[Intel-gfx] [PATCH] drm/i915: Add aub debug support for kernel

[Liu, Yuanhan]

On Tue, 2010-11-02 at 22:55 +0800, Liu Aleaxander wrote:
>
> > Being able to trace the register writes using ftrace is good... In fact we
> > can remove our own printks and just use mmiotrace. So is it possible to
> > post-process mmiotrace into .aub?
> 
> As I found mmiotrace can handle the operation(read or write), the
> register address
> and the value's size, yes, it is(I guess).  I will do more
> investigation tomorrow.
> 
> Hi,

One should do this 'echo mmiotrace > /sys/kernel/debug/tracing' to enable 
mmio trace. And this should be done before calling ioremap function, AKA, 
before loading a module. So, first, user should have to stop i915 modules 
from loading at the boot time. Then enable mmiotrace like said above, then 
modprobe i915 by hand. And yes, all the register data are recorded. But just 
a while, I get a data file about 1G(Since it recorded everything, and some 
register write and read too often).

So, I'm not sure this good for debug. One great advantage of aub file is that 
user can gave an aub file to us, then we may know what was going wrong, 
just like we often ask user for something like dmesg log. As it's a bit hard for 
user to generate an aub file, then it's not good for us to debug.

So, ideas and comments? (And feel free to correct me if I'm wrong)


Thanks!


--
regards
Yuanhan Liu