Re: [GIT PULL 1/2] arm64: TI K3 SoC configs changes for v5.17

On Tue, Dec 21, 2021 at 04:55:48PM +0100, Arnd Bergmann wrote:

On Tue, Dec 21, 2021 at 4:32 PM Tom Rini [off-list ref] wrote:

quoted

On Mon, Dec 20, 2021 at 11:10:25PM +0530, Vignesh Raghavendra wrote:

quoted

Currently its not possible to build PCIE_CADENCE_PLAT_HOST/EP drivers as
modules (symbols are bool only).
PCIe is not necessary for basic boot either. So, I can drop these
configs until these drivers are build able as modules, if you prefer.

Is PCIe required for basic boot for the other platforms in the defconfig
which do enable it in the defconfig today?  It is required for non-basic
boot (whatever storage one puts in a PCIe slot).  If someone is going to
be fixing the PCIe driver to be able to be modular, that's fine too but
I ran in to this trying to see what works out of the box in the
defconfig, on this platform and hit both of these rather large
omissions.

If PCI is often used for storage, then that's ok. There are a number of
other platforms where PCIe is only used for wireless networking or
other secondary devices, but they are still built-in because they got
added before it became possible for PCIe host drivers to be loadable
modules. I would like to eventually go through and turn those into
loadable modules, but for the moment it would be good to only add
built-in drivers where this is actually useful.

That's good to know.  My question tho is, what's actually useful?  The
EVM is 2 PCIe x8 type slots.  I honestly don't know if that means "super
useful, arbitrary devices are expected to work" or "not useful,
arbitrary devices are not expected to work".  Is the functional
definition of what's in the defconfig vs left up to users,
distributions, etc, to find and enabled defined, or at least well known
/ explained somewhere?  Where I'm coming from on this is that these
platforms practically are, and can be SystemReady IR certified.  So
what's needed here to ensure there's a good experience distros to enable
what needs enabling for full functionality?  What we hit was "lets throw
some stuff at this board to test it out and.. wait, PCIe isn't enabled
at all? USB host isn't enabled at all?"

And all that said, if someone is going to be fixing the PCIe drivers to
be enabled as modules soon, and just getting it handled that way in the
next appropriately timed merge window, OK, fine, good enough.

-- 
Tom