ASoC: cs35l56: Read firmware uuid from a device property instead of _SUB

Use a device property "cirrus,firmware-uid" to get the unique firmware
identifier instead of using ACPI _SUB. There aren't any products that use
_SUB.

There will not usually be a _SUB in Soundwire nodes. The ACPI can use a
_DSD section for custom properties.

There is also a need to support instantiating this driver using software
nodes. This is for systems where the CS35L56 is a back-end device and the
ACPI refers only to the front-end audio device - there will not be any ACPI
references to CS35L56.

Fixes: e496112 ("ASoC: cs35l56: Add driver for Cirrus Logic CS35L56")
Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230817112712.16637-2-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: mstrozek

sound/soc/codecs/cs35l56.c

@@ -5,7 +5,6 @@
 // Copyright (C) 2023 Cirrus Logic, Inc. and
 //                    Cirrus Logic International Semiconductor Ltd.
 
-#include <linux/acpi.h>
 #include <linux/completion.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
@@ -1354,26 +1353,22 @@ static int cs35l56_dsp_init(struct cs35l56_private *cs35l56)
 	return 0;
 }
 
-static int cs35l56_acpi_get_name(struct cs35l56_private *cs35l56)
+static int cs35l56_get_firmware_uid(struct cs35l56_private *cs35l56)
 {
-	acpi_handle handle = ACPI_HANDLE(cs35l56->dev);
-	const char *sub;
+	struct device *dev = cs35l56->dev;
+	const char *prop;
+	int ret;
 
-	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
-	if (!handle)
+	ret = device_property_read_string(dev, "cirrus,firmware-uid", &prop);
+	/* If bad sw node property, return 0 and fallback to legacy firmware path */
+	if (ret < 0)
 		return 0;
 
-	sub = acpi_get_subsystem_id(handle);
-	if (IS_ERR(sub)) {
-		/* If bad ACPI, return 0 and fallback to legacy firmware path, otherwise fail */
-		if (PTR_ERR(sub) == -ENODATA)
-			return 0;
-		else
-			return PTR_ERR(sub);
-	}
+	cs35l56->dsp.system_name = devm_kstrdup(dev, prop, GFP_KERNEL);
+	if (cs35l56->dsp.system_name == NULL)
+		return -ENOMEM;
 
-	cs35l56->dsp.system_name = sub;
-	dev_dbg(cs35l56->dev, "Subsystem ID: %s\n", cs35l56->dsp.system_name);
+	dev_dbg(dev, "Firmware UID: %s\n", cs35l56->dsp.system_name);
 
 	return 0;
 }
@@ -1417,7 +1412,7 @@ int cs35l56_common_probe(struct cs35l56_private *cs35l56)
 		gpiod_set_value_cansleep(cs35l56->reset_gpio, 1);
 	}
 
-	ret = cs35l56_acpi_get_name(cs35l56);
+	ret = cs35l56_get_firmware_uid(cs35l56);
 	if (ret != 0)
 		goto err;
 
@@ -1604,8 +1599,6 @@ void cs35l56_remove(struct cs35l56_private *cs35l56)
 
 	regcache_cache_only(cs35l56->regmap, true);
 
-	kfree(cs35l56->dsp.system_name);
-
 	gpiod_set_value_cansleep(cs35l56->reset_gpio, 0);
 	regulator_bulk_disable(ARRAY_SIZE(cs35l56->supplies), cs35l56->supplies);
 }