[PATCH] net: phy: Support overriding Auto Negotiation timeout with env variable

[Marek Vasut]

On 7/22/25 8:05 AM, Siddharth Vadapalli wrote:
> 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 <s-vadapalli at ti.com>
> ---
> 
> Hello,
> 
> This patch is based on commit
> 7598b469c16 Merge tag 'u-boot-dfu-next-20250703' of https://source.denx.de/u-boot/custodians/u-boot-dfu into next
> of the next branch of Mainline U-Boot.
> 
> Patch has been tested on J784S4-EVM validating the following cases:
> 1. PHY Auto-Negotiation performed with "phy_aneg_timeout" unset.
>     CONFIG_PHY_TIMEOUT with a value of 4,000 takes effect.
>     => Auto Negotiation succeeds
> 2. PHY Auto-Negotiation performed with "phy_aneg_timeout" set to 10,000.
>     "phy_aneg_timeout" overrides CONFIG_PHY_TIMEOUT.
>     [Higher value than default specified by CONFIG_PHY_ANEG_TIMEOUT]
>     => Auto Negotiation succeeds
> 3. PHY Auto-Negotiation performed with "phy_aneg_timeout" set to 2,000.
>     "phy_aneg_timeout" overrides CONFIG_PHY_TIMEOUT.
>     [Lower value than default specified by CONFIG_PHY_ANEG_TIMEOUT]
>     => Auto Negotiation times out
> 
> Test Logs:
> https://gist.github.com/Siddharth-Vadapalli-at-TI/697eadcbb26786435df48a834c968375
> 
> Regards,
> Siddharth.
> 
>   doc/usage/environment.rst | 8 ++++++++
>   drivers/net/phy/phy.c     | 6 +++++-
>   2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
> index bb6c351b441..7447bb85d3e 100644
> --- a/doc/usage/environment.rst
> +++ b/doc/usage/environment.rst
> @@ -335,6 +335,14 @@ netretry
>       Useful on scripts which control the retry operation
>       themselves.
>   
> +phy_aneg_timeout
> +    If set, the specified value will override CONFIG_PHY_ANEG_TIMEOUT
> +    which defaults to 4000. 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.
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index e6fed8c41d7..0f5c9685b59 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -9,6 +9,7 @@
>    */
>   #include <console.h>
>   #include <dm.h>
> +#include <env.h>
>   #include <log.h>
>   #include <malloc.h>
>   #include <net.h>
> @@ -243,6 +244,9 @@ int genphy_update_link(struct phy_device *phydev)
>   	if ((phydev->autoneg == AUTONEG_ENABLE) &&
>   	    !(mii_reg & BMSR_ANEGCOMPLETE)) {
>   		int i = 0;
> +		char *s = env_get("phy_aneg_timeout");
env_get_ulong("phy_aneg_timeout", 10, CONFIG_PHY_ANEG_TIMEOUT);