Soundwire: stream: program BUSCLOCK_SCALE

We need to program bus clock scale to adjust the bus clock if current
bus clock doesn't fit the bandwidth.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20241218080155.102405-8-yung-chuan.liao@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/bus.c

@@ -813,6 +813,16 @@ void sdw_extract_slave_id(struct sdw_bus *bus,
 }
 EXPORT_SYMBOL(sdw_extract_slave_id);
 
+bool is_clock_scaling_supported_by_slave(struct sdw_slave *slave)
+{
+	/*
+	 * Dynamic scaling is a defined by SDCA. However, some devices expose the class ID but
+	 * can't support dynamic scaling. We might need a quirk to handle such devices.
+	 */
+	return slave->id.class_id;
+}
+EXPORT_SYMBOL(is_clock_scaling_supported_by_slave);
+
 static int sdw_program_device_num(struct sdw_bus *bus, bool *programmed)
 {
 	u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0};

drivers/soundwire/stream.c

@@ -629,8 +629,44 @@ static int sdw_notify_config(struct sdw_master_runtime *m_rt)
 static int sdw_program_params(struct sdw_bus *bus, bool prepare)
 {
 	struct sdw_master_runtime *m_rt;
+	struct sdw_slave *slave;
 	int ret = 0;
+	u32 addr1;
+
+	/* Check if all Peripherals comply with SDCA */
+	list_for_each_entry(slave, &bus->slaves, node) {
+		if (!slave->dev_num_sticky)
+			continue;
+		if (!is_clock_scaling_supported_by_slave(slave)) {
+			dev_dbg(&slave->dev, "The Peripheral doesn't comply with SDCA\n");
+			goto manager_runtime;
+		}
+	}
+
+	if (bus->params.next_bank)
+		addr1 = SDW_SCP_BUSCLOCK_SCALE_B1;
+	else
+		addr1 = SDW_SCP_BUSCLOCK_SCALE_B0;
+
+	/* Program SDW_SCP_BUSCLOCK_SCALE if all Peripherals comply with SDCA */
+	list_for_each_entry(slave, &bus->slaves, node) {
+		int scale_index;
+		u8 base;
+
+		if (!slave->dev_num_sticky)
+			continue;
+		scale_index = sdw_slave_get_scale_index(slave, &base);
+		if (scale_index < 0)
+			return scale_index;
+
+		ret = sdw_write_no_pm(slave, addr1, scale_index);
+		if (ret < 0) {
+			dev_err(&slave->dev, "SDW_SCP_BUSCLOCK_SCALE register write failed\n");
+			return ret;
+		}
+	}
 
+manager_runtime:
 	list_for_each_entry(m_rt, &bus->m_rt_list, bus_node) {
 
 		/*

include/linux/soundwire/sdw.h

@@ -1041,6 +1041,7 @@ int sdw_bus_exit_clk_stop(struct sdw_bus *bus);
 
 int sdw_compare_devid(struct sdw_slave *slave, struct sdw_slave_id id);
 void sdw_extract_slave_id(struct sdw_bus *bus, u64 addr, struct sdw_slave_id *id);
+bool is_clock_scaling_supported_by_slave(struct sdw_slave *slave);
 
 #if IS_ENABLED(CONFIG_SOUNDWIRE)