regmap: irq: Add support for chips without separate IRQ status

Some GPIO chips allow to rise an IRQ on GPIO level changes but do not
provide an IRQ status for each separate line: only the current gpio
level can be retrieved.

Add support for these chips, emulating IRQ status by comparing GPIO
levels with the levels during the previous interrupt.

Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20250522-mdb-max7360-support-v9-5-74fc03517e41@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: mbriand

drivers/base/regmap/regmap-irq.c

@@ -6,11 +6,13 @@
 //
 // Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
 
+#include <linux/array_size.h>
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
+#include <linux/overflow.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
@@ -33,6 +35,7 @@ struct regmap_irq_chip_data {
 	void *status_reg_buf;
 	unsigned int *main_status_buf;
 	unsigned int *status_buf;
+	unsigned int *prev_status_buf;
 	unsigned int *mask_buf;
 	unsigned int *mask_buf_def;
 	unsigned int *wake_buf;
@@ -332,27 +335,13 @@ static inline int read_sub_irq_data(struct regmap_irq_chip_data *data,
 	return ret;
 }
 
-static irqreturn_t regmap_irq_thread(int irq, void *d)
+static int read_irq_data(struct regmap_irq_chip_data *data)
 {
-	struct regmap_irq_chip_data *data = d;
 	const struct regmap_irq_chip *chip = data->chip;
 	struct regmap *map = data->map;
 	int ret, i;
-	bool handled = false;
 	u32 reg;
 
-	if (chip->handle_pre_irq)
-		chip->handle_pre_irq(chip->irq_drv_data);
-
-	if (chip->runtime_pm) {
-		ret = pm_runtime_get_sync(map->dev);
-		if (ret < 0) {
-			dev_err(map->dev, "IRQ thread failed to resume: %d\n",
-				ret);
-			goto exit;
-		}
-	}
-
 	/*
 	 * Read only registers with active IRQs if the chip has 'main status
 	 * register'. Else read in the statuses, using a single bulk read if
@@ -379,10 +368,8 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 			reg = data->get_irq_reg(data, chip->main_status, i);
 			ret = regmap_read(map, reg, &data->main_status_buf[i]);
 			if (ret) {
-				dev_err(map->dev,
-					"Failed to read IRQ status %d\n",
-					ret);
-				goto exit;
+				dev_err(map->dev, "Failed to read IRQ status %d\n", ret);
+				return ret;
 			}
 		}
 
@@ -398,10 +385,8 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 				ret = read_sub_irq_data(data, b);
 
 				if (ret != 0) {
-					dev_err(map->dev,
-						"Failed to read IRQ status %d\n",
-						ret);
-					goto exit;
+					dev_err(map->dev, "Failed to read IRQ status %d\n", ret);
+					return ret;
 				}
 			}
 
@@ -418,9 +403,8 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 				       data->status_reg_buf,
 				       chip->num_regs);
 		if (ret != 0) {
-			dev_err(map->dev, "Failed to read IRQ status: %d\n",
-				ret);
-			goto exit;
+			dev_err(map->dev, "Failed to read IRQ status: %d\n", ret);
+			return ret;
 		}
 
 		for (i = 0; i < data->chip->num_regs; i++) {
@@ -436,7 +420,7 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 				break;
 			default:
 				BUG();
-				goto exit;
+				return -EIO;
 			}
 		}
 
@@ -447,10 +431,8 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 			ret = regmap_read(map, reg, &data->status_buf[i]);
 
 			if (ret != 0) {
-				dev_err(map->dev,
-					"Failed to read IRQ status: %d\n",
-					ret);
-				goto exit;
+				dev_err(map->dev, "Failed to read IRQ status: %d\n", ret);
+				return ret;
 			}
 		}
 	}
@@ -459,6 +441,42 @@ static irqreturn_t regmap_irq_thread(int irq, void *d)
 		for (i = 0; i < data->chip->num_regs; i++)
 			data->status_buf[i] = ~data->status_buf[i];
 
