regmap-irq: Add no_status support

Some devices lack status registers, yet expect to handle interrupts.
Introduce a no_status flag to indicate such a configuration, where
rather than read a status register to verify, all interrupts received
are assumed to be active.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/r/bd501b4b5ff88da24d467f75e8c71b4e0e6f21e2.1677515341.git.william.gray@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: William Breathitt Gray

drivers/base/regmap/regmap-irq.c

@@ -433,7 +433,10 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 	 * possible in order to reduce the I/O overheads.
 	 */
 
-	if (chip->num_main_regs) {
+	if (chip->no_status) {
+		/* no status register so default to all active */
+		memset32(data->status_buf, GENMASK(31, 0), chip->num_regs);
+	} else if (chip->num_main_regs) {
 		unsigned int max_main_bits;
 		unsigned long size;
 
@@ -949,12 +952,17 @@ int regmap_add_irq_chip_fwnode(struct fwnode_handle *fwnode,
 			continue;
 
 		/* Ack masked but set interrupts */
-		reg = d->get_irq_reg(d, d->chip->status_base, i);
-		ret = regmap_read(map, reg, &d->status_buf[i]);
-		if (ret != 0) {
-			dev_err(map->dev, "Failed to read IRQ status: %d\n",
-				ret);
-			goto err_alloc;
+		if (d->chip->no_status) {
+			/* no status register so default to all active */
+			d->status_buf[i] = GENMASK(31, 0);
+		} else {
+			reg = d->get_irq_reg(d, d->chip->status_base, i);
+			ret = regmap_read(map, reg, &d->status_buf[i]);
+			if (ret != 0) {
+				dev_err(map->dev, "Failed to read IRQ status: %d\n",
+					ret);
+				goto err_alloc;
+			}
 		}
 
 		if (chip->status_invert)

include/linux/regmap.h

@@ -1567,6 +1567,7 @@ struct regmap_irq_chip_data;
  *		      the need for a @sub_reg_offsets table.
  * @status_invert: Inverted status register: cleared bits are active interrupts.
  * @runtime_pm:  Hold a runtime PM lock on the device when accessing it.
+ * @no_status: No status register: all interrupts assumed generated by device.
  *
  * @num_regs:    Number of registers in each control bank.
  * @irqs:        Descriptors for individual IRQs.  Interrupt numbers are
@@ -1631,6 +1632,7 @@ struct regmap_irq_chip {
 	unsigned int clear_on_unmask:1;
 	unsigned int not_fixed_stride:1;
 	unsigned int status_invert:1;
+	unsigned int no_status:1;
 
 	int num_regs;