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

[Jitendra Vegiraju]

Hi Andrew

On Tue, Aug 6, 2024 at 4:13 PM Andrew Lunn <andrew@xxxxxxx> 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@xxxxxxx> 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