Re: [patch] radeonfb: FB_WAITFORVSYNC implementation

["Ville Syrjälä" <syrjala@sci.fi>]

On Wed, Mar 16, 2005 at 01:28:50AM +0000, Torgeir Veimo wrote:
> On Sat, 2005-03-12 at 17:13 +0200, Ville Syrjälä wrote:
> > On Sat, Mar 12, 2005 at 02:06:45PM +0000, Torgeir Veimo wrote:
> > > This is an implementation of the FB_WAITFORVSYNC ioctl for the radeonfb.
> > > A small test application is attached at the end. This patch is against
> > > vanilla 2.6.11.
> 
> > > +		/* clear interrupt */
> > > +		//OUTREG(GEN_INT_CNTL, int_cntl | CRTC_VBLANK_STAT_ACK);
> > 
> > Why is this commented out?
> 
> Well, first of all is it really important to clear the interrupt when
> enabling it?

Well, this being the vblank interrupt it's not really critical but 
probably a good idea anyway.

> >From what I've seen the rage128 acknowledges an interrupt by writing to
> the int_cntl register, while the radeon does it by writing to the
> int_status register, so I think the above code is not correct.. I might
> want to clear any vblank interrupts by writing to the int_status
> register though.

mach64 chips both enable and ack interrupts using the INT_CNTL register 
(hence the spinlock in atyfb). Apparently they weren't really thinking 
straight when they designed it.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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