linux-kernel - Re: [PATCH net-next v2 8/9] microchip: lan865x: add driver support for Microchip's LAN865X MACPHY

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Date:   Thu, 2 Nov 2023 14:40:11 +0100
From:   Ramón Nordin Rodriguez 
        <ramon.nordin.rodriguez@...roamp.se>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Parthiban Veerasooran <Parthiban.Veerasooran@...rochip.com>,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        corbet@....net, steen.hegelund@...rochip.com,
        rdunlap@...radead.org, horms@...nel.org, casper.casan@...il.com,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        horatiu.vultur@...rochip.com, Woojung.Huh@...rochip.com,
        Nicolas.Ferre@...rochip.com, UNGLinuxDriver@...rochip.com,
        Thorsten.Kummermehr@...rochip.com
Subject: Re: [PATCH net-next v2 8/9] microchip: lan865x: add driver support
 for Microchip's LAN865X MACPHY

Hi Andrew

> > 		spi-max-frequency = <50000000>;
> 
> That is a pretty high frequency. It is actually running at that speed?

I have not verified that we're actually hitting 50M.

> 
> Have you tried lower speed?

Sorry for being too brief about the things I've tested. But yes, I've
tested running at 15MHz with the same or similar enough results that
I've not been able to discern any difference.
Meaningful to mention here as well would be that I've tested with and
without DMA as well.

> > With this setup I'm getting a maximum throughput of about 90kB/s.
> > If I increase the chunk size / oa-cps to 64 I get a might higher
> > throughput ~900kB/s, but after 0-2s I get dump below (or similar).
> 
> Is this tcp traffic? Lost packets will have a big impact. You might
> want to look at the link peer with tcpdump and look for retries. Also,
> look if there are frames with bad checksums.
> 

As you assume, this was with TCP. I'll do a run with tcpdump and see if
I can compile any intelligent statistics from that.