Various cleanups to the x86 early serial driver, mostly with the goal
of simplifying its deployment during board bringup (which is really
the only reason it exists in the first place):
+ Configure it =y by default. While there are surely constrained
environments that will want to disable it, this is a TINY driver,
and it serves a very important role for niche tasks. It should be
built always to make sure it works everywhere.
+ Decouple from devicetree as much as possible. This code HAS to work
during board bringup, often with configurations cribbed from other
machines, before proper configuration gets written. Experimentally,
devicetree errors tend to be easy to make, and without a working
console impossible to diagnose. Specify the device via integer
constants in soc.h (in the case of IOPORT access, we already had
such a symbol) so that the path from what the developer intends to
what the code executes is as short and obvious as possible.
Unfortunately I'm not allowed to remove devicetree entirely here,
but at least a developer adding a new platform will be able to
override it in an obvious way instead of banging blindly on the
other side of a DTS compiler.
+ Don't try to probe the PCI device by ID to "verify". While this
sounds like a good idea, in practice it's just an extra thing to get
wrong. If we bail on our early console because someone (yes, that's
me) got the bus/device/function right but typoed the VID/DID
numbers, we're doing no one any favors.
+ Remove the word-sized-I/O feature. This is a x86 driver for a PCI
device. No known PC hardware requires that UART register access be
done in dword units (in fact doing so would be a violation of the
PCI specifciation as I understand it). It looks to have been cut
and pasted from the ns16550 driver, remove.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
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