On 2024-12-10 12:09, Andrew Lunn wrote:
As previously mentioned, using 'rgmii' will enable EMAC to provide the delay
while disabling the delay for EPHY. So there's won't be double delay.
Additionally, the current implementation of the QCOM driver code exclusively
supports this mode, with the entire initialization sequence of EMAC designed
and fixed for this specific mode.
OK. If it is impossible to disable these delays, you need to validate
phy-mode. Only rgmii-id is allowed. Anybody trying to build a board
using extra long clock lines is out of luck. It does not happen very
often, but there are a small number of boards which do this, and the
definitions of phy-mode are designed to support them.
I'm not sure if there's a disagreement about the definition or a
misunderstanding with other vendors. From my understanding, 'rgmii' should
not imply that the delay must be provided by the board, based on both the
definition in the dt-binding file and the implementations by other EMAC
vendors. Most EMAC drivers provide the delay in this mode.
Nope. You are wrong. I've been enforcing this meaning for maybe the
last 10 years. You can go search the email archive for netdev. Before
that, we had a bit of a mess, developers were getting it wrong, and
reviewing was not as good. And i don't review everything, so some bad
code does get passed me every so often, e.g. if found out today that
TI AM62 got this wrong, they hard code TX delays in the MAC, and DT
developers have been using rgmii-rxid, not rgmii-id, and the MAC
driver is missing the mask operation before calling phy_connect.
I confirmed that there is no delay on the qcs615-ride board., and the QCOM
EMAC driver will adds the delay by shifting the clock after receiving
PHY_INTERFACE_MODE_RGMII.
Which is wrong. Because you cannot disable the delay,
PHY_INTERFACE_MODE_RGMII should return in EINVAL, or maybe
EOPNOTSUPP. Your hardware only supports PHY_INTERFACE_MODE_RGMII_ID,
and you need to mask what you pass to phylib/phylink to make it clear
the MAC has added the delays.
Andrew
I intend to follow these steps. Could you please check if they are correct?
1. Add a new flag in DTS to inform the MAC driver to include the delay
when configured with 'rgmii-id'. Without this flag, the MAC driver will
not be aware of the need for the delay.
2. In the driver, if this flag is set to true, change the phy_mode to
PHY_INTERFACE_MODE_RGMII to instruct the PHY not to add the delay.
--
Best Regards,
Yijie
