ASoC: cs35l56: Support clock stop mode 1 if enabled in ACPI

Report the ability to support SoundWire clock-stop mode 1 if this is
enabled in ACPI. Mode 1 allows the device to lose state, so it can
reduce power consumption in clock-stop. Also add the necessary
handling to wait for re-enumeration on resume.

This does not use sdw_slave_read_prop(), because that also fills in
other properties from ACPI that were not previously set by the driver
and this has been observed to break some systems. Instead, the
"mipi-sdw-clock-stop-mode1-supported" property is checked directly.

When a SoundWire peripheral has been put into clock-stop mode 1 it
must be re-enumerated after the clock is restarted. A new flag
sdw_in_clock_stop_1 is set to true in cs35l56_sdw_clk_stop() if the
SoundWire core notifies that it is entering clock-stop 1.
cs35l56_sdw_handle_unattach() will wait for re-enumeration if
sdw_in_clock_stop_1 is true.

sdw_in_clock_stop_1 will be reset to false when an ATTACH notification
is received in cs35l56_sdw_update_status().

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20260311142153.2201761-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: rfvirgil

sound/soc/codecs/cs35l56-sdw.c

@@ -14,6 +14,7 @@
 #include <linux/soundwire/sdw.h>
 #include <linux/soundwire/sdw_registers.h>
 #include <linux/soundwire/sdw_type.h>
+#include <linux/string_choices.h>
 #include <linux/swab.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
@@ -340,6 +341,14 @@ static int cs35l56_sdw_read_prop(struct sdw_slave *peripheral)
 	struct cs35l56_private *cs35l56 = dev_get_drvdata(&peripheral->dev);
 	struct sdw_slave_prop *prop = &peripheral->prop;
 	struct sdw_dpn_prop *ports;
+	u8 clock_stop_1 = false;
+	int ret;
+
+	ret = fwnode_property_read_u8(dev_fwnode(cs35l56->base.dev),
+				      "mipi-sdw-clock-stop-mode1-supported",
+				      &clock_stop_1);
+	if (ret == 0)
+		prop->clk_stop_mode1 = !!clock_stop_1;
 
 	ports = devm_kcalloc(cs35l56->base.dev, 2, sizeof(*ports), GFP_KERNEL);
 	if (!ports)
@@ -363,6 +372,9 @@ static int cs35l56_sdw_read_prop(struct sdw_slave *peripheral)
 	ports[1].ch_prep_timeout = 10;
 	prop->src_dpn_prop = &ports[1];
 
+	dev_dbg(&peripheral->dev, "clock stop mode 1 supported: %s\n",
+		str_yes_no(prop->clk_stop_mode1));
+
 	return 0;
 }
 
@@ -374,6 +386,7 @@ static int cs35l56_sdw_update_status(struct sdw_slave *peripheral,
 	switch (status) {
 	case SDW_SLAVE_ATTACHED:
 		dev_dbg(cs35l56->base.dev, "%s: ATTACHED\n", __func__);
+		cs35l56->sdw_in_clock_stop_1 = false;
 		if (cs35l56->sdw_attached)
 			break;
 
@@ -399,25 +412,35 @@ static int __maybe_unused cs35l56_sdw_clk_stop(struct sdw_slave *peripheral,
 {
 	struct cs35l56_private *cs35l56 = dev_get_drvdata(&peripheral->dev);
 
-	dev_dbg(cs35l56->base.dev, "%s: mode:%d type:%d\n", __func__, mode, type);
+	dev_dbg(cs35l56->base.dev, "%s: clock_stop_mode%d stage:%d\n", __func__, mode, type);
 
-	return 0;
+	switch (type) {
+	case SDW_CLK_POST_PREPARE:
+		if (mode == SDW_CLK_STOP_MODE1)
+			cs35l56->sdw_in_clock_stop_1 = true;
+		else
+			cs35l56->sdw_in_clock_stop_1 = false;
+		return 0;
+	default:
+		return 0;
+	}
 }
 
 static const struct sdw_slave_ops cs35l56_sdw_ops = {
 	.read_prop = cs35l56_sdw_read_prop,
 	.interrupt_callback = cs35l56_sdw_interrupt,
 	.update_status = cs35l56_sdw_update_status,
-#ifdef DEBUG
 	.clk_stop = cs35l56_sdw_clk_stop,
-#endif
 };
 
 static int __maybe_unused cs35l56_sdw_handle_unattach(struct cs35l56_private *cs35l56)
 {
 	struct sdw_slave *peripheral = cs35l56->sdw_peripheral;
 
-	if (peripheral->unattach_request) {
+	dev_dbg(cs35l56->base.dev, "attached:%u unattach_request:%u in_clock_stop_1:%u\n",
+		cs35l56->sdw_attached, peripheral->unattach_request, cs35l56->sdw_in_clock_stop_1);
+
+	if (cs35l56->sdw_in_clock_stop_1 || peripheral->unattach_request) {
 		/* Cannot access registers until bus is re-initialized. */
 		dev_dbg(cs35l56->base.dev, "Wait for initialization_complete\n");
 		if (!wait_for_completion_timeout(&peripheral->initialization_complete,
@@ -427,6 +450,7 @@ static int __maybe_unused cs35l56_sdw_handle_unattach(struct cs35l56_private *cs
 		}
 
 		peripheral->unattach_request = 0;
+		cs35l56->sdw_in_clock_stop_1 = false;
 
 		/*
 		 * Don't call regcache_mark_dirty(), we can't be sure that the

sound/soc/codecs/cs35l56.h

@@ -42,6 +42,7 @@ struct cs35l56_private {
 	bool sdw_irq_no_unmask;
 	bool soft_resetting;
 	bool sdw_attached;
+	bool sdw_in_clock_stop_1;
 	struct completion init_completion;
 
 	int speaker_id;