SWD Debug Interface

These pages are organized into two layers:

• SWD Base Class: describes the LibXR::Debug::Swd abstraction, transfer policy, and DP/AP helper APIs
• SWD GPIO Implementation: describes the GPIO bit-bang SwdGeneralGPIO implementation, plus loops_per_us calibration and frequency selection

In current mainline, these two layers map directly to the real source layering:

• the Swd base class owns link control, the single-transfer Transfer() primitive, the WAIT-retry wrapper, and DP/AP helper APIs;
• SwdGeneralGPIO is one concrete backend that implements that abstraction over GPIO bit-banging.