Manu Abraham wrote:
>
> >I still don't know what causes the audio fifo to overflow
> >on some chipsets - the video fifo seems to never show
> >this problem (yeah, it's two time as big but the data
> >rate is much more then twice of that comming via DVB).
>
> The reason why it overflows is data is not read from the FIFO as it
> should be and the PCI bus expects larger chunks. Another way of handling
> this is to reduce the latency, [...]
All good and fine - but I get no errors with the video fifo,
only with the audio fifo. Afaics, there are only two differences:
the video fifo is two times as deep as the audio fifo (but data rates
are 4-8 times as high), and the read-only MAX_LAT register which is
10us for video and 64us for audio.
> >-static int bt878_make_risc(struct bt878 *bt)
> >+static int bt878_calc_line_size(struct bt878 *bt)
>
> calc_line_size would be misleading, since it is in fact creating the
> RISC program itself.
No, that's bt878_risc_program. Hence the name change.
> >+ if (astat & ~BT878_ARISCI) {
> >+ if (time_after(jiffies, bt->error_expire))
> >+ bt->errors = 0;
> >+ bt->error_expire = jiffies + 5*HZ;
> >+ bt->errors++;
>
> IMHO, You shouldn't be sleeping inside an interrupt handler.
Heh? Who's sleeping? The expire is there to reset the error
counter if everything was well for 5 seconds. I don't want
to reset dma if there's only a single error every 2 hours.
> >+ if (bt->errors == 10 || bt->errors == 15) {
> >+ printk(KERN_ERR "bt878(%d): too many errors, "
> >+ "resetting dma\n", bt->nr);
> >+ /* reset dma and set fifo-trigger to minimum */
> >+ btand(~0x1f, BT878_AGPIO_DMA_CTL);
> >+ btor(0x13, BT878_AGPIO_DMA_CTL);
> >+ }
> >+ if (bt->errors == 20) {
> >+ printk(KERN_ERR "bt878(%d): too many errors, "
> >+ "shutting up\n", bt->nr);
> >+ btwrite(BT878_ARISCI, BT878_AINT_MASK);
> >+ }
>
> I would say that just,
>
> errors > error_count,
> do_operations would be sufficient ..
No, won't do.
> But anyway what's the idea behind reducing the fifo size if in case of
> errors ? normally when we have communication errors , we generally
> increase the buffer size, not reduce it...
Not the fifo-depth is changed (that's not possible in the bt878), the
trigger point at which access to the PCI bus is requested is lowered.
Ciao, ET.
