bcm2835-i2s: add 24bit support, update bclk_ratio to more correct values

Original commits:
commit 62c05a0
Author: Florian Meier <[email protected]>
Date:   Fri Dec 6 18:55:53 2013 +0100
    ASoC: BCM2708: Add 24 bit support

commit 3e8c672
Author: popcornmix <[email protected]>
Date:   Sat Sep 13 10:52:04 2014 +0100
    bcm2708-i2s: Update bclk_ratio to more correct values

Discussion about blck_ratio affecting sound quality:
raspberrypi#681

Author: HiassofT

sound/soc/bcm/bcm2835-i2s.c

@@ -340,11 +340,15 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
 	switch (params_format(params)) {
 	case SNDRV_PCM_FORMAT_S16_LE:
 		data_length = 16;
-		bclk_ratio = 40;
+		bclk_ratio = 50;
+		break;
+	case SNDRV_PCM_FORMAT_S24_LE:
+		data_length = 24;
+		bclk_ratio = 50;
 		break;
 	case SNDRV_PCM_FORMAT_S32_LE:
 		data_length = 32;
-		bclk_ratio = 80;
+		bclk_ratio = 100;
 		break;
 	default:
 		return -EINVAL;
@@ -420,7 +424,7 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
 	/* Setup the frame format */
 	format = BCM2835_I2S_CHEN;
 
-	if (data_length > 24)
+	if (data_length >= 24)
 		format |= BCM2835_I2S_CHWEX;
 
 	format |= BCM2835_I2S_CHWID((data_length-8)&0xf);
@@ -711,13 +715,15 @@ static struct snd_soc_dai_driver bcm2835_i2s_dai = {
 		.channels_max = 2,
 		.rates =	SNDRV_PCM_RATE_8000_192000,
 		.formats =	SNDRV_PCM_FMTBIT_S16_LE
+				| SNDRV_PCM_FMTBIT_S24_LE
 				| SNDRV_PCM_FMTBIT_S32_LE
 		},
 	.capture = {
 		.channels_min = 2,
 		.channels_max = 2,
 		.rates =	SNDRV_PCM_RATE_8000_192000,
 		.formats =	SNDRV_PCM_FMTBIT_S16_LE
+				| SNDRV_PCM_FMTBIT_S24_LE
 				| SNDRV_PCM_FMTBIT_S32_LE
 		},
 	.ops = &bcm2835_i2s_dai_ops,