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Message-ID: <0f0df372-29b5-4daf-8e54-4157e8ab1a98@quicinc.com>
Date: Mon, 3 Jun 2024 16:45:30 +0530
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Subject: Re: [PATCH net-next] net: stmmac: dwmac-qcom-ethqos: Add support for
 2.5G SGMII
To: "Russell King (Oracle)" <linux@armlinux.org.uk>,
        Andrew Lunn
	<andrew@lunn.ch>
CC: Andrew Halaney <ahalaney@redhat.com>, Vinod Koul <vkoul@kernel.org>,
        Bhupesh Sharma <bhupesh.sharma@linaro.org>,
        Alexandre Torgue
	<alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        "David S.
 Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        "Jakub
 Kicinski" <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        Maxime Coquelin
	<mcoquelin.stm32@gmail.com>, <netdev@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        <kernel@quicinc.com>
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From: Sneh Shah <quic_snehshah@quicinc.com>
In-Reply-To: <ZleMdFsmQzXGp1GM@shell.armlinux.org.uk>
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On 5/30/2024 1:43 AM, Russell King (Oracle) wrote:
> On Wed, May 29, 2024 at 04:28:16PM +0200, Andrew Lunn wrote:
>>> Qualcomm ethernet HW supports 2.5G speed in overclocked SGMII mode.
>>> we internally term it as OCSGMII.
>>
>> So it still does SGMII inband signalling? Not 2500BaseX signalling? It
>> is not actually compatible with 2500BaseX?
>>
>>> End goal of these patches is to enable SGMII with 2.5G speed support.
>>> The patch in these series enabled up SGMII with 2.5 for cases where we
>>> don't have external phy. ( mac-to-mac connectivity)
>>
>> So the other end needs to be an over clocked SGMII MAC, not 2500BaseX?
>>
>>> The new patch posted extends this for the case when the MAC has an
>>> external phy connected. ( hence we are advertising fr 2.5G speed by adding
>>> 2500BASEX as supported interface in phylink)
>>
>> And i assume it does not actually work against a true 2500BaseX
>> device, because it is doing SGMII inband signalling?
> 
> I really hope the hardware isn't using any SGMII inband signalling
> at 2.5G speeds. Other devices explicitly state that SGMII inband
> signalling while operating the elevated 2.5G speed is *not* supported!

Do we mean SGMII autoneg by SGMII inband signalling? Our hardware doesn't
support autoneg for 2.5G mode in SGMII.
>