Re: [PATCH] [Streak] Add workaround for TTY kernel OOPS at the cost of performance.

[Tomasz Sterna <tomek@xiaoka.com>]

On czw, 2010-09-30 at 16:04 -0700, Daniel Walker wrote: 
> > Signed-off-by: Bradley Smith <brad@brad-smith.co.uk>
> > (cherry picked from commit 28d06a6366c851c6e0c5b954353bf82cb641d4e7)
> 
> Your submitting this for Bradley? If so you need to have a line like
> this at the top,

I am not exactly _submitting_ it. Bradley said this is a dirty
workaround and needs a real fix instead. This change just gave us
working kernel console.
I am rather pointing the problem and sharing the workaround.


> From: Bradley Smith <brad@brad-smith.co.uk>
> That denotes that your not the author of the commit..

I'm pretty new to git - sorry.
Yes, Bradley is the author of the patch. I only ported it to msm-2.6.35
from his android-msm-2.6.32 tree.

> Also this is against v2.6.36-rcX right ?

This is against msm-2.6.35 
> > +config MSM_FB_TTY_WORKAROUND
> > +	bool "Workaround TTY kernel OOPS at the cost of performance"
> > +	depends on FB_MSM
> > +	default n
> 
> We can't have this selectable , especially if the kernel will OOPS if
> it's off ..

As I mentioned - this is only a workaround of the problem. We turn it on
while debugging kernel boot, and off once it is working to get a better
performing fbcon for X11.


> I need a better description of the problem. What was the oops? This
> looks DMA related, is that accurate and could you expand on why DMA was
> causing a problem?

If you start an android-msm-2.6.29 or msm-2.6.35 (these are the ones I
tested) with MSM_FB driver compiled in and use 'console=tty' kernel
commandline option, kernel starts with proper console output on screen
and oopses in the middle of the process.
I don't know the exact nature of the problem. Maybe Brad would shed some
light.

If you're unable to reproduce the problem, I will rebuild the kernel
without the workaround and retype the OOPS message for you.