[alsa-devel] [PATCH] ASoC: atmel_ssc_dai: Match the CMR divider only in full duplex.

[Peter Rosin]

The CMR divider register is shared by playback and capture. The SSC driver
therefore tries to enforce rules so that the needed register content do
not conflict during simultaneous playback/capture. However, the
implementation also prevents changing the register content in
half-duplex scenarios, which is needed when using the OSS API.

Thus, only lock the divider if there is a stream in the other direction.

Fixes the below program to not fail with the atmel ssc dai in master mode.

#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/soundcard.h>

int
main(void)
{
	int fd;
	int format;
	int channels;
	int speed;

	if ((fd = open("/dev/dsp", O_WRONLY, 0)) == -1) {
		perror("open");
		return 1;
	}
	format = AFMT_S16_LE;
	if (ioctl(fd, SNDCTL_DSP_SETFMT, &format) == -1) {
		perror("SNDCTL_DSP_SETFMT");
		return 1;
	}
	channels = 2;
	if (ioctl(fd, SNDCTL_DSP_CHANNELS, &channels) == -1) {
		perror("SNDCTL_DSP_CHANNELS");
		return 1;
	}
	speed = 22025;
	if (ioctl(fd, SNDCTL_DSP_SPEED, &speed) == -1) {
		perror("SNDCTL_DSP_SPEED");
		return 1;
	}
	return 0;
}

Signed-off-by: Peter Rosin <peda at axentia.se>
---
 sound/soc/atmel/atmel_ssc_dai.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
index f403f39..b1cc2a4 100644
--- a/sound/soc/atmel/atmel_ssc_dai.c
+++ b/sound/soc/atmel/atmel_ssc_dai.c
@@ -310,7 +310,10 @@ static int atmel_ssc_set_dai_clkdiv(struct snd_soc_dai *cpu_dai,
 		 * transmit and receive, so if a value has already
 		 * been set, it must match this value.
 		 */
-		if (ssc_p->cmr_div == 0)
+		if (ssc_p->dir_mask !=
+			(SSC_DIR_MASK_PLAYBACK | SSC_DIR_MASK_CAPTURE))
+			ssc_p->cmr_div = div;
+		else if (ssc_p->cmr_div == 0)
 			ssc_p->cmr_div = div;
 		else
 			if (div != ssc_p->cmr_div)
-- 
2.1.1