ASoC: cs35l41: Read System Name from ACPI _SUB to identify firmware

When loading firmware, wm_adsp uses a number of parameters to
determine the path of the firmware and tuning files to load.
One of these parameters is system_name.
Add support in cs35l41 to read this system name from the ACPI
_SUB ID in order to uniquely identify the firmware and tuning
mapped to a particular system.
Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220707151037.3901050-3-sbinding@opensource.cirrus.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/cs35l41.c

@@ -6,6 +6,7 @@
 //
 // Author: David Rhodes <david.rhodes@cirrus.com>
 
+#include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -1142,6 +1143,30 @@ static int cs35l41_dsp_init(struct cs35l41_private *cs35l41)
 	return ret;
 }
 
+static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
+{
+	acpi_handle handle = ACPI_HANDLE(cs35l41->dev);
+	const char *sub;
+
+	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
+	if (!handle)
+		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);
+	}
+
+	cs35l41->dsp.system_name = sub;
+	dev_dbg(cs35l41->dev, "Subsystem ID: %s\n", cs35l41->dsp.system_name);
+
+	return 0;
+}
+
 int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *hw_cfg)
 {
 	u32 regid, reg_revid, i, mtl_revid, int_status, chipid_match;
@@ -1270,6 +1295,10 @@ int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *
 		goto err;
 	}
 
+	ret = cs35l41_acpi_get_name(cs35l41);
+	if (ret < 0)
+		goto err;
+
 	ret = cs35l41_dsp_init(cs35l41);
 	if (ret < 0)
 		goto err;
@@ -1316,6 +1345,7 @@ void cs35l41_remove(struct cs35l41_private *cs35l41)
 	pm_runtime_disable(cs35l41->dev);
 
 	regmap_write(cs35l41->regmap, CS35L41_IRQ1_MASK1, 0xFFFFFFFF);
+	kfree(cs35l41->dsp.system_name);
 	wm_adsp2_remove(&cs35l41->dsp);
 	cs35l41_safe_reset(cs35l41->regmap, cs35l41->hw_cfg.bst_type);