linux-kernel - Re: [RFC] net: dsa: qca8k: implement rgmii-id mode

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Message-ID: <20190218104539.GL21884@vkoul-mobl>
Date:   Mon, 18 Feb 2019 16:15:39 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Michal Vokáč <michal.vokac@...ft.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [RFC] net: dsa: qca8k: implement rgmii-id mode

On 15-02-19, 16:23, Andrew Lunn wrote:
> On Fri, Feb 15, 2019 at 04:01:08PM +0100, Michal Vokáč wrote:
> > Hi,
> > 
> > networking on my boards [1], which are currently in linux-next, suddently
> > stopped working. I tracked it down to this commit 5ecdd77c61c8 ("net: dsa:
> > qca8k: disable delay for RGMII mode") [2].
> > 
> > So I think the rgmii-id mode is obviously needed in my case.
> > I was able to find a couple drivers that read tx/rx-delay or
> > tx/rx-internal-delay from device tree. Namely:
> > 
> >   drivers/net/ethernet/apm/xgene/xgene_enet_main.c
> >   drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c
> >   drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c
> >   drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> >   drivers/net/phy/dp83867.c
> > 
> > I would appreciate any hints how to add similar function to qca8k driver
> > if that is the correct way to go. Can I take some of the above mentioned
> > drivers as a good example for that? How should the binding look like?
> > 
> > I would expect something like this:
> > 
> > 	switch@0 {
> > 		compatible = "qca,qca8334";
> > 		reg = <0>;
> > 
> > 		switch_ports: ports {
> > 			#address-cells = <1>;
> > 			#size-cells = <0>;
> > 
> > 			ethphy0: port@0 {
> > 				reg = <0>;
> > 				label = "cpu";
> > 				phy-mode = "rgmii-id";
> > 				qca,tx-delay = <3>;
> > 				qca,rx-delay = <3>;
> > 				ethernet = <&fec>;
> > 		};
> 
> Hi Michal
> 
> Your submission used:
> 
> +				ethphy0: port@0 {
> +					reg = <0>;
> +					label = "cpu";
> +					phy-mode = "rgmii";
> +					ethernet = <&fec>;
> +
> +					fixed-link {
> +						speed = <1000>;
> +						full-duplex;
> +					};
> +				};
> 
> This is good. If you have a fixed-link you can pass a phy-mode.
> 
> The comment that was removed was:
> 
> -               /* According to the datasheet, RGMII delay is enabled through
> -                * PORT5_PAD_CTRL for all ports, rather than individual port
> -                * registers
> -                */
> 
> Is it possible to enable delays per port? Ideally, you want to enable
> delays for just selected ports. Add another case for
> PHY_INTERFACE_MODE_RGMII_ID to enable the delays.

In the hindsight I should not have removed the comment, let me ressurect
that as well as add handling of the RGMII modes...

Please do test

Thanks
-- 
~Vinod