Re: [PATCH v1 3/6] ARM: dts: lan966x: add all flexcom usart nodes

[Michael Walle]

Am 2022-03-07 12:53, schrieb Claudiu.Beznea@xxxxxxxxxxxxx:
> On 04.03.2022 13:01, Michael Walle wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know 
> > the
> > content is safe
> >
> > Hi,
> >
> > thanks for the quick review.
> >
> > Am 2022-03-04 09:30, schrieb Claudiu.Beznea@xxxxxxxxxxxxx:
> > > On 03.03.2022 18:03, Michael Walle wrote:
> > > > EXTERNAL EMAIL: Do not click links or open attachments unless you 
> > > > know
> > > > the content is safe
> > > >
> > > > Add all the usart nodes for the flexcom block. There was already
> > > > an usart node for the flexcom3 block. But it missed the DMA
> > > > channels.
> > >
> > > And it would be good to go though a different patch.
> >
> > sure
> >
> > > > Although the DMA channels are specified, DMA is not
> > > > enabled by default because break detection doesn't work with DMA.
> > > >
> > > > Keep the nodes disabled by default.
> > > >
> > > > Signed-off-by: Michael Walle <michael@xxxxxxxx>
> > > > ---
> > > >  arch/arm/boot/dts/lan966x.dtsi | 55
> > > > ++++++++++++++++++++++++++++++++++
> > > >  1 file changed, 55 insertions(+)
> > > >
> > > > diff --git a/arch/arm/boot/dts/lan966x.dtsi
> > > > b/arch/arm/boot/dts/lan966x.dtsi
> > > > index a7d46a2ca058..bea69b6d2749 100644
> > > > --- a/arch/arm/boot/dts/lan966x.dtsi
> > > > +++ b/arch/arm/boot/dts/lan966x.dtsi
> > > > @@ -92,6 +92,19 @@ flx0: flexcom@e0040000 {
> > > >                         #size-cells = <1>;
> > > >                         ranges = <0x0 0xe0040000 0x800>;
> > > >                         status = "disabled";
> > > > +
> > > > +                       usart0: serial@200 {
> > > > +                               compatible =
> > > > "atmel,at91sam9260-usart";
> > >
> > > Are the usart blocks in lan966x 1:1 compatible with what is is 
> > > sam9260?
> > > In
> > > case not it may worth to have a new compatible here, for lan966x, 
> > > such
> > > that
> > > when new features will be implemented in usart driver for lan966x the
> > > old
> > > DT (this one) will work with the new kernel implementation.
> >
> > During my review of the inital dtsi patch, I've asked the same 
> > question
> > [1]
> > and I was told they are the same.
> >
> > At least this exact usart compatible is already in this file. I was
> > under
> > the impression, that was the least controversial compatible :)
>
> OK.
>
> > But you'll need to tell me if they are the same or not, I don't have
> > any clue what microchip has reused.
>
> From software point of view comparing registers should be good, as far 
> as I
> can tell. All AT91 datasheet should be available. I though you have 
> checked
> one against LAN966. At the moment I don't have a DS for LAN966. I'll 
> find
> one and have a look.

So my train of thought was like: even if the registers are the same I
cannot be sure that it is the exact same IP and will behave the same.
Therefore, it is something only microchip can answer.

You can find the registers at
https://microchip-ung.github.io/lan9668_reginfo/reginfo_LAN9668.html

I'm not aware of any "classic" datasheet.

-michael