ASoC: atmel_ssc_dai: Match the CMR divider only in full duplex.

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.

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@axentia.se>
Acked-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

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)