+	return 0;
+}
+
+static irqreturn_t regmap_irq_thread(int irq, void *d)
+{
+	struct regmap_irq_chip_data *data = d;
+	const struct regmap_irq_chip *chip = data->chip;
+	struct regmap *map = data->map;
+	int ret, i;
+	bool handled = false;
+	u32 reg;
+
+	if (chip->handle_pre_irq)
+		chip->handle_pre_irq(chip->irq_drv_data);
+
+	if (chip->runtime_pm) {
+		ret = pm_runtime_get_sync(map->dev);
+		if (ret < 0) {
+			dev_err(map->dev, "IRQ thread failed to resume: %d\n", ret);
+			goto exit;
+		}
+	}
+
+	ret = read_irq_data(data);
+	if (ret < 0)
+		goto exit;
+
+	if (chip->status_is_level) {
+		for (i = 0; i < data->chip->num_regs; i++) {
+			unsigned int val = data->status_buf[i];
+
+			data->status_buf[i] ^= data->prev_status_buf[i];
+			data->prev_status_buf[i] = val;
+		}
+	}
+
 	/*
 	 * Ignore masked IRQs and ack if we need to; we ack early so
 	 * there is no race between handling and acknowledging the
@@ -705,6 +723,13 @@ int regmap_add_irq_chip_fwnode(struct fwnode_handle *fwnode,
 	if (!d->status_buf)
 		goto err_alloc;
 
+	if (chip->status_is_level) {
+		d->prev_status_buf = kcalloc(chip->num_regs, sizeof(*d->prev_status_buf),
+					     GFP_KERNEL);
+		if (!d->prev_status_buf)
+			goto err_alloc;
+	}
+
 	d->mask_buf = kcalloc(chip->num_regs, sizeof(*d->mask_buf),
 			      GFP_KERNEL);
 	if (!d->mask_buf)
@@ -881,6 +906,16 @@ int regmap_add_irq_chip_fwnode(struct fwnode_handle *fwnode,
 		}
 	}
 
+	/* Store current levels */
+	if (chip->status_is_level) {
+		ret = read_irq_data(d);
+		if (ret < 0)
+			goto err_alloc;
+
+		memcpy(d->prev_status_buf, d->status_buf,
+		       array_size(d->chip->num_regs, sizeof(d->prev_status_buf[0])));
+	}
+
 	ret = regmap_irq_create_domain(fwnode, irq_base, chip, d);
 	if (ret)
 		goto err_alloc;
@@ -908,6 +943,7 @@ int regmap_add_irq_chip_fwnode(struct fwnode_handle *fwnode,
 	kfree(d->mask_buf);
 	kfree(d->main_status_buf);
 	kfree(d->status_buf);
+	kfree(d->prev_status_buf);
 	kfree(d->status_reg_buf);
 	if (d->config_buf) {
 		for (i = 0; i < chip->num_config_bases; i++)
@@ -985,6 +1021,7 @@ void regmap_del_irq_chip(int irq, struct regmap_irq_chip_data *d)
 	kfree(d->main_status_buf);
 	kfree(d->status_reg_buf);
 	kfree(d->status_buf);
+	kfree(d->prev_status_buf);
 	if (d->config_buf) {
 		for (i = 0; i < d->chip->num_config_bases; i++)
 			kfree(d->config_buf[i]);

include/linux/regmap.h

@@ -1641,6 +1641,8 @@ struct regmap_irq_chip_data;
  * @ack_invert:  Inverted ack register: cleared bits for ack.
  * @clear_ack:  Use this to set 1 and 0 or vice-versa to clear interrupts.
  * @status_invert: Inverted status register: cleared bits are active interrupts.
+ * @status_is_level: Status register is actuall signal level: Xor status
+ *		     register with previous value to get active interrupts.
  * @wake_invert: Inverted wake register: cleared bits are wake enabled.
  * @type_in_mask: Use the mask registers for controlling irq type. Use this if
  *		  the hardware provides separate bits for rising/falling edge
@@ -1704,6 +1706,7 @@ struct regmap_irq_chip {
 	unsigned int ack_invert:1;
 	unsigned int clear_ack:1;
 	unsigned int status_invert:1;
+	unsigned int status_is_level:1;
 	unsigned int wake_invert:1;
 	unsigned int type_in_mask:1;
 	unsigned int clear_on_unmask:1;