linux-kernel - Re: [PATCH] net: thunderx: use proper interface type for RGMII

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Date:   Wed, 12 Feb 2020 08:55:39 -0800
From:   Tim Harvey <tharvey@...eworks.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, rrichter@...vell.com,
        linux-arm-kernel@...ts.infradead.org,
        David Miller <davem@...emloft.net>, sgoutham@...vell.com
Subject: Re: [PATCH] net: thunderx: use proper interface type for RGMII

On Fri, Feb 7, 2020 at 1:02 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Fri, Feb 07, 2020 at 12:40:26PM -0800, Tim Harvey wrote:
> > The configuration of the OCTEONTX XCV_DLL_CTL register via
> > xcv_init_hw() is such that the RGMII RX delay is bypassed
> > leaving the RGMII TX delay enabled in the MAC:
> >
> >       /* Configure DLL - enable or bypass
> >        * TX no bypass, RX bypass
> >        */
> >       cfg = readq_relaxed(xcv->reg_base + XCV_DLL_CTL);
> >       cfg &= ~0xFF03;
> >       cfg |= CLKRX_BYP;
> >       writeq_relaxed(cfg, xcv->reg_base + XCV_DLL_CTL);
> >
> > This would coorespond to a interface type of PHY_INTERFACE_MODE_RGMII_RXID
> > and not PHY_INTERFACE_MODE_RGMII.
> >
> > Fixing this allows RGMII PHY drivers to do the right thing (enable
> > RX delay in the PHY) instead of erroneously enabling both delays in the
> > PHY.
>
> Hi Tim
>
> This seems correct. But how has it worked in the past? Does this
> suggest there is PHY driver out there which is doing the wrong thing
> when passed PHY_INTERFACE_MODE_RGMII?
>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
>

Andrew,

Yes, the DP83867 phy driver used on the Gateworks Newport boards would
configure the delay in an incompatible way when enabled.

Tim