[Openvortex-dev] DMA buffer constraints (no more clicks)

[Manuel Jander]

Hello,

Adding the following lines to the "open" callback in au88x0_pcm.c
should eliminate clicks. It prevents wrong period sizes.

Know as i think about it, it semes quite obvious. If a period isnt a
multiple of a frame size, at least one frame gets cut in 2 pieces when
crossing the period boundary. Being a hardware guy, i wouldn't expect
the Aureal chips to reassemble a split frame ;)

This how it should be. I didnt upload it to CVS, because some programs
like aplay just give up on playback if the period size the want can't be
granted. I don't know how to solve that now; thats aplay's fault in my
opinion. 
The ice1724 driver does basically the same (for reference).
Any comments a greatly appreciated.

Best Regards

Manuel Jander.



static int snd_vortex_pcm_open(snd_pcm_substream_t *substream) {
    chip_t *chip = snd_pcm_substream_chip(substream);
    snd_pcm_runtime_t *runtime = substream->runtime;
        int dma, err;
        
        /* Force equal size periods */
        if ((err = snd_pcm_hw_constraint_integer(runtime,
SNDRV_PCM_HW_PARAM_PERIODS)) < 0)
        return err;
        /* Force DMA 32 bit alignment */
        if ((err = snd_pcm_hw_constraint_step(runtime, 0,
SNDRV_PCM_HW_PARAM_PERIOD_BYTES, 4)) < 0)
        return err;
        
    if (substream->pcm == chip->pcm_adb) {
                runtime->hw = snd_vortex_playback_hw_adb;
                dma = vortex_getadb(chip);
                if (dma < 0)
                        return -EBUSY;
                substream->runtime->private_data = &chip->dma_adb[dma];
        chip->dma_adb[dma].substream = substream;
    } else {
                runtime->hw = snd_vortex_playback_hw_wt;
                dma = vortex_getwt(chip);
                if (dma < 0)
                        return -EBUSY;
                substream->runtime->private_data = &chip->dma_wt[dma];
        chip->dma_wt[dma].substream = substream;
    }
    return 0;
}