i3c: dw: Add support for in-band interrupts

This change adds support for receiving and dequeueing i3c IBIs.

By setting struct dw_i3c_master->ibi_capable before probe, a platform
implementation can select the IBI-enabled version of the i3c_master_ops,
enabling the global IBI infrastrcture for that controller.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/79daeefd7ccb7c935d0c159149df21a6c9a73ffa.1680161823.git.jk@codeconstruct.com.auSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/i3c/master/dw-i3c-master.h

@@ -19,6 +19,7 @@ struct dw_i3c_master_caps {
 
 struct dw_i3c_dat_entry {
 	u8 addr;
+	struct i3c_dev_desc *ibi_dev;
 };
 
 struct dw_i3c_master {
@@ -37,12 +38,22 @@ struct dw_i3c_master {
 	struct clk *core_clk;
 	char version[5];
 	char type[5];
+	bool ibi_capable;
 
 	/*
 	 * Per-device hardware data, used to manage the device address table
 	 * (DAT)
+	 *
+	 * Locking: the devs array may be referenced in IRQ context while
+	 * processing an IBI. However, IBIs (for a specific device, which
+	 * implies a specific DAT entry) can only happen while interrupts are
+	 * requested for that device, which is serialised against other
+	 * insertions/removals from the array by the global i3c infrastructure.
+	 * So, devs_lock protects against concurrent updates to devs->ibi_dev
+	 * between request_ibi/free_ibi and the IBI irq event.
 	 */
 	struct dw_i3c_dat_entry devs[DW_I3C_MAX_DEVS];
+	spinlock_t devs_lock;
 
 	/* platform-specific data */
 	const struct dw_i3c_platform_ops *platform_ops;