soundwire: bus: Allow SoundWire peripherals to register IRQ handlers

Currently the in-band alerts for SoundWire peripherals can only
be communicated to the driver through the interrupt_callback
function. This however is slightly inconvenient for devices that wish
to share IRQ handling code between SoundWire and I2C/SPI, the later
would normally register an IRQ handler with the IRQ subsystem. However
there is no reason the SoundWire in-band IRQs can not also be
communicated as an actual IRQ to the driver.

Add support for SoundWire peripherals to register a normal IRQ
handler to receive SoundWire in-band alerts, allowing code to be
shared across control buses. Note that we allow users to use both the
interrupt_callback and the IRQ handler, this is useful for devices
which must clear additional chip specific SoundWire registers that are
not a part of the normal IRQ flow, or the SoundWire specification.

Signed-off-by: Lucas Tanure <[e-mail]>
Reviewed-by: Pierre-Louis Bossart <[e-mail]>
Acked-by: Bard Liao <[e-mail]>
Acked-by: Vinod Koul <[e-mail]>
Signed-off-by: Charles Keepax <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/soundwire/bus.c

···
 
 #include <linux/acpi.h>
 #include <linux/delay.h>
+#include <linux/irq.h>
 #include <linux/mod_devicetable.h>
 #include <linux/pm_runtime.h>
 #include <linux/soundwire/sdw_registers.h>
···
 	bus->id = rc;
 	return 0;
 }
+
+static int sdw_irq_map(struct irq_domain *h, unsigned int virq,
+		       irq_hw_number_t hw)
+{
+	struct sdw_bus *bus = h->host_data;
+
+	irq_set_chip_data(virq, bus);
+	irq_set_chip(virq, &bus->irq_chip);
+	irq_set_nested_thread(virq, 1);
+	irq_set_noprobe(virq);
+
+	return 0;
+}
+
+static const struct irq_domain_ops sdw_domain_ops = {
+	.map	= sdw_irq_map,
+};
 
 /**
  * sdw_bus_master_add() - add a bus Master instance
···
 	bus->params.curr_bank = SDW_BANK0;
 	bus->params.next_bank = SDW_BANK1;
 
+	bus->irq_chip.name = dev_name(bus->dev);
+	bus->domain = irq_domain_create_linear(fwnode, SDW_MAX_DEVICES,
+					       &sdw_domain_ops, bus);
+	if (!bus->domain) {
+		dev_err(bus->dev, "Failed to add IRQ domain\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(sdw_bus_master_add);
···
 void sdw_bus_master_delete(struct sdw_bus *bus)
 {
 	device_for_each_child(bus->dev, NULL, sdw_delete_slave);
+
+	irq_domain_remove(bus->domain);
+
 	sdw_master_device_del(bus);
 
 	sdw_bus_debugfs_exit(bus);
···
 			if (slave->probed) {
 				struct device *dev = &slave->dev;
 				struct sdw_driver *drv = drv_to_sdw_driver(dev->driver);
+
+				if (slave->prop.use_domain_irq && slave->irq)
+					handle_nested_irq(slave->irq);
 
 				if (drv->ops && drv->ops->interrupt_callback) {
 					slave_intr.sdca_cascade = sdca_cascade;

drivers/soundwire/bus_type.c

···
 	if (drv->ops && drv->ops->read_prop)
 		drv->ops->read_prop(slave);
 
+	if (slave->prop.use_domain_irq) {
+		slave->irq = irq_create_mapping(slave->bus->domain, slave->dev_num);
+		if (!slave->irq)
+			dev_warn(dev, "Failed to map IRQ\n");
+	}
+
 	/* init the sysfs as we have properties now */
 	ret = sdw_slave_sysfs_init(slave);
 	if (ret < 0)
···
 	int ret = 0;
 
 	mutex_lock(&slave->sdw_dev_lock);
+
 	slave->probed = false;
+
+	if (slave->prop.use_domain_irq)
+		irq_dispose_mapping(irq_find_mapping(slave->bus->domain,
+						     slave->dev_num));
+
 	mutex_unlock(&slave->sdw_dev_lock);
 
 	if (drv->remove)

include/linux/soundwire/sdw.h

···
 
 #include <linux/bug.h>
 #include <linux/lockdep_types.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
 #include <linux/mod_devicetable.h>
 #include <linux/bitfield.h>
 
···
  * @clock_reg_supported: the Peripheral implements the clock base and scale
  * registers introduced with the SoundWire 1.2 specification. SDCA devices
  * do not need to set this boolean property as the registers are required.
+ * @use_domain_irq: call actual IRQ handler on slave, as well as callback
  */
 struct sdw_slave_prop {
 	u32 mipi_revision;
···
 	u8 scp_int1_mask;
 	u32 quirks;
 	bool clock_reg_supported;
+	bool use_domain_irq;
 };
 
 #define SDW_SLAVE_QUIRKS_INVALID_INITIAL_PARITY	BIT(0)
···
  * struct sdw_slave - SoundWire Slave
  * @id: MIPI device ID
  * @dev: Linux device
+ * @irq: IRQ number
  * @status: Status reported by the Slave
  * @bus: Bus handle
  * @prop: Slave properties
···
 struct sdw_slave {
 	struct sdw_slave_id id;
 	struct device dev;
+	int irq;
 	enum sdw_slave_status status;
 	struct sdw_bus *bus;
 	struct sdw_slave_prop prop;
···
  * is used to compute and program bus bandwidth, clock, frame shape,
  * transport and port parameters
  * @debugfs: Bus debugfs
+ * @domain: IRQ domain
  * @defer_msg: Defer message
  * @clk_stop_timeout: Clock stop timeout computed
  * @bank_switch_timeout: Bank switch timeout computed
···
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs;
 #endif
+	struct irq_chip irq_chip;
+	struct irq_domain *domain;
 	struct sdw_defer defer_msg;
 	unsigned int clk_stop_timeout;
 	u32 bank_switch_timeout;