ASoC: tlv320aic31xx: Add support for loading filter coefficients

The TLV320DAC3100 Audio DAC has 25 built-in digital audio processing blocks
(PRBs). Each of these PRBs has a static filter structure with programmable
coefficients. Once a PRB is selected for use by the DAC, its filter
coefficients can be configured via a dedicated set of registers.

Define a new optional firmware which can be loaded by the TLV320DAC driver.
This firmware describes a full set of filter coefficients for all blocks
used by the various PRBs.

The firmware's binary format is heavily inspired by the one used in the
peb2466 driver. It includes a version marker to allow for potential
evolutions of the format.

Note that adaptive filtering is not supported i.e. filter coefficients are
loaded once before power-on and then cannot be changed while the DAC is
powered. This is why only page A coefficients are modified. Page B
coefficients are only used for adaptive filtering.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Link: https://patch.msgid.link/20240906-tlv320-filter-v1-1-6955f53ff435@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: rgantois

sound/soc/codecs/tlv320aic31xx.c

@@ -12,6 +12,7 @@
  * and mono/stereo Class-D speaker driver.
  */
 
+#include <asm/unaligned.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/init.h>
@@ -22,6 +23,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/regulator/consumer.h>
 #include <linux/acpi.h>
+#include <linux/firmware.h>
 #include <linux/of.h>
 #include <linux/slab.h>
 #include <sound/core.h>
@@ -1638,6 +1640,98 @@ static const struct i2c_device_id aic31xx_i2c_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, aic31xx_i2c_id);
 
+static int tlv320dac3100_fw_load(struct aic31xx_priv *aic31xx,
+				 const u8 *data, size_t size)
+{
+	int ret, reg;
+	u16 val16;
+
+	/*
+	 * Coefficients firmware binary structure. Multi-byte values are big-endian.
+	 *
+	 * @0, 16bits: Magic (0xB30C)
+	 * @2, 16bits: Version (0x0100 for version 1.0)
+	 * @4, 8bits: DAC Processing Block Selection
+	 * @5, 62 16-bit values: Page 8 buffer A DAC programmable filter coefficients
+	 * @129, 12 16-bit values: Page 9 Buffer A DAC programmable filter coefficients
+	 *
+	 * Filter coefficients are interpreted as two's complement values
+	 * ranging from -32 768 to 32 767. For more details on filter coefficients,
+	 * please refer to the TLV320DAC3100 datasheet, tables 6-120 and 6-123.
+	 */
+
+	if (size != 153) {
+		dev_err(aic31xx->dev, "firmware size is %zu, expected 153 bytes\n", size);
+		return -EINVAL;
+	}
+
+	/* Check magic */
+	val16 = get_unaligned_be16(data);
+	if (val16 != 0xb30c) {
+		dev_err(aic31xx->dev, "fw magic is 0x%04x expected 0xb30c\n", val16);
+		return -EINVAL;
+	}
+	data += 2;
+
+	/* Check version */
+	val16 = get_unaligned_be16(data);
+	if (val16 != 0x0100) {
+		dev_err(aic31xx->dev, "invalid firmware version 0x%04x! expected 1", val16);
+		return -EINVAL;
+	}
+	data += 2;
+
+	ret = regmap_write(aic31xx->regmap, AIC31XX_DACPRB, *data);
+	if (ret) {
+		dev_err(aic31xx->dev, "failed to write PRB index: err %d\n", ret);
+		return ret;
+	}
+	data += 1;
+
+	/* Page 8 Buffer A coefficients */
+	for (reg = 2; reg < 126; reg++) {
+		ret = regmap_write(aic31xx->regmap, AIC31XX_REG(8, reg), *data);
+		if (ret) {
+			dev_err(aic31xx->dev,
+				"failed to write page 8 filter coefficient %d: err %d\n", reg, ret);
+			return ret;
+		}
+		data++;
+	}
+
+	/* Page 9 Buffer A coefficients */
+	for (reg = 2; reg < 26; reg++) {
+		ret = regmap_write(aic31xx->regmap, AIC31XX_REG(9, reg), *data);
+		if (ret) {
+			dev_err(aic31xx->dev,
+				"failed to write page 9 filter coefficient %d: err %d\n", reg, ret);
+			return ret;
+		}
+		data++;
+	}
+
+	dev_info(aic31xx->dev, "done loading DAC filter coefficients\n");
+
+	return ret;
+}
+
+static int tlv320dac3100_load_coeffs(struct aic31xx_priv *aic31xx,
+				     const char *fw_name)
+{
+	const struct firmware *fw;
+	int ret;
+
+	ret = request_firmware(&fw, fw_name, aic31xx->dev);
+	if (ret)
+		return ret;
+
+	ret = tlv320dac3100_fw_load(aic31xx, fw->data, fw->size);
+
+	release_firmware(fw);
+
+	return ret;
+}
+
 static int aic31xx_i2c_probe(struct i2c_client *i2c)
 {
 	struct aic31xx_priv *aic31xx;
@@ -1727,6 +1821,12 @@ static int aic31xx_i2c_probe(struct i2c_client *i2c)
 		}
 	}
 
+	if (aic31xx->codec_type == DAC3100) {
+		ret = tlv320dac3100_load_coeffs(aic31xx, "tlv320dac3100-coeffs.bin");
+		if (ret)
+			dev_warn(aic31xx->dev, "Did not load any filter coefficients\n");
+	}
+
 	if (aic31xx->codec_type & DAC31XX_BIT)
 		return devm_snd_soc_register_component(&i2c->dev,
 				&soc_codec_driver_aic31xx,