Re: [PATCH net-next v2 3/3] phy: mscc: Add support for VSC8531_02 with RGMII tuning

[Vladimir Oltean <vladimir.oltean@nxp.com>]

On Wed, Apr 26, 2023 at 12:21:47PM +0000, Katakam, Harini wrote:
> Thanks for the review.
> The intention is to have the following precedence (I'll rephrase the commit if required)
> -> If phy-mode is rgmii, current behavior persists for all devices
> -> If phy-mode is rgmii-id/rgmii-rxid/rgmii-txid, current behavior persists for all devices
> (i.e. delay of RGMII_CLK_DELAY_2_0_NS)
> -> If phy-mode is rgmii-id/rgmii-rxid/rgmii-txid AND rx-internal-delay-ps/tx-internal-delay-ps
> is defined, then the value from DT is considered instead of 2ns. (NOT irrespective of phy-mode)
> 
> I'm checking the phy drivers that use phy_get_internal_delay and the description phy-mode
> in ethernet-controller.yaml and rx/tx-internal-delay-ps in ethernet-phy.yaml. It does look like
> the above is allowed. Please do let me know otherwise.

I understood what your intention was. What I meant was:

 phy-mode                       rgmii                          rgmii-rxid/rgmii-id
 --------------------------------------------------------------------------------------------
 rx-internal-delay-ps absent    0.2 ns                         2 ns
 rx-internal-delay-ps present   follow rx-internal-delay-ps    follow rx-internal-delay-ps

I agree with Andrew that probably there isn't consistency among PHY
drivers for this interpretation - see dp83822 vs intel-xway for example.
My interpretation was based on the wording from the dt-bindings document,
which seems to suggest that rx-internal-delay-ps takes precedence.