mfd: max77620: Fix potential IRQ chip conflict when probing two devices

MAX77620 is most likely always a single device on the board, however
nothing stops board designers to have two of them, thus same device
driver could probe twice. Or user could manually try to probing second
time.

Device driver is not ready for that case, because it allocates
statically 'struct regmap_irq_chip' as non-const and stores during
probe in 'irq_drv_data' member a pointer to per-probe state
container ('struct max77620_chip'). devm_regmap_add_irq_chip() does not
make a copy of 'struct regmap_irq_chip' but store the pointer.

Second probe - either successful or failure - would overwrite the
'irq_drv_data' from previous device probe, so interrupts would be
executed in a wrong context.

Cc: [e-mail]
Fixes: 3df140d11c6d ("mfd: max77620: Mask/unmask interrupt before/after servicing it")
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/max77620.c

···
 	return ret;
 }
 
-static struct regmap_irq_chip max77620_top_irq_chip = {
+static const struct regmap_irq_chip max77620_top_irq_chip = {
 	.name = "max77620-top",
 	.irqs = max77620_top_irqs,
 	.num_irqs = ARRAY_SIZE(max77620_top_irqs),
···
 	const struct i2c_device_id *id = i2c_client_get_device_id(client);
 	const struct regmap_config *rmap_config;
 	struct max77620_chip *chip;
+	struct regmap_irq_chip *chip_desc;
 	const struct mfd_cell *mfd_cells;
 	int n_mfd_cells;
 	bool pm_off;
···
 		return -ENOMEM;
 
 	i2c_set_clientdata(client, chip);
+
+	chip_desc = devm_kmemdup(&client->dev, &max77620_top_irq_chip,
+				 sizeof(max77620_top_irq_chip),
+				 GFP_KERNEL);
+	if (!chip_desc)
+		return -ENOMEM;
+	chip_desc->irq_drv_data = chip;
+
 	chip->dev = &client->dev;
 	chip->chip_irq = client->irq;
 	chip->chip_id = (enum max77620_chip_id)id->driver_data;
···
 	if (ret < 0)
 		return ret;
 
-	max77620_top_irq_chip.irq_drv_data = chip;
 	ret = devm_regmap_add_irq_chip(chip->dev, chip->rmap, client->irq,
 				       IRQF_ONESHOT | IRQF_SHARED, 0,
-				       &max77620_top_irq_chip,
-				       &chip->top_irq_data);
+				       chip_desc, &chip->top_irq_data);
 	if (ret < 0) {
 		dev_err(chip->dev, "Failed to add regmap irq: %d\n", ret);
 		return ret;