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

["Katakam, Harini" <harini.katakam@amd.com>]

Hi Vladimir,

> -----Original Message-----
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> Sent: Wednesday, April 26, 2023 7:49 PM
> To: Katakam, Harini <harini.katakam@amd.com>
> Cc: robh+dt@kernel.org; andrew@lunn.ch; hkallweit1@gmail.com;
> linux@armlinux.org.uk; davem@davemloft.net; kuba@kernel.org;
> edumazet@google.com; pabeni@redhat.com; wsa+renesas@sang-
> engineering.com; krzysztof.kozlowski+dt@linaro.org;
> simon.horman@corigine.com; netdev@vger.kernel.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> harinikatakamlinux@gmail.com; Simek, Michal <michal.simek@amd.com>;
> Pandey, Radhey Shyam <radhey.shyam.pandey@amd.com>
> Subject: Re: [PATCH net-next v2 3/3] phy: mscc: Add support for VSC8531_02
> with RGMII tuning
> 
> 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.

Thanks, yes I noticed the difference here and also in older PHY drivers that
used custom properties (see dp83867 which is what I originally aligned it to).
But the table you mentioned above makes sense; I'll re-spin accordingly.

> My interpretation was based on the wording from the dt-bindings document,
> which seems to suggest that rx-internal-delay-ps takes precedence.

OK I understand.

Regards,
Harini