.. SPDX-License-Identifier: GPL-2.0

======================================= stmmac (synopsys dwmac) devlink support

This document describes the devlink features implemented by the stmmac device driver.

Parameters

The stmmac driver implements the following driver-specific parameters.

.. list-table:: Driver-specific parameters implemented :widths: 5 5 5 85

• • Name
  • Type
  • Mode
  • Description

• • phc_coarse_adj

  • Boolean

  • runtime

  • Enable the Coarse timestamping mode, as defined in the DWMAC TRM. A detailed explanation of this timestamping mode can be found in the Socfpga Functionnal Description [1].

    In Coarse mode, the ptp clock is expected to be fed by a high-precision clock that is externally adjusted, and the subsecond increment used for timestamping is set to 1/ptp_clock_rate.

    In Fine mode (i.e. Coarse mode == false), the ptp clock frequency is continuously adjusted, but the subsecond increment is set to 2/ptp_clock_rate.

    Coarse mode is suitable for PTP Grand Master operation. If unsure, leave the parameter to False.

    [1] https://www.intel.com/content/www/us/en/docs/programmable/683126/21-2/functional-description-of-the-emac.html