[U-Boot] [PATCH v2] serial: ns16550: Add register shift variable

[Alexey Brodkin]

Hi Felix,

> -----Original Message-----
> From: Felix Brack [mailto:fb at ltec.ch]
> Sent: Tuesday, July 17, 2018 3:13 PM
> To: Alexander Graf <agraf at suse.de>; Lokesh Vutla <lokeshvutla at ti.com>; u-boot at lists.denx.de
> Cc: Wolfgang Denk <wd at denx.de>; Tom Rini <trini at konsulko.com>; Marek Vasut <marek.vasut at gmail.com>; Patrice Chotard
> <patrice.chotard at st.com>; Michal Simek <michal.simek at xilinx.com>; Simon Glass <sjg at chromium.org>; Alexey Brodkin
> <Alexey.Brodkin at synopsys.com>; Bin Meng <bmeng.cn at gmail.com>; Ley Foon Tan <ley.foon.tan at intel.com>; Patrick Delaunay
> <patrick.delaunay at st.com>; Mario Six <mario.six at gdsys.cc>; Stefan Roese <sr at denx.de>; Bernhard Messerklinger
> <bernhard.messerklinger at br-automation.com>
> Subject: Re: [PATCH v2] serial: ns16550: Add register shift variable

[snip]
 
> Adding a separate PORT in ns16550_serial_ids for a particular
> architecture, platform or SoC would be an option. However the patch I
> posted is much more generic as it offers to set the reg-shift property
> for no matter what architecture, platform or SoC. It can also easily be
> extended by adding more conditional defaults to the Kconfig file.

I'd say we're dealing with just one corner-case here.
If I understand a concept of Device Tree it is supposed to describe your
hardware. Thus if reg shift exists in your HW it should be explicitly mentioned in
your .dts. If for some [historical] reason you have to deal with "incorrect" .dts then
I'd prefer to have mentioned quirk with a separate PORT in ns16550_serial_ids
instead of adding yet another Kconfig option.

Again if OMAP UART is just another flavor of standard 16550 serial port maybe
it's a good idea to convert Linux's "drivers/tty/serial/omap-serial.c" to something
like "drivers/tty/serial/8250/8250_omap.c" with simultaneous fix of .dtsi?

-Alexey