Re: [PATCH 5/6 v2] sound: Add n64 driver

Lauri Kasanen
2021-01-10T17:04:05Z

On Sun, 10 Jan 2021 11:24:22 +0100
Takashi Iwai <tiwai@suse.de> wrote:

> > At first there was no nextpos, and _pointer() always reported pos. This
> > didn't work, the core played through the audio at chipmunk speed. So
> > there must be more that I don't understand here.
>
> Try to set the periods_min=2 and the integer periods hw constraint at
> first, and change the pointer callback to return nextpos. Also, at
> the push function, set runtime->delay = period_size as well.

When I do all this, it still causes the chipmunk speed. Several seconds
of audio gets played in 0.3s or so. Sorry if this is taking too much of
your time, I'm a bit lost here at what the alsa core is expecting.

Printks show the following repeats:
start, period size 1024
push, bool irq=0
irq fired
push, bool irq=1
pointer at 8192
stop

It stops and starts again for some reason. This does not happen in the
current pos/nextpos implementation.

> > - the DMA unit has errata if (start + len) & 0x3fff == 0x2000, this
> > must never happen
>
> Ditto.

Can it really handle a constraint this complex? That'd be impressive.
It'd remove the memcpy need if so.

> > - the audio IRQ is not a timer, it fires when the card's internal
> > buffers are empty and need immediate refill
>
> It's the current implementation, right?

Yes, but I was wondering if a different setup would work better. The
alsa setup is a bit confusing to me still.

- Lauri