netdev - Re: [PATCH 1/3] net: ethernet: stmmac: dwmac-rk: Disable delayline if it is invalid

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Date:   Fri, 24 Jun 2022 19:43:51 -0400
From:   Peter Geis <pgwipeout@...il.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        David Wu <david.wu@...k-chips.com>, kernel@...labora.com
Subject: Re: [PATCH 1/3] net: ethernet: stmmac: dwmac-rk: Disable delayline if
 it is invalid

On Fri, Jun 24, 2022 at 4:16 PM Sebastian Reichel
<sebastian.reichel@...labora.com> wrote:
>
> Hi,
>
> On Fri, Jun 24, 2022 at 07:37:08PM +0200, Andrew Lunn wrote:
> > > The Rockchip hardware supports enabling/disabling delays and
> > > configuring a delay value of 0x00-0x7f. For the RK3588 evaluation
> > > board the RX delay should be disabled.
> >
> > So you can just put 0 in DT then.
>
> My understanding is, that there is a difference between
> enabled delay with a delay value of 0 and delay fully
> disabled. But I could not find any details aboout this
> in the datasheet unfortunately.

The driver already sets the delays to 0 in case of the rgmii-id modes.
0 is disabled, even in this patch. The only thing this patch does is
change the behavior when the delays are not set. If the rx delays
should be 0, they should be defined as 0 in the device tree. There is
rgmii-rxid for a reason as well, but if they are setting the rx delay
to 0 with rgmii that implies this hardware is fundamentally broken.

Very Respectfully,
Peter Geis

>
> -- Sebastian
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip

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