[alsa-devel] [PATCH 4/4] ALSA: hdspm - Enable 32 samples/period on RME RayDAT/AIO

[Takashi Iwai]

At Fri, 12 Aug 2011 21:57:49 +0200,
Adrian Knoth wrote:
> 
> Newer RME cards like RayDAT and AIO support 32 samples per period. This
> value is encoded as {1,1,1} in the HDSP_LatencyMask bits in the control
> register.
> 
> Since {1,1,1} is also the representation for 8192 samples/period on
> older RME cards, we have to special case 32 samples and 32768 bytes
> according to the actual card.

IMO, it'd be better to change hdspm_decode_latency() instead.
Otherwise similar corrections are needed in proc read functions.


thanks,

Takashi

> 
> Signed-off-by: Adrian Knoth <adi at drcomp.erfurt.thur.de>
> 
> diff --git a/sound/pci/rme9652/hdspm.c b/sound/pci/rme9652/hdspm.c
> index 159133a..1ed4ba6 100644
> --- a/sound/pci/rme9652/hdspm.c
> +++ b/sound/pci/rme9652/hdspm.c
> @@ -1245,6 +1245,23 @@ static int hdspm_external_sample_rate(struct hdspm *hdspm)
>  static inline void hdspm_compute_period_size(struct hdspm *hdspm)
>  {
>  	hdspm->period_bytes = 1 << ((hdspm_decode_latency(hdspm->control_register) + 8));
> +	if (32768 == hdspm->period_bytes) {
> +		/* Special case for new RME cards with 32 samples period size.
> +		 * The three latency bits in the control register
> +		 * (HDSP_LatencyMask) encode latency values of 64 samples as
> +		 * 0, 128 samples as 1 ... 4096 samples as 6. For old cards, 7
> +		 * denotes 8192 samples, but on new cards like RayDAT or AIO,
> +		 * it corresponds to 32 samples. Multiplied by 4 bytes equals
> +		 * 128 bytes.
> +		 *
> +		 * Note that hdspm->period_bytes isn't used for anything
> +		 * useful on new cards (it's used on old cards in
> +		 * hdspm_hw_pointer), but for the sake of correctness and
> +		 * potential future output via procfs, let's get it right.
> +		 */
> +		if (RayDAT == hdspm->io_type || AIO == hdspm->io_type)
> +			hdspm->period_bytes = 128;
> +	}
>  }
>  
>  
> @@ -1303,12 +1320,27 @@ static int hdspm_set_interrupt_interval(struct hdspm *s, unsigned int frames)
>  
>  	spin_lock_irq(&s->lock);
>  
> -	frames >>= 7;
> -	n = 0;
> -	while (frames) {
> -		n++;
> -		frames >>= 1;
> +	if (32 == frames) {
> +		/* Special case for new RME cards like RayDAT/AIO which
> +		 * support period sizes of 32 samples. Since latency is
> +		 * encoded in the three bits of HDSP_LatencyMask, we can only
> +		 * have values from 0 .. 7. While 0 still means 64 samples and
> +		 * 6 represents 4096 samples on all cards, 7 represents 8192
> +		 * on older cards and 32 samples on new cards.
> +		 *
> +		 * In other words, period size in samples is calculated by
> +		 * 2^(n+6) with n ranging from 0 .. 7.
> +		 */
> +		n = 7;
> +	} else {
> +		frames >>= 7;
> +		n = 0;
> +		while (frames) {
> +			n++;
> +			frames >>= 1;
> +		}
>  	}
> +
>  	s->control_register &= ~HDSPM_LatencyMask;
>  	s->control_register |= hdspm_encode_latency(n);
>  
> -- 
> 1.7.5.4
>