Messages in this thread | | | Date | Tue, 21 Feb 2023 13:51:55 -0800 | Subject | Re: BCM54220: After the BCM54220 closes the auto-negotiation, the configuration forces the 1000M network port to be linked down all the time. | From | Doug Berger <> |
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On 2/21/2023 11:53 AM, Doug Berger wrote: > On 2/21/2023 11:41 AM, Andrew Lunn wrote: >> On Tue, Feb 21, 2023 at 10:44:44AM -0800, Doug Berger wrote: >>> On 2/17/2023 12:06 AM, Wang, Xiaolei wrote: >>>> hi >>>> >>>> When I use the nxp-imx7 board, eth0 is connected to the PC, >>>> eth0 is turned off the auto-negotiation mode, and the configuration >>>> is forced to 10M, 100M, 1000M. When configured to force 1000M, >>>> The link status of phy status reg(0x1) is always 0, and the >>>> chip of phy is BCM54220, but I did not find the relevant datasheet >>>> on BCM official website, does anyone have any suggestions or the >>>> datasheet of BCM54220? >>>> >>>> thanks >>>> xiaolei >>>> >>> It is my understanding that the 1000BASE-T PHY requires peers to take on >>> asymmetric roles and that establishment of these roles requires >>> negotiation >>> which occurs during auto-negotiation. Some PHYs may allow manual >>> programming >>> of these roles, but it is not standardized and tools like ethtool do not >>> support manual specification of such details. >> >> Are you talking about ethtool -s >> [master-slave|preferred-master|preferred-slave|forced-master|forced-slave] >> > I am, though I was not aware of their addition to ethtool and I avoided > referencing them by name out of an overabundance of political > correctness ;). > > Thanks for bringing this to my attention. > >> The broadcom PHYs call genphy_config_aneg() -> __genphy_config_aneg() >> -> genphy_setup_master_slave() which should configure this, even when >> auto-neg is off. > Yes, this sounds good. Perhaps Xiaolei is not setting these properly > when forcing 1000. > Hmmm. I just revisited 802.3-2018 40.5.2 MASTER-SLAVE configuration resolution and I see it contains this statement: The MASTER-SLAVE relationship shall be determined during Auto-Negotiation using Table 40–5 with the 1000BASE-T Technology Ability Next Page bit values specified in Table 40–4 and information received from the link partner.
So it appears that the only normative behavior requires Auto-Negotiation to be enabled. It seems reasonable that an implementation might allow the forced-master and forced-slave configurations to be applied when Auto-Negotiation is not enabled, but this case is outside of the standard so an implementation could also fail to establish a link.
>> >> Andrew > Thanks again! > Doug
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