[PATCH rtems-libbsd] freebsd/cgem: Use SGMII when necessary

[Kinsey Moore]

On Tue, Nov 1, 2022 at 9:22 PM Chris Johns <chrisj at rtems.org> wrote:

>
>
> On 2/11/2022 1:18 pm, Kinsey Moore wrote:
> > On Tue, Nov 1, 2022 at 5:49 PM Chris Johns <chrisj at rtems.org
> > <mailto:chrisj at rtems.org>> wrote:
> >
> >     On 2/11/2022 8:56 am, Kinsey Moore wrote:
> >     > On Tue, Nov 1, 2022 at 4:14 PM Chris Johns <chrisj at rtems.org
> >     <mailto:chrisj at rtems.org>
> >     > <mailto:chrisj at rtems.org <mailto:chrisj at rtems.org>>> wrote:
> >     >     On 2/11/2022 5:51 am, Kinsey Moore wrote:
> >     >     > Certain hardware configurations will always use SGMII
> instead of RGMII.
> >     >     > Apply the appropriate flags for the relevant BSPs.
> >     >     > ---
> >     >     >  freebsd/sys/dev/cadence/if_cgem.c | 10 ++++++++++
> >     >     >  1 file changed, 10 insertions(+)
> >     >     >
> >     >     > diff --git a/freebsd/sys/dev/cadence/if_cgem.c
> >     >     b/freebsd/sys/dev/cadence/if_cgem.c
> >     >     > index 3eaaf6b2..9b4cf693 100644
> >     >     > --- a/freebsd/sys/dev/cadence/if_cgem.c
> >     >     > +++ b/freebsd/sys/dev/cadence/if_cgem.c
> >     >     > @@ -1296,6 +1296,16 @@ cgem_config(struct cgem_softc *sc)
> >     >     >               CGEM_NET_CFG_FULL_DUPLEX |
> >     >     >               CGEM_NET_CFG_SPEED100;
> >     >     >
> >     >     > +#ifdef __rtems__
> >     >     > +#define STRINGIFY(to_str) #to_str
> >     >     > +#define BSP_STR(to_str) STRINGIFY(to_str)
> >     >     > +     /* Configure the PHYs to use SGMII for particular BSPs
> */
> >     >     > +     if ( 0 == strcmp( BSP_STR(RTEMS_BSP),
> >     "xilinx_zynqmp_lp64_cfc400x" ) ) {
> >     >     > +             net_cfg |= CGEM_NET_CFG_SGMII_EN;
> >     >     > +             net_cfg |= CGEM_NET_CFG_PCS_SEL;
> >     >     > +     }
> >     >
> >     >     This makes it a precedent a cgem device has to be an RTEMS BSP
> to
> >     support SGMII.
> >     >     I do not think that is a good idea.
> >     >
> >     > I don't particularly like this solution either, but I evaluated a
> few other
> >     > options (see below).
> >
> >     I also do not like it.
> >
> >     >     Is the simplest solution adding a weak function call asks
> which mode
> >     and the
> >     >     default call returns RGMII?
> >     >
> >     > The downside to that is that none of the tests can operate as
> expected on a
> >     > SGMII-attached-PHY system since the application would be
> overriding the weak
> >     > symbol and the tests wouldn't do that. Another option would be to
> have a
> >     generic
> >     > option in RTEMS that specifies the PHY attachment and can be set in
> >     config.ini,
> >     > but that would appear to be dead code since it's not used within
> RTEMS.
> >
> >     Would FDT solve this problem? Forcing FDT support onto the cgem
> driver would
> >     break compatibility so it would have to handle a default state. If
> FDT probes
> >     were tolerant of calls without a valid FDT being loaded it would be
> better but
> >     our FDT support seems to have no middle ground from what I can see.
> >
> >
> > FDT could technically solve the problem, current driver support and PHY
> > transport option support notwithstanding. As you pointed out, there isn't
> > currently a way to have both static configuration and FDT support at the
> same
> > time and multiple BSPs across multiple architectures use the CGEM
> support - at
> > least Zynq, ZynqMP, and Versal - all of which would need the appropriate
> support
> > added. I thought we had a RISC-V BSP that used it as well, but I don't
> see it at
> > the moment.
> >
> >
> >     > As far as I'm aware, the closest analog in LibBSD would be the
> buildset
> >     > configuration, but that seems more like a place to define which
> modules get
> >     > built than a location for configuring hardware.
> >
> >     I think FDT is handling this stuff for other archs and the MRMAC
> will also
> >     require FDT support.
> >
> >
> > It is and the FDT support in this driver in FreeBSD 13 is a bit better.
>
> Does this mean existing Zynq etc BSPs would need to add FDT support?
>

Yes, unless there's a solution that allows both to exist at the same time.
I haven't investigated that option thoroughly.

Kinsey
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