US 11,853,251 B2
On-die chip-to-chip (C2C) link state monitor
Ramesh Krishnamurthy Madhira, San Jose, CA (US); Ibrahim Ouda, Austin, TX (US); and Kaushik Roychowdhury, Austin, TX (US)
Assigned to QUALCOMM Incorporated, San Diego, CA (US)
Filed by QUALCOMM Incorporated, San Diego, CA (US)
Filed on May 4, 2022, as Appl. No. 17/662,032.
Prior Publication US 2023/0359579 A1, Nov. 9, 2023
Int. Cl. G06F 13/42 (2006.01); G06F 1/14 (2006.01)
CPC G06F 13/4282 (2013.01) [G06F 1/14 (2013.01); G06F 2213/0026 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A method of on-die monitoring of chip-to-chip (C2C) serial link state, the method comprising:
at an on-die C2C serial link state machine monitoring circuit for monitoring a serial link state machine for communicating via a C2C serial link according to a C2C protocol:
detecting a change of a link state of the C2C serial link from a first link state to a second link state;
storing, in an on-die first-in, first-out (FIFO) buffer, link state change information, the link state change information comprising information indicating the first link state, a duration of time that the C2C serial link was in the first link state, and a speed of the C2C serial link in the first link state, wherein storing information indicating the duration of time the C2C serial link was in the first link state comprises storing information indicating how many clock cycles the C2C serial link was in the first link state;
detecting the duration of time that the speed of C2C serial link in the first state exceeding an overflow condition and setting the information indicating how many clock cycles the C2C serial link was in the first link state to a configurable value;
detecting a request for link state change information;
retrieving link state change information from the FIFO buffer; and
transmitting the link state change information serially to an output pin of the die.