Talk:Used IP cores

A20 GIC Documentation Anomaly

I was probing on one of my A20 devices, and found a documentation anomaly:

A20 User Manual: GIC Registers 0x01C8 0000---0x01C8 7FFF (32k) "For details about GIC, please refer to the GIC PL400 technical reference manual and ARM GIC Architecture Specification V2.0." (I added the link, it wasn't in the User Manual)

ARM Doesn't make a device or IP Core called the GIC PL400, but they do make a device called the "CoreLink™ GIC-400 Generic Interrupt Controller". I read into that document.

I peeked at the address associated with the Distributor Implementer Identification Register, GICD_IIDR. in the GIC-400 TRM, the value is fixed at 0x0200143B.

# devmem2 0x01c81008
Value at address 0x01C81008: 0x0100143B

This isn't the value found in ARM DDI 0471B: CoreLink™ GIC-400 Generic Interrupt Controller Revision: r0p1 Technical Reference Manual.

I found this documented in ARM DDI 0464F: Cortex™-A7 MPCore™ Revision: r0p5 Technical Reference Manual.

The value corresponds to the GIC in the Cortex-A7, not the separate GIC-400. The reference to the GIC-400 in the A20 User Manual is actually incorrect. Likewise, the indication on this page is incorrect as a result.