linux-kernel - Re: [PATCH net-next 2/3] net: stmmac: xgmac: Correct supported speed modes

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Message-ID: <a71897db-5337-4ee9-a957-3e68dee03afb@altera.com>
Date: Fri, 25 Jul 2025 14:48:02 +0530
From: "G Thomas, Rohan" <rohan.g.thomas@...era.com>
To: Serge Semin <fancer.lancer@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Romain Gantois <romain.gantois@...tlin.com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Matthew Gerlach <matthew.gerlach@...era.com>
Subject: Re: [PATCH net-next 2/3] net: stmmac: xgmac: Correct supported speed
 modes

On 7/24/2025 11:26 PM, Serge Semin wrote:
>>> DW XGMAC IP-core of v2.x and older don't support 10/100Mbps modes
>>> neither in the XGMII nor in the GMII interfaces. That's why I dropped
>>> the 10/100Mbps link capabilities retaining 1G, 2.5G and 10G speeds
>>> only (the only speeds supported for DW XGMAC 1.20a/2.11a Tx in the
>>> MAC_Tx_Configuration.SS register field). Although I should have
>>> dropped the MAC_5000FD too since it has been supported since v3.0
>>> IP-core version. My bad.(
>>>
>>> Starting from DW XGMAC v3.00a IP-core the list of the supported speeds
>>> has been extended to: 10/100Mbps (MII), 1G/2.5G (GMII), 2.5G/5G/10G
>>> (XGMII). Thus the more appropriate fix here should take into account
>>> the IP-core version. Like this:
>>> 	if (dma_cap->mbps_1000 && MAC_Version.SNPSVER >= 0x30)
>>> 		dma_cap->mbps_10_100 = 1;
>>>
>>> Then you can use the mbps_1000 and mbps_10_100 flags to set the proper
>>> MAC-capabilities to hw->link.caps in the dwxgmac2_setup() method. I
>>> would have added the XGMII 2.5G/5G MAC-capabilities setting up to the
>>> dwxgmac2_setup() method too for the v3.x IP-cores and newer.
>>
Hi Serge,

Apologies for the multiple emails. I wanted to check specifically on the
support for 2.5G/5G over XGMII and GMII interfaces. I’ve reviewed the
v3.10a databook, but it doesn’t mention when support for these speeds
was first introduced. Could you please confirm on this?

Best Regards,
Rohan