openwrt/target/linux/bcm27xx/patches-6.6/950-1029-ASoC-bcm-Use-power-of-2-bclk_ratios.patch

From 18851c5d16707ee628bd771da8822e9402ec7a1a Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 17 Apr 2024 17:20:05 +0100
Subject: [PATCH 1029/1085] ASoC: bcm: Use power-of-2 bclk_ratios

The soundcard drivers originally used snd_pcm_format_physical_width,
but a later commit changed that to snd_pcm_format_width because the
in-memory sample storage width should not be a factor in determining
the bclk_ratio. However, the physical width rounds the sample bits up
to the nearest power of 2, which makes it easier to find integer clock
divisors.

Restore the old behaviour, but with an implementation that makes it
clear what is going on.

See: https://github.com/raspberrypi/linux/issues/6104

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 sound/soc/bcm/allo-boss-dac.c           | 3 +++
 sound/soc/bcm/dionaudio_loco.c          | 3 +++
 sound/soc/bcm/hifiberry_dacplus.c       | 3 +++
 sound/soc/bcm/hifiberry_dacplusadc.c    | 3 +++
 sound/soc/bcm/hifiberry_dacplusadcpro.c | 3 +++
 sound/soc/bcm/i-sabre-q2m.c             | 5 +++--
 sound/soc/bcm/rpi-cirrus.c              | 3 +++
 sound/soc/bcm/rpi-simple-soundcard.c    | 5 ++++-
 8 files changed, 25 insertions(+), 3 deletions(-)

--- a/sound/soc/bcm/allo-boss-dac.c
+++ b/sound/soc/bcm/allo-boss-dac.c
@@ -278,6 +278,9 @@ static int snd_allo_boss_hw_params(
 	struct snd_soc_component *component = asoc_rtd_to_codec(rtd, 0)->component;
 	struct snd_soc_card *card = rtd->card;
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	width = width <= 16 ? 16 : 32;
+
 	/* Mute before changing sample rate */
 	snd_allo_boss_gpio_mute(card);
 
--- a/sound/soc/bcm/dionaudio_loco.c
+++ b/sound/soc/bcm/dionaudio_loco.c
@@ -34,6 +34,9 @@ static int snd_rpi_dionaudio_loco_hw_par
 	unsigned int sample_bits =
 		snd_pcm_format_width(params_format(params));
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	sample_bits = sample_bits <= 16 ? 16 : 32;
+
 	return snd_soc_dai_set_bclk_ratio(cpu_dai, sample_bits * 2);
 }
 
--- a/sound/soc/bcm/hifiberry_dacplus.c
+++ b/sound/soc/bcm/hifiberry_dacplus.c
@@ -297,6 +297,9 @@ static int snd_rpi_hifiberry_dacplus_hw_
 	int channels = params_channels(params);
 	int width = snd_pcm_format_width(params_format(params));
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	width = width <= 16 ? 16 : 32;
+
 	if (snd_rpi_hifiberry_is_dacpro) {
 		struct snd_soc_component *component = asoc_rtd_to_codec(rtd, 0)->component;
 
--- a/sound/soc/bcm/hifiberry_dacplusadc.c
+++ b/sound/soc/bcm/hifiberry_dacplusadc.c
@@ -231,6 +231,9 @@ static int snd_rpi_hifiberry_dacplusadc_
 	int channels = params_channels(params);
 	int width = snd_pcm_format_width(params_format(params));
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	width = width <= 16 ? 16 : 32;
+
 	if (snd_rpi_hifiberry_is_dacpro) {
 		struct snd_soc_component *component = asoc_rtd_to_codec(rtd, 0)->component;
 
--- a/sound/soc/bcm/hifiberry_dacplusadcpro.c
+++ b/sound/soc/bcm/hifiberry_dacplusadcpro.c
@@ -389,6 +389,9 @@ static int snd_rpi_hifiberry_dacplusadcp
 	struct snd_soc_dai_driver *drv = dai->driver;
 	const struct snd_soc_dai_ops *ops = drv->ops;
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	width = width <= 16 ? 16 : 32;
+
 	if (snd_rpi_hifiberry_is_dacpro) {
 		snd_rpi_hifiberry_dacplusadcpro_set_sclk(dac,
 			params_rate(params));
--- a/sound/soc/bcm/i-sabre-q2m.c
+++ b/sound/soc/bcm/i-sabre-q2m.c
@@ -53,8 +53,9 @@ static int snd_rpi_i_sabre_q2m_hw_params
 	struct snd_soc_dai         *cpu_dai = asoc_rtd_to_cpu(rtd, 0);
 	int bclk_ratio;
 
-	bclk_ratio = snd_pcm_format_width(
-			params_format(params)) * params_channels(params);
+	/* Using powers of 2 allows for an integer clock divisor */
+	bclk_ratio = (snd_pcm_format_width(params_format(params)) <= 16 ? 16 : 32) *
+				 params_channels(params);
 	return snd_soc_dai_set_bclk_ratio(cpu_dai, bclk_ratio);
 }
 
--- a/sound/soc/bcm/rpi-cirrus.c
+++ b/sound/soc/bcm/rpi-cirrus.c
@@ -708,6 +708,9 @@ static int rpi_cirrus_hw_params(struct s
 	unsigned int rate = params_rate(params);
 	unsigned int clk_freq = calc_sysclk(rate);
 
+	/* Using powers of 2 allows for an integer clock divisor */
+	width = width <= 16 ? 16 : 32;
+
 	mutex_lock(&priv->lock);
 
 	dev_dbg(card->dev, "hw_params: setting rate to %d\n", rate);
--- a/sound/soc/bcm/rpi-simple-soundcard.c
+++ b/sound/soc/bcm/rpi-simple-soundcard.c
@@ -134,10 +134,13 @@ static int snd_rpi_simple_hw_params(stru
 		return 0; // BCLK is configured in .init
 
 	/* The simple drivers just set the bclk_ratio to sample_bits * 2 so
-	 * hard-code this for now. More complex drivers could just replace
+	 * hard-code this for now, but sticking to powers of 2 to allow for
+	 * integer clock divisors. More complex drivers could just replace
 	 * the hw_params routine.
 	 */
 	sample_bits = snd_pcm_format_width(params_format(params));
+	sample_bits = sample_bits <= 16 ? 16 : 32;
+
 	return snd_soc_dai_set_bclk_ratio(cpu_dai, sample_bits * 2);
 }