linux-kernel - [PATCH v2 13/17] ASoC: sun8i-codec: Require an exact BCLK divisor match

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Message-Id: <20201014061941.4306-14-samuel@sholland.org>
Date:   Wed, 14 Oct 2020 01:19:37 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>
Cc:     Ondrej Jirman <megous@...ous.com>, alsa-devel@...a-project.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Samuel Holland <samuel@...lland.org>
Subject: [PATCH v2 13/17] ASoC: sun8i-codec: Require an exact BCLK divisor match

Now that we guarantee that SYSCLK is running at the optimal rate when
hw_params succeeds, and that it will continue running at that rate,
SYSCLK will always be an integer multiple of BCLK. So we can always
pick the exact divider, not just the closest divider.

Acked-by: Maxime Ripard <mripard@...nel.org>
Signed-off-by: Samuel Holland <samuel@...lland.org>
---
 sound/soc/sunxi/sun8i-codec.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/sound/soc/sunxi/sun8i-codec.c b/sound/soc/sunxi/sun8i-codec.c
index 253857e66f6f..a530e58018b7 100644
--- a/sound/soc/sunxi/sun8i-codec.c
+++ b/sound/soc/sunxi/sun8i-codec.c
@@ -384,35 +384,31 @@ static const struct sun8i_codec_clk_div sun8i_codec_bclk_div[] = {
 	{ .div = 32,	.val = 8 },
 	{ .div = 48,	.val = 9 },
 	{ .div = 64,	.val = 10 },
 	{ .div = 96,	.val = 11 },
 	{ .div = 128,	.val = 12 },
 	{ .div = 192,	.val = 13 },
 };
 
-static u8 sun8i_codec_get_bclk_div(unsigned int sysclk_rate,
-				   unsigned int lrck_div_order,
-				   unsigned int sample_rate)
+static int sun8i_codec_get_bclk_div(unsigned int sysclk_rate,
+				    unsigned int lrck_div_order,
+				    unsigned int sample_rate)
 {
 	unsigned int div = sysclk_rate / sample_rate >> lrck_div_order;
-	unsigned int best_val = 0, best_diff = ~0;
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(sun8i_codec_bclk_div); i++) {
 		const struct sun8i_codec_clk_div *bdiv = &sun8i_codec_bclk_div[i];
-		unsigned int diff = abs(bdiv->div - div);
 
-		if (diff < best_diff) {
-			best_diff = diff;
-			best_val = bdiv->val;
-		}
+		if (bdiv->div == div)
+			return bdiv->val;
 	}
 
-	return best_val;
+	return -EINVAL;
 }
 
 static int sun8i_codec_get_lrck_div_order(unsigned int slots,
 					  unsigned int slot_width)
 {
 	unsigned int div = slots * slot_width;
 
 	if (div < 16 || div > 256)
@@ -431,18 +427,17 @@ static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
 				 struct snd_soc_dai *dai)
 {
 	struct sun8i_codec *scodec = snd_soc_dai_get_drvdata(dai);
 	struct sun8i_codec_aif *aif = &scodec->aifs[dai->id];
 	unsigned int sample_rate = params_rate(params);
 	unsigned int slots = aif->slots ?: params_channels(params);
 	unsigned int slot_width = aif->slot_width ?: params_width(params);
 	unsigned int sysclk_rate = sun8i_codec_get_sysclk_rate(sample_rate);
-	int lrck_div_order, ret, word_size;
-	u8 bclk_div;
+	int bclk_div, lrck_div_order, ret, word_size;
 
 	/* word size */
 	switch (params_width(params)) {
 	case 8:
 		word_size = 0x0;
 		break;
 	case 16:
 		word_size = 0x1;
@@ -467,16 +462,19 @@ static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
 		return lrck_div_order;
 
 	regmap_update_bits(scodec->regmap, SUN8I_AIF1CLK_CTRL,
 			   SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV_MASK,
 			   (lrck_div_order - 4) << SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV);
 
 	/* BCLK divider (SYSCLK/BCLK ratio) */
 	bclk_div = sun8i_codec_get_bclk_div(sysclk_rate, lrck_div_order, sample_rate);
+	if (bclk_div < 0)
+		return bclk_div;
+
 	regmap_update_bits(scodec->regmap, SUN8I_AIF1CLK_CTRL,
 			   SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV_MASK,
 			   bclk_div << SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV);
 
 	/*
 	 * SYSCLK rate
 	 *
 	 * Clock rate protection is reference counted; but hw_params may be
-- 
2.26.2