linux-kernel - [PATCH v2] ASoC: wm8962: Relax bit clock divider searching

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Date:   Mon,  8 Mar 2021 10:34:37 +0800
From:   Shengjiu Wang <shengjiu.wang@....com>
To:     lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, ckeepax@...nsource.cirrus.com,
        kuninori.morimoto.gx@...esas.com, shengjiu.wang@....com,
        festevam@...il.com, gustavoars@...nel.org,
        sebastian.krzyszkowiak@...i.sm, patches@...nsource.cirrus.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] ASoC: wm8962: Relax bit clock divider searching

With S20_3LE format case, the sysclk = rate * 384,
the bclk = rate * 20 * 2, there is no proper bclk divider
for 384 / 40, because current condition needs exact match.
So driver fails to configure the clocking:

wm8962 3-001a: Unsupported BCLK ratio 9

Fix this by relaxing bitclk divider searching, so that when
no exact value can be derived from sysclk pick the closest
value greater than expected bitclk.

Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
Reviewed-by: Daniel Baluta <daniel.baluta@....com>
---
changes in v2:
- Add debug message according to Charles's comments

 sound/soc/codecs/wm8962.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/sound/soc/codecs/wm8962.c b/sound/soc/codecs/wm8962.c
index ce4666a74793..34080f497584 100644
--- a/sound/soc/codecs/wm8962.c
+++ b/sound/soc/codecs/wm8962.c
@@ -2403,6 +2403,7 @@ static const int sysclk_rates[] = {
 static void wm8962_configure_bclk(struct snd_soc_component *component)
 {
 	struct wm8962_priv *wm8962 = snd_soc_component_get_drvdata(component);
+	int best, min_diff, diff;
 	int dspclk, i;
 	int clocking2 = 0;
 	int clocking4 = 0;
@@ -2473,23 +2474,25 @@ static void wm8962_configure_bclk(struct snd_soc_component *component)
 
 	dev_dbg(component->dev, "DSPCLK is %dHz, BCLK %d\n", dspclk, wm8962->bclk);
 
-	/* We're expecting an exact match */
+	/* Search a proper bclk, not exact match. */
+	best = 0;
+	min_diff = INT_MAX;
 	for (i = 0; i < ARRAY_SIZE(bclk_divs); i++) {
 		if (bclk_divs[i] < 0)
 			continue;
 
-		if (dspclk / bclk_divs[i] == wm8962->bclk) {
-			dev_dbg(component->dev, "Selected BCLK_DIV %d for %dHz\n",
-				bclk_divs[i], wm8962->bclk);
-			clocking2 |= i;
+		diff = (dspclk / bclk_divs[i]) - wm8962->bclk;
+		if (diff < 0) /* Table is sorted */
 			break;
+		if (diff < min_diff) {
+			best = i;
+			min_diff = diff;
 		}
 	}
-	if (i == ARRAY_SIZE(bclk_divs)) {
-		dev_err(component->dev, "Unsupported BCLK ratio %d\n",
-			dspclk / wm8962->bclk);
-		return;
-	}
+	wm8962->bclk = dspclk / bclk_divs[best];
+	clocking2 |= best;
+	dev_dbg(component->dev, "Selected BCLK_DIV %d for %dHz\n",
+		bclk_divs[best], wm8962->bclk);
 
 	aif2 |= wm8962->bclk / wm8962->lrclk;
 	dev_dbg(component->dev, "Selected LRCLK divisor %d for %dHz\n",
-- 
2.27.0