Re: [PATCH RFC 3/9] net: stmmac: qcom-ethqos: fix RGMII_ID mode to use DLL bypass

[Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>]

Hello Andrew,
On Thu, Jun 11, 2026 at 10:54:37PM +0200, Andrew Lunn wrote:
> On Fri, Jun 12, 2026 at 12:06:59AM +0530, Mohd Ayaan Anwar wrote:
> > When "rgmii-id" is selected the PHY supplies both TX and RX delays, so
> > the MAC must not add its own.  The driver currently falls through to the
> > generic DLL initialisation path which programs it to add a delay.
> > 
> > Power down the DLL and set DDR bypass mode for RGMII_ID, then program
> > the IO_MACRO via a new ethqos_rgmii_id_macro_init() helper.  Also fix
> > ethqos_set_clk_tx_rate() to not double the clock rate in bypass mode at
> > 100M/10M, and remove RGMII_ID from the phase-shift suppression in
> > ethqos_rgmii_macro_init() since RGMII_ID no longer reaches that path.
> 
> I'm curious how this works at the moment? Do no boards make use of
> RGMII ID? Are all current boards broken?

Searching through the DTS, I found that we have two boards using "rgmii"
(qcs404-evb-4000.dts and sa8155-adp.dts) and another board using
"rgmii-txid" (sa8540p-ride.dts). No board which uses RGMII ID.

I don't think any of these boards have extra long wires which would add
PCB level delay. They are against the netdev definitions for "rgmii" and
"rgmii-txid".

But the first two boards should still be working fine since the current
driver programs the IO_MACRO to add the delay when operating in RGMII
mode. I am not sure about the last board. I went through the different
versions of the ETHQOS programming guide, and it should reliably support
either only MAC side Rx/Tx delay -or- bypass mode (no MAC side delay),
with each having different clock requirements.

	Ayaan