cable_safety_feature: Add cable fault detection and low-power mode#982
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ShLiTT wants to merge 3 commits intotenstorrent:mainfrom
Open
cable_safety_feature: Add cable fault detection and low-power mode#982ShLiTT wants to merge 3 commits intotenstorrent:mainfrom
ShLiTT wants to merge 3 commits intotenstorrent:mainfrom
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- added `DMC_CABLE_POWER_LIMIT_REG_ADDR` definition using RESET_UNIT_SCRATCH_REG_ADDR(1) -- SCRATCH_1 - added cable_fault bit (bit 1) to STATUS_ERROR_STATUS0_reg_t Signed-off-by: Sherry Li <xiaoruli@tenstorrent.com>
Implemented cable power limit communication from DMC to SMC: - Added jtag_bootrom_set_cable_power_limit() to write power limit to SCRATCH_1 register via JTAG AXI - Added cable_power_limit parameter to jtag_bootrom_reset_sequence() to write power limit after ASIC reset but before ARC soft reset - Added cable_power_limit field to bh_chip_data to preserve the value for runtime resets - DMC calls detect_max_power() and passes result to reset sequence Signed-off-by: Sherry Li <xiaoruli@tenstorrent.com>
Read cable power limit from SCRATCH_1 (written by DMC via JTAG). If power limit is 0, enter cable fault mode to minimize power draw. Add magic bits for backward compatibility In cable fault mode: - Keep tensixes, ETH, GDDR, and L2CPU in reset - Always deassert NOC, system, and PCIe resets (needed for ARC-PCIe communication path) - Skip RISC-V and soft reset sequences This allows the board to remain accessible via PCIe even when the 12V-2x6 power cable is missing or improperly installed. Signed-off-by: Sherry Li <xiaoruli@tenstorrent.com>
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Summary
This PR implements cable fault detection to protect the board when the 12V-2x6 power cable is missing or improperly installed. When a cable fault is detected, the SMC enters a low-power mode while maintaining PCIe communication with the host.
Problem
Without proper power cable detection, the board may attempt to power up components that could draw excessive current from the PCIe slot, damaging the cable.
Solution
DMC Side:
SMC Side: