Linux 7.4 adds I3C hub framework and HDR-DDR support

The Linux 7.4 kernel includes significant updates to the MIPI I3C subsystem, specifically targeting improved connectivity and data throughput. These changes introduce a new generic framework for I3C hubs, which allows for expanded communication and bridging across connected devices.

In addition to the hub architecture, the kernel now supports High Data Rate Double Data Rate (HDR-DDR) modes. This enhancement is implemented within the mipi-i3c-hci driver, enabling faster data transfers for hardware utilizing the I3C protocol.

Technical improvements in the I3C subsystem

• I3C Hub Framework: A new generic framework has been integrated into the core I3C master code to facilitate hub support and device bridging.
• NXP Driver Support: The merge includes a new driver specifically for the NXP P3H2x4x family of multi-port I3C hub devices.
• HDR-DDR Throughput: The mipi-i3c-hci driver now supports High Data Rate Double Data Rate, utilizing dual edge sampling to reach throughputs of up to 25 Mbps.
• Code Maturity: The hub implementation underwent 20 rounds of code review prior to being merged into the 7.4 mainline kernel.

Why it matters

These updates improve Linux support for modern embedded systems and sensor networks that rely on the MIPI I3C standard. The ability to use hubs and higher data rates allows hardware engineers to design more complex, high-speed communication topologies for mobile and IoT devices running Linux.