[mpeg2] Re: Fw: Fix for kernel-freezes

[Bram Stolk <b.stolk@chello.nl>]

On Fri, 1 Feb 2002 09:54:29 -0700
Kevin Tsui <ktsui@cdlsystems.com> wrote:

> 	I have tried to look at the "mdelay" operations in kfir.c and found that 
> most of the delay time is around 1 - 10 ms, which I think they are relatively 
> small time slices and wouldn't be noticed by normal users. However, I found 

Yep, 10ms is ofcourse a small amount of time in a user's point of view.
Then again, it's a seemingly endless ten million processor cycles from the
CPU's point of view :-)

> there are 2 major "mdelay" in kfir.c, one is delaying by 100ms, the other is 
> 1000ms (or 1 second). I changed them to 10ms and 100ms respectively and the

Yes, and because ADSP inits fail for me, the large mdelays are used
for numerous retries in my case.
 
> driver still seems to work fine. (In fact, I think these 2 mdelay are only 
> used when loading the micro code)
> 
> 	Anyway, hope this helps.

It does... Be sure to tell us when you find a mdelay that *does* mess up
the kfir functionality.

   thanks,

      Bram


> Kevin.
> 
> > ----- Original Message -----
> > From: "Bram Stolk" <b.stolk@chello.nl>
> > To: <mpeg2@linuxtv.org>
> > Sent: Friday, February 01, 2002 5:05 AM
> > Subject: [mpeg2] Fix for kernel-freezes
> >
> > > hi,
> > >
> > > When using the kfir module, you will have noticed
> > > that the kernel freezes regularly for a few seconds or so.
> > > Most noticably during module load, and during device closing.
> > >
> > > (Try e.g. switching virtual consoles when loading kfir.o:
> > >  it will not work, as ALL system services are halted during
> > >  this time)
> > >
> > > This is because the kernel module issues mdelay operations.
> > > These are evil operations, and should always be avoided if
> > > possible.
> > >
> > > What's worse... it turns out that most of these delays
> > > are not necessary, at least in my setup.
> > >
> > > For instance, when redefining 'Sleep' to return without
> > > delay, has had *no* impact on the functionality of my BMK
> > > mpeg encoder card.
> > >
> > > To improve the responsiveness of the system, I advice you to
> > > redefine Sleep() in kfir.o as:
> > > static inline void Sleep(int i)
> > > {
> > >         return;
> > > }
> > >
> > > Next, I propose a carefull examination of all remaining
> > > mdelay() ops, and see if the can be removed, or else lowered.
> > > This can be a labourous task, so if we divide the workload
> > > among the members of this mailinglist, we can probably
> > > empirically designate those mdelays that are actually needed.
> > >
> > > So... who's with me?
> > >
> > >   Bram
>