ALSA: firewire-lib/dice: add arrangements of PCM pointer and interrupts for Dice quirk

In IEC 61883-6, one data block transfers one event. In ALSA, the event equals one PCM frame,
hence one data block transfers one PCM frame. But Dice has a quirk at higher sampling rate
(176.4/192.0 kHz) that one data block transfers two PCM frames.

Commit 10550bea44a8 ("ALSA: dice/firewire-lib: Keep dualwire mode but obsolete
CIP_HI_DUALWIRE") moved some codes related to this quirk into Dice driver. But the commit
forgot to add arrangements for PCM period interrupts and DMA pointer updates. As a result, Dice
driver cannot work correctly at higher sampling rate.

This commit adds 'double_pcm_frames' parameter to amdtp structure for this quirk. When this
parameter is set, PCM period interrupts and DMA pointer updates occur at double speed than in
IEC 61883-6.

Reported-by: Daniel Robbins <drobbins@funtoo.org>
Fixes: 10550bea44a8 ("ALSA: dice/firewire-lib: Keep dualwire mode but obsolete CIP_HI_DUALWIRE")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: <stable@vger.kernel.org> # 3.16
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 11 insertions, 4 deletions

diff --git a/sound/firewire/dice.c b/sound/firewire/dice.c
index 4cf8eb704045..e3a04d69c853 100644
--- a/sound/firewire/dice.c
+++ b/sound/firewire/dice.c
@@ -567,10 +567,14 @@ static int dice_hw_params(struct snd_pcm_substream *substream,
 		return err;
 
 	/*
-	 * At rates above 96 kHz, pretend that the stream runs at half the
-	 * actual sample rate with twice the number of channels; two samples
-	 * of a channel are stored consecutively in the packet. Requires
-	 * blocking mode and PCM buffer size should be aligned to SYT_INTERVAL.
+	 * At 176.4/192.0 kHz, Dice has a quirk to transfer two PCM frames in
+	 * one data block of AMDTP packet. Thus sampling transfer frequency is
+	 * a half of PCM sampling frequency, i.e. PCM frames at 192.0 kHz are
+	 * transferred on AMDTP packets at 96 kHz. Two successive samples of a
+	 * channel are stored consecutively in the packet. This quirk is called
+	 * as 'Dual Wire'.
+	 * For this quirk, blocking mode is required and PCM buffer size should
+	 * be aligned to SYT_INTERVAL.
 	 */
 	channels = params_channels(hw_params);
 	if (rate_index > 4) {
@@ -581,6 +585,9 @@ static int dice_hw_params(struct snd_pcm_substream *substream,
 
 		rate /= 2;
 		channels *= 2;
+		dice->stream.double_pcm_frames = true;
+	} else {
+		dice->stream.double_pcm_frames = false;
 	}
 
 	mode = rate_index_to_mode(rate_index);