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.. 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
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