Re: [linux-next-v2 1/5] arm64: dts: rockchip: Fix gmac phy mode to rgmii on Rock 3A SBC.

[Anand Moon <linux.amoon@gmail.com>]

Hi Peter

On Thu, 17 Nov 2022 at 02:06, Peter Geis <pgwipeout@gmail.com> wrote:
>
> On Wed, Nov 16, 2022 at 3:02 PM Anand Moon <linux.amoon@gmail.com> wrote:
> >
> > On rk356x ethernet phy support reduced media independent interface (RMII)
> > and reduced gigabit media independent interface (RGMII).
> > So set the phy mode to rgmii to support clock delay, also
> > add TX and RX delay for phy-mode.
>
> Controller based clock delay, the various rgmii-id modes (rgmii-txid
> and rgmii-rxid are also valid) apply the delays in the phy. They are
> usually at a fixed amount, but some phys support variable delays.
>
> You want your commit message to accurately describe the problem, such
> as "In rgmii-id mode, the phy on the rock-3a is unreliable due to
> incorrect delays. Switch to rgmii mode in order to handle the delays
> in the controller."
>
> >
> > Fix following warning
> >
> > [    7.365215] rk_gmac-dwmac fe010000.ethernet: Can not read property: tx_delay.
> > [    7.365219] rk_gmac-dwmac fe010000.ethernet: set tx_delay to 0x30
> > [    7.365224] rk_gmac-dwmac fe010000.ethernet: Can not read property: rx_delay.
> > [    7.365228] rk_gmac-dwmac fe010000.ethernet: set rx_delay to 0x10
>
> I've been meaning to make this a dev_debug message, because in the
> various rgmii-id modes it is feasible for these to be non-existent in
> the device-tree. In rgmii-id mode these are disabled, no matter what
> they are set to in the dt.

As per the public datasheet share by Radxa below
[0] https://dl.radxa.com/rock3/docs/hw/datasheet/RTL8211F-CG-Datasheet.pdf

This Ethernet controller supports RGMII mode.

>
> >
> > Signed-off-by: Anand Moon <linux.amoon@gmail.com>
> > ---
> > V2: Fix commit message and added the RX and TX clock delay.
> > ---
> >  arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts b/arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts
> > index ea74ba32fbbd..e1c75532dcee 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts
> > +++ b/arch/arm64/boot/dts/rockchip/rk3568-rock-3a.dts
> > @@ -253,13 +253,16 @@ &gmac1 {
> >         assigned-clock-rates = <0>, <125000000>;
> >         clock_in_out = "output";
> >         phy-handle = <&rgmii_phy1>;
> > -       phy-mode = "rgmii-id";
> > +       phy-mode = "rgmii";
> >         pinctrl-names = "default";
> >         pinctrl-0 = <&gmac1m1_miim
> >                      &gmac1m1_tx_bus2
> >                      &gmac1m1_rx_bus2
> >                      &gmac1m1_rgmii_clk
> >                      &gmac1m1_rgmii_bus>;
> > +
> > +       tx_delay = <0x4f>;
> > +       rx_delay = <0x26>;
>
> These are pretty far off from the default, have you verified the upper
> and lower bounds for the rock-3a? These should be roughly in the
> middle of that range.
>
No I have not tested this way but as per the datasheet, it supports

TXDLY   Add 2ns delay to RXC for RXD latching (via 4.7k-ohm to DVDD_RG)
RXDLY   Add 2ns delay to RXC for RXD latching (via 4.7k-ohm to DVDD_RG)

I feel I should ignore the above warning and add it below.

rx-internal-delay-ps = <2000>;
tx-internal-delay-ps = <2000>;

Thanks
-Anand
> >         status = "okay";
> >  };
> >
> > --
> > 2.38.1
> >