[PATCH 2/2 v2] dma: ipu_idmac: do not lose valid received data in the irq handler

[Guennadi Liakhovetski]

On Sat, 5 Feb 2011, Anatolij Gustschin wrote:

> Hi Guennadi,
> 
> On Thu, 3 Feb 2011 11:09:54 +0100 (CET)
> Guennadi Liakhovetski <g.liakhovetski at gmx.de> wrote:
> 
> > Hi Anatolij
> > 
> > On Mon, 31 Jan 2011, Anatolij Gustschin wrote:
> > 
> > I'm afraid there seems to be a problem with your patch. I have no idea 
> > what is causing it, but I'm just observing some wrong behaviour, that is 
> > not there without it. Namely, I added a debug print to the IDMAC interrupt 
> > handler
> > 
> >  	curbuf	= idmac_read_ipureg(&ipu_data, IPU_CHA_CUR_BUF);
> >  	err	= idmac_read_ipureg(&ipu_data, IPU_INT_STAT_4);
> >  
> > +	printk(KERN_DEBUG "%s(): IDMAC irq %d, buf %d, current %d\n", __func__,
> > +	       irq, ichan->active_buffer, (curbuf >> chan_id) & 1);
> >  
> >  	if (err & (1 << chan_id)) {
> >  		idmac_write_ipureg(&ipu_data, 1 << chan_id, IPU_INT_STAT_4);
> > 
> > and without your patch I see buffer numbers correctly toggling all the 
> > time like
> > 
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 1
> > idmac_interrupt(): IDMAC irq 177, buf 1, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 1
> > idmac_interrupt(): IDMAC irq 177, buf 1, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 1
> > ...
> > 
> > Yes, the first interrupt is different, that's where I'm dropping / 
> > postponing it. With your patch only N (equal to the number of buffers 
> > used, I think) first interrupts toggle, then always only one buffer is 
> > used:
> > 
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> > ...
> > 
> > Verified with both capture.c and mplayer. Could you, please, verify 
> > whether you get the same behaviour and what the problem could be?
> 
> Now I did some further testing with idmac patch applied and with
> added debug print in the IDMAC interrupt handler. There is no problem.
> Testing with capture.c (4 buffers used as default) shows that buffer
> numbers toggle correctly for all 100 captured frames:

Hm, interesting, I'll have to look at my testing in more detail then 
(once back from FOSDEM). Could you maybe try mplayer too?

Thanks
Guennadi

> ...
> mx3-camera mx3-camera.0: MX3 Camera driver attached to camera 0
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> ...
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> mx3-camera mx3-camera.0: MX3 Camera driver detached from camera 0
> 
> Also testing with my test application didn't show any problem.
> When using more than 1 buffer (tested with 2, 3 and 4 queued
> buffers) double buffering works as expected and frame numbers
> toggle correctly. Capturing 30 frames produce:
> 
> mx3-camera mx3-camera.0: MX3 Camera driver attached to camera 0
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> idmac_interrupt(): IDMAC irq 177, buf 0, current 0
> idmac_interrupt(): IDMAC irq 177, buf 1, current 1
> mx3-camera mx3-camera.0: MX3 Camera driver detached from camera 0
> 
> Anatolij
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/