netdev - Re: [PATCH v1 2/2] net: stmmac: Add NPCM support

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Date: Thu, 30 Nov 2023 19:17:22 +0200
From: Tomer Maimon <tmaimon77@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: alexandre.torgue@...s.st.com, tali.perry1@...il.com, edumazet@...gle.com, 
	krzysztof.kozlowski+dt@...aro.org, linux-stm32@...md-mailman.stormreply.com, 
	benjaminfair@...gle.com, openbmc@...ts.ozlabs.org, joabreu@...opsys.com, 
	joel@....id.au, devicetree@...r.kernel.org, j.neuschaefer@....net, 
	robh+dt@...nel.org, peppe.cavallaro@...com, 
	linux-arm-kernel@...ts.infradead.org, avifishman70@...il.com, 
	venture@...gle.com, linux-kernel@...r.kernel.org, mcoquelin.stm32@...il.com, 
	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH v1 2/2] net: stmmac: Add NPCM support

Hi Andrew,


On Wed, 29 Nov 2023 at 01:31, Andrew Lunn <andrew@...n.ch> wrote:
>
> On Mon, Nov 27, 2023 at 05:19:15PM +0200, Tomer Maimon wrote:
> > Hi Andrew,
> >
> > I took a look at the xpcs driver and the stmmac driver and it doesn't
> > cover NPCM use.
> >
> > in the NPCM case the stmmac ID=0x37 therefore the driver is linked to DWMAC1000
> > https://elixir.bootlin.com/linux/v6.7-rc2/source/drivers/net/ethernet/stmicro/stmmac/hwif.c#L139
> >
> > to enable the xpcs, the stmmac should support xgmac or gmac4 and in
> > the NPCM is support only gmac.
> > https://elixir.bootlin.com/linux/v6.7-rc2/source/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c#L555
> > https://elixir.bootlin.com/linux/v6.7-rc2/source/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c#L573
> >
> > and the most important thing is that the XPCS is handled through an
> > indirect register access and not through MDIO. the MDIO is connected
> > to the external PHY and not to the XPCS.
>
> What really matters here is, is the PCS hardware block you have an
> XPCS? We don't want two drivers for the same block of hardware.
>
> MDIO vs indirect register access can be solved with a bit of
> layering. That is not a reason to write a second driver.
I will check with the xpcs maintainer how can we add indirect access
to the xpcs module.
>
>         Andrew

Thanks.

Tomer