linux-kernel - Re: [PATCH net-next v3 2/3] net: stmmac: Integrate dwxgmac4 into stmmac hwif handling

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Message-ID: <e6b4fc20-a861-4f24-9881-f8151fe66351@lunn.ch>
Date: Wed, 7 Aug 2024 01:13:27 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
Cc: netdev@...r.kernel.org, alexandre.torgue@...s.st.com,
	joabreu@...opsys.com, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, mcoquelin.stm32@...il.com,
	bcm-kernel-feedback-list@...adcom.com, richardcochran@...il.com,
	ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
	john.fastabend@...il.com, linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, bpf@...r.kernel.org,
	linux@...linux.org.uk, horms@...nel.org,
	florian.fainelli@...adcom.com
Subject: Re: [PATCH net-next v3 2/3] net: stmmac: Integrate dwxgmac4 into
 stmmac hwif handling

On Mon, Aug 05, 2024 at 05:36:30PM -0700, Jitendra Vegiraju wrote:
> Hi Andrew,
> On Fri, Aug 2, 2024 at 3:59 PM Andrew Lunn <andrew@...n.ch> wrote:
> >
> > > +     user_ver = stmmac_get_user_version(priv, GMAC4_VERSION);
> > > +     if (priv->synopsys_id == DWXGMAC_CORE_4_00 &&
> > > +         user_ver == DWXGMAC_USER_VER_X22)
> > > +             mac->dma = &dwxgmac400_dma_ops;
> >
> > I know nothing about this hardware....
> >
> > Does priv->synopsys_id == DWXGMAC_CORE_4_0 not imply
> > dwxgmac400_dma_ops?
> >
> > Could a user synthesise DWXGMAC_CORE_4_00 without using
> > dwxgmac400_dma_ops? Could dwxgmac500_dma_ops or dwxgmac100_dma_ops be
> > used?
> Yes, the user can choose between Enhanced DMA , Hyper DMA , Normal DMA.
> This SoC support has chosen Hyper DMA for future expandability.

Is there a register which describes the synthesis configuration? It is
much better that the hardware tells us what it is, rather than having
to expand this condition for every new devices which gets added.

Also, what is the definition of user_ver. Can we guarantee this is
unique and can actually be used to determine what DMA variant has been
synthesised?

	Andrew