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1.. SPDX-License-Identifier: GPL-2.0
2
3=======================================
4stmmac (synopsys dwmac) devlink support
5=======================================
6
7This document describes the devlink features implemented by the ``stmmac``
8device driver.
9
10Parameters
11==========
12
13The ``stmmac`` driver implements the following driver-specific parameters.
14
15.. list-table:: Driver-specific parameters implemented
16 :widths: 5 5 5 85
17
18 * - Name
19 - Type
20 - Mode
21 - Description
22 * - ``phc_coarse_adj``
23 - Boolean
24 - runtime
25 - Enable the Coarse timestamping mode, as defined in the DWMAC TRM.
26 A detailed explanation of this timestamping mode can be found in the
27 Socfpga Functionnal Description [1].
28
29 In Coarse mode, the ptp clock is expected to be fed by a high-precision
30 clock that is externally adjusted, and the subsecond increment used for
31 timestamping is set to 1/ptp_clock_rate.
32
33 In Fine mode (i.e. Coarse mode == false), the ptp clock frequency is
34 continuously adjusted, but the subsecond increment is set to
35 2/ptp_clock_rate.
36
37 Coarse mode is suitable for PTP Grand Master operation. If unsure, leave
38 the parameter to False.
39
40 [1] https://www.intel.com/content/www/us/en/docs/programmable/683126/21-2/functional-description-of-the-emac.html