Re: [RFC PATCH] ARM: omap2plus_defconfig: Switch over to using 8250 driver

[Nishanth Menon <nm@ti.com>]

On 04/10/2015 02:40 PM, Peter Hurley wrote:
> [ +Sebastian, +Tony ]
> 
> On 04/10/2015 02:18 PM, Nishanth Menon wrote:
>> 8250 driver should be relatively feature complete. It can co-exist
>> with omap-serial driver
> 
> Not really; if the omap_8250 is selected then it is probed first
> and will be the only driver claiming omap UART ports.
> 
> omap-serial would just be dead-weight.

true.. my bad..

> 
>> , so just enable 8250 OMAP layer driver and
>> route all ttyOx references to ttySx through the standard 8250 driver
>> to ensure no breakage of userspace occurs.
> 
> Not quite; the only automatic handling is for console only, not for
> userspace. Expect lots of userspace breakage.
> 


Yep - overall, looking through individual logs, in my testing, it seems
to work at least for console for all platforms - even though the
filesystems are mostly going bonkers -> older fs did not have the udev
redirection to take care of this - mostly to do with the getty hooked on
to static consoles.


There are infact two issues:
a) bootloader change for cmdline -> O2 to S2 -> in many cases we are
lesser inclined to change the bootloader, hence the fixup configuration
b) fs changes - these are sometimes more realistic to do, but is a clear
breakage risk.


Overall, keeping two equally functional drivers in the system sounds a
bunch of maintenance burden for all of us and not to mention confusion
for the future.


Btw, I am not exactly proposing this for 4.1 kernel.. instead, we should
probably discuss how to best introduce this in and throw out the older
omap_serial driver - just reuse 8250 and co-exist with the rest of the
good world folks ;)..


-- 
Regards,
Nishanth Menon