net: phy: Support overriding Auto Negotiation timeout with env variable

The Auto Negotiation procedure between two Ethernet PHYs consists of
determining the best commonly supported parameters among Speed,
Duplex Mode and Flow Control.

The time taken for this procedure is not only dependent on the local
PHY used, but also on the link-partner PHY.

While a timeout can be specified in the form of a "CONFIG" on the basis
of the local PHY present on the device, since the timeout also depends
on the link-partner PHY, it might be necessary to modify the timeout.

To avoid rebuilding the bootloader for a given device, just because it
may be connected to various link-partner PHYs, each with a different
timeout, introduce an environment variable named "phy_aneg_timeout" and
override "CONFIG_PHY_ANEG_TIMEOUT" with "phy_aneg_timeout".

Signed-off-by: Siddharth Vadapalli <[email protected]>
Acked-by: Jerome Forissier <[email protected]>
[jf: add missing #include <env.h>]
Signed-off-by: Jerome Forissier <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index bb6c351b441..77197d79380 100644
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -335,6 +335,15 @@ netretry
     Useful on scripts which control the retry operation
     themselves.
 
+phy_aneg_timeout
+    If set, the specified value will override CONFIG_PHY_ANEG_TIMEOUT.
+    This variable has the same base and unit as CONFIG_PHY_ANEG_TIMEOUT
+    which is "decimal" and "millisecond" respectively. The default value
+    of CONFIG_PHY_ANEG_TIMEOUT may be sufficient for most use-cases, but
+    certain link-partners may require a larger timeout due to the Ethernet
+    PHY they use. Alternatively, the timeout can be reduced as well if the
+    use-case demands it.
+
 rng_seed_size
     Size of random value added to device-tree node /chosen/rng-seed.
     This variable is given as a decimal number.