regmap: irq: Allow using zero value for ack_base

In some cases, clear interrupt register may be at address 0.
This patch allows to use such configurations by adding additional
configuration bit to indicate this.

[With doc fix from Levente Kurusa <levex@linux.com> -- broonie]
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/base/regmap/regmap-irq.c

@@ -113,7 +113,7 @@ static void regmap_irq_sync_unlock(struct irq_data *data)
 		 * OR if there is masked interrupt which hasn't been Acked,
 		 * it'll be ignored in irq handler, then may introduce irq storm
 		 */
-		if (d->mask_buf[i] && d->chip->ack_base) {
+		if (d->mask_buf[i] && (d->chip->ack_base || d->chip->use_ack)) {
 			reg = d->chip->ack_base +
 				(i * map->reg_stride * d->irq_reg_stride);
 			ret = regmap_write(map, reg, d->mask_buf[i]);
@@ -271,7 +271,7 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 	for (i = 0; i < data->chip->num_regs; i++) {
 		data->status_buf[i] &= ~data->mask_buf[i];
 
-		if (data->status_buf[i] && chip->ack_base) {
+		if (data->status_buf[i] && (chip->ack_base || chip->use_ack)) {
 			reg = chip->ack_base +
 				(i * map->reg_stride * data->irq_reg_stride);
 			ret = regmap_write(map, reg, data->status_buf[i]);
@@ -448,7 +448,7 @@ int regmap_add_irq_chip(struct regmap *map, int irq, int irq_flags,
 			goto err_alloc;
 		}
 
-		if (d->status_buf[i] && chip->ack_base) {
+		if (d->status_buf[i] && (chip->ack_base || chip->use_ack)) {
 			reg = chip->ack_base +
 				(i * map->reg_stride * d->irq_reg_stride);
 			ret = regmap_write(map, reg,

include/linux/regmap.h

@@ -498,10 +498,12 @@ struct regmap_irq {
  * @status_base: Base status register address.
  * @mask_base:   Base mask register address.
  * @ack_base:    Base ack address. If zero then the chip is clear on read.
+ *               Using zero value is possible with @use_ack bit.
  * @wake_base:   Base address for wake enables.  If zero unsupported.
  * @irq_reg_stride:  Stride to use for chips where registers are not contiguous.
  * @init_ack_masked: Ack all masked interrupts once during initalization.
  * @mask_invert: Inverted mask register: cleared bits are masked out.
+ * @use_ack:     Use @ack register even if it is zero.
  * @wake_invert: Inverted wake register: cleared bits are wake enabled.
  * @runtime_pm:  Hold a runtime PM lock on the device when accessing it.
  *
@@ -520,6 +522,7 @@ struct regmap_irq_chip {
 	unsigned int irq_reg_stride;
 	bool init_ack_masked:1;
 	bool mask_invert:1;
+	bool use_ack:1;
 	bool wake_invert:1;
 	bool runtime_pm:1;