Telemetry

In Chip Management Firmware, telemetry gathering and reporting is done in the file telemetry.c. This telemetry is located within the tensix_sm (ARC) memory space (i.e., within NOC0 8-0):

See telemetry table for information.

Scratch Registers

As per:

Scratch Registers | arc_ss.reset_unit.SCRATCH_RAM[0..63]:

Address of telemetry_data is stored in reset_unit.SCRATCH_RAM[12] (WH: ARC_RESET.NOC_NODEID_Y_0)
Address of telemetry_table is stored in reset_unit.SCRATCH_RAM[13] (WH: ARC_RESET.NOC_NODEID_X_0)

The telemetry table is updated every 100ms by a Zephyr worker thread.

Procedure to Read Telemetry

Via MMIO Access to ARC Memory

(Generally, when you are connected to BH over PCIe)

Find telemetry_table by reading `reset_unit.SCRATCH_RAM[13].
Check telemetry_table.entry_count to find out how many tag_table entries there are.
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.
To find specific telemetry entries: - Look up the offset in the tag-offset mapping. - Read 4 bytes starting from SCRATCH_RAM[12] + 4 * offset.

Via SMBUS

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

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.
The tag ID is persistent, so it can be programmed once, and the telemetry data can be read multiple times from address 0x27.
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[<TAG>] in gdb.

west attach
(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.