Telemetry

In Chip Management Firmware, telemetry reporting is done in the common file telemetry.c, with the per-SoC table and data collection in telemetry_bh.c (Blackhole) and telemetry_gr.c (Grendel). The versioned telemetry table contains a tag-to-offset mapping followed by the telemetry data. The table location and its discovery mechanism are SoC-specific.

See telemetry table for information.

On Blackhole, a Zephyr work item refreshes the telemetry data every 100 ms by default; the host can change the interval.

Procedure to Read Telemetry

1. Find telemetry_table by reading the telemetry-table scratch register for the SoC.

2. Check telemetry_table.entry_count to find out how many tag_table entries there are.

3. Read through all tag_table entries and keep the tag-offset mapping around. These will not change unless the firmware gets updated and the chip is reset.

4. To find specific telemetry entries: - Look up the offset in the tag-offset mapping. - Read 4 bytes from the telemetry data array at that offset.

Telemetry Discovery Registers

SoC	Telemetry table	Telemetry data
Wormhole	ARC_RESET.NOC_NODEID_X_0 contains the table address in tensix_sm (ARC) memory.	ARC_RESET.NOC_NODEID_Y_0 contains the data-array address.
Blackhole	reset_unit.SCRATCH_RAM[13] contains the table address in tensix_sm (ARC) memory.	reset_unit.SCRATCH_RAM[12] contains the data-array address.
Grendel	telemetry_info at Cold Scratch 4 (0xc0002810) contains the complete telemetry_table address in RISC-V SMC SRAM.	The data array follows the tag table within telemetry_table in SMC SRAM.

Via SMBUS

(i.e., from DMC or Galaxy UBB CPLD)

1. Write the tag ID you wish to read to SMBUS address 0x26. This register is 8 bits wide—the SMBUS write should include a PEC.

2. The tag ID is persistent, so it can be programmed once, and the telemetry data can be read multiple times from address 0x27.

3. Read the telemetry tag data via SMBUS by issuing a block read to address 0x27. This register is 32 bits wide.

Register	Address	Usage
TELEMETRY_TAG	0x26	Write only. Write with telemetry tag value to select which telemetry field will be read when reading from TELEMETRY_DATA register.
TELEMETRY_DATA	0x27	Read only. Read to get the latest telemetry data for the tag programmed to the TELEMETRY_TAG register.

Via west attach

You can print telemetry_table.telemetry[<OFFSET>] in gdb, where <OFFSET> is the offset for the tag in telemetry_table.tag_table.

west attach
(gdb) print telemetry_table.tag_table
(gdb) print telemetry_table.telemetry[7]
$6 = 47

Tag IDs

Tag IDs are permanent in the sense that they’ll never change meaning, but may not be present.

See telemetry group for more details.