power: supply: max17042_battery: Fix ACPI interrupt issues

On some x86/ACPI boards the DSDT defines an ACPI event handler for
the max17047 IRQ, this causes several problems:

1) We need to share the IRQ to avoid an error getting it

2) Even of we are willing to share, we may fail to share because some
   DSDTs claim it exclusivly

3) If we are unable to share the IRQ, or the IRQ is only listed as an
   ACPI event source and not in the max1704 firmware node, then the
   charge threshold IRQ (which is used to give an IRQ every 1 percent
   charge change) becomes a problem, the ACPI event handler will not
   update this to the next 1 percent threshold, so the IRQ keeps firing
   and we get an IRQ storm pegging 1 CPU core.

   This happens despite the max17042 driver not setting the charge
   threshold because Windows uses it and leaves it set on reboot.

   So if we are unable to get the IRQ we need to reprogram the
   charge threshold to its disabled setting.

This commit fixes al of the above, while at it it also makes the error
msg when being unable to get the IRQ consistent with other messages.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

drivers/power/supply/max17042_battery.c

@@ -1050,11 +1050,18 @@ static int max17042_probe(struct i2c_client *client,
 	}
 
 	if (client->irq) {
+		unsigned int flags = IRQF_TRIGGER_FALLING | IRQF_ONESHOT;
+
+		/*
+		 * On ACPI systems the IRQ may be handled by ACPI-event code,
+		 * so we need to share (if the ACPI code is willing to share).
+		 */
+		if (acpi_id)
+			flags |= IRQF_SHARED | IRQF_PROBE_SHARED;
+
 		ret = devm_request_threaded_irq(&client->dev, client->irq,
 						NULL,
-						max17042_thread_handler,
-						IRQF_TRIGGER_FALLING |
-						IRQF_ONESHOT,
+						max17042_thread_handler, flags,
 						chip->battery->desc->name,
 						chip);
 		if (!ret) {
@@ -1064,10 +1071,13 @@ static int max17042_probe(struct i2c_client *client,
 			max17042_set_soc_threshold(chip, 1);
 		} else {
 			client->irq = 0;
-			dev_err(&client->dev, "%s(): cannot get IRQ\n",
-				__func__);
+			if (ret != -EBUSY)
+				dev_err(&client->dev, "Failed to get IRQ\n");
 		}
 	}
+	/* Not able to update the charge threshold when exceeded? -> disable */
+	if (!client->irq)
+		regmap_write(chip->regmap, MAX17042_SALRT_Th, 0xff00);
 
 	regmap_read(chip->regmap, MAX17042_STATUS, &val);
 	if (val & STATUS_POR_BIT) {