[alsa-devel] [PATCH 1/2] ASoC: mxs-saif: fix setting master base rate

[Jörg Krause]

From: Jörg Krause <jk at lintech.de>

The SAIF base oversample rates are either 512*fs or 384*fs. An additional
divider exists within the SAIF to generate sub-multiples of these two base
rates if MCLK is required by the codec.

 * The sub-rates for the 512x base rate are: 256x, 128x, 64x, and 32x.
 * The sub-rates for the 384x base rate are: 192x, 96x, and 48x.

Setting the base rate depending on the modulo operation with 32 and 48
give wrong results for some mclk.

If mclk=18.432MHz both modulo operations results in 0. As testing the
result with 32 is done first, a wrong base rate of 512*fs is set instead
of the correct 384*fs.

Fix this by setting the base rate depending on the calculated sub-rate.

Signed-off-by: Jörg Krause <joerg.krause at embedded.rocks>
---
 sound/soc/mxs/mxs-saif.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/sound/soc/mxs/mxs-saif.c b/sound/soc/mxs/mxs-saif.c
index 13631003cb7c..1e724533dc6e 100644
--- a/sound/soc/mxs/mxs-saif.c
+++ b/sound/soc/mxs/mxs-saif.c
@@ -119,23 +119,33 @@ static int mxs_saif_set_clk(struct mxs_saif *saif,
 	 * Set SAIF clock
 	 *
 	 * The SAIF clock should be either 384*fs or 512*fs.
-	 * If MCLK is used, the SAIF clk ratio need to match mclk ratio.
-	 *  For 32x mclk, set saif clk as 512*fs.
-	 *  For 48x mclk, set saif clk as 384*fs.
+	 * If MCLK is used, the SAIF clk ratio needs to match mclk ratio.
+	 *  For 256x, 128x, 64x, and 32x sub-rates, set saif clk as 512*fs.
+	 *  For 192x, 96x, and 48x sub-rates, set saif clk as 384*fs.
 	 *
 	 * If MCLK is not used, we just set saif clk to 512*fs.
 	 */
 	clk_prepare_enable(master_saif->clk);
 
 	if (master_saif->mclk_in_use) {
-		if (mclk % 32 == 0) {
+		switch (mclk / rate) {
+		case 32:
+		case 64:
+		case 128:
+		case 256:
+		case 512:
 			scr &= ~BM_SAIF_CTRL_BITCLK_BASE_RATE;
 			ret = clk_set_rate(master_saif->clk, 512 * rate);
-		} else if (mclk % 48 == 0) {
+			break;
+		case 48:
+		case 96:
+		case 192:
+		case 384:
 			scr |= BM_SAIF_CTRL_BITCLK_BASE_RATE;
 			ret = clk_set_rate(master_saif->clk, 384 * rate);
-		} else {
-			/* SAIF MCLK should be either 32x or 48x */
+			break;
+		default:
+			/* SAIF MCLK should be a sub-rate of 512x or 384x */
 			clk_disable_unprepare(master_saif->clk);
 			return -EINVAL;
 		}
-- 
2.11.0