol (I2C, SPI, I3C, or UART) using:
     • Configured transfer modes
     • Protocol firmware
5. GENI hardware execution
   • Performs register-level operations.
   • Moves data between the system and the external device.

Throughout this process, the kernel framework retains control over:

• Driver and device lifecycle management
• Concurrency handling
• Power state coordination across the stack

The following figure shows the Linux flow from application to QUP-GENI hardware. Figure : Peripheral interfaces software stack high level (low-level view)

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QUP v3

Qualcomm uses QUP v3, a highly flexible and programmable hardware to support a wide range of serial interfaces. For more information about QUP v3, see the following resources:

• QUP v3 overview
• Supported transfer modes in QUP v3
• QUP v3 access control customization
• QUP v3 firmware status verification

This guide is your primary resource for information about enabling low-speed and high-speed I/O interfaces and making configuration changes.