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

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Message-ID: <CAMdnO-Lte7SfYXBhjBXoKP_LsXRvdexvUKKYBQEC2Y0jjEQYng@mail.gmail.com>
Date: Thu, 8 Aug 2024 18:49:57 -0700
From: Jitendra Vegiraju <jitendra.vegiraju@...adcom.com>
To: Andrew Lunn <andrew@...n.ch>
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

Hi Andrew

On Tue, Aug 6, 2024 at 4:13 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> 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.
>
Sorry, for the delayed response.
We got confirmation that HDMA capability can be identified by the
presence of DWXGMAC_CORE_4_xx and device_id 0x55.

> 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?
The initial information I got on this is that user versions are
allocated and reserved by Synopsis.
We probably don't need to key off this information now.
>
>         Andrew