On Tue, Sep 29, 2020 at 04:53:47PM +0100, Grant Likely wrote:
>
>
> On 29/09/2020 14:43, Andrew Lunn wrote:
> > On Tue, Sep 29, 2020 at 10:47:03AM +0530, Calvin Johnson wrote:
> > > Hi Grant,
> > >
> > > On Fri, Sep 25, 2020 at 02:34:21PM +0100, Grant Likely wrote:
> > > > > +DSDT entry for MDIO node
> > > > > +------------------------
> > > > > +a) Silicon Component
> > > > > +--------------------
> > > > > + Scope(_SB)
> > > > > + {
> > > > > + Device(MDI0) {
> > > > > + Name(_HID, "NXP0006")
> > > > > + Name(_CCA, 1)
> > > > > + Name(_UID, 0)
> > > > > + Name(_CRS, ResourceTemplate() {
> > > > > + Memory32Fixed(ReadWrite, MDI0_BASE, MDI_LEN)
> > > > > + Interrupt(ResourceConsumer, Level, ActiveHigh, Shared)
> > > > > + {
> > > > > + MDI0_IT
> > > > > + }
> > > > > + }) // end of _CRS for MDI0
> > > > > + Name (_DSD, Package () {
> > > > > + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> > > > > + Package () {
> > > > > + Package () {"little-endian", 1},
> > > > > + }
> > > >
> > > > Adopting the 'little-endian' property here makes little sense. This looks
> > > > like legacy from old PowerPC DT platforms that doesn't belong here. I would
> > > > drop this bit.
> > >
> > > I'm unable to drop this as the xgmac_mdio driver relies on this variable to
> > > change the io access to little-endian. Default is big-endian.
> > > Please see:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/freescale/xgmac_mdio.c?h=v5.9-rc7#n55
> >
> > Hi Calvin
> >
> > Are we talking about the bus controller endiannes, or the CPU
> > endianness?
>
> This is orthogonal to the MDIO bus issue. This is a legacy of the xgmac IP
> block originating in PowerPC platforms with a big-endian bus wiring. The
> flag here tells the driver to use little endian when accessing MMIO
> registers.
>
> > If we are talking about the CPU endiannes, are you plan on supporting
> > any big endian platforms using ACPI? If not, just hard code it.
> > Newbie ACPI question: Does ACPI even support big endian CPUs, given
> > its x86 origins? >
> > If this is the bus controller endianness, are all the SoCs you plan to
> > support via ACPI the same endianness? If they are all the same, you
> > can hard code it.
>
> I would agree. The ACPI and DT probe paths are different. It would be easy
> to automatically set the little-endian flag by default when xgmac is
> described via ACPI.
Thanks Andrew and Grant for this suggestion. Yes, this is an easy way to solve
this problem. Will do that.
Regards
Calvin
