of: property: Fix fw_devlink handling of interrupt-map

Commit d976c6f4 ("of: property: Add fw_devlink support for
interrupt-map property") tried to do what it says on the tin,
but failed on a couple of points:

- it confuses bytes and cells. Not a huge deal, except when it
  comes to pointer arithmetic

- it doesn't really handle anything but interrupt-maps that have
  their parent #address-cells set to 0

The combinations of the two leads to some serious fun on my M1
box, with plenty of WARN-ON() firing all over the shop, and
amusing values being generated for interrupt specifiers.

Having 2 versions of parsing code for "interrupt-map" was a bad
idea. Now that the common parsing parts have been refactored
into of_irq_parse_imap_parent(), rework the code here to use it
instead and fix the pointer arithmetic.

Note that the dependency will be a bit different than the original code
when the interrupt-map points to another interrupt-map. In this case,
the original code would resolve to the final interrupt controller. Now
the dependency is the parent interrupt-map (which itself should have a
dependency to the parent). It is possible that a node with an
interrupt-map has no driver.

Fixes: d976c6f4 ("of: property: Add fw_devlink support for interrupt-map property")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Co-developed-by: Rob Herring (Arm) <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Anup Patel <apatel@ventanamicro.com>
Link: https://lore.kernel.org/r/20240529-dt-interrupt-map-fix-v2-2-ef86dc5bcd2a@kernel.orgSigned-off-by: Rob Herring (Arm) <robh@kernel.org>

drivers/of/property.c

@@ -1306,10 +1306,10 @@ static struct device_node *parse_interrupts(struct device_node *np,
 static struct device_node *parse_interrupt_map(struct device_node *np,
 					       const char *prop_name, int index)
 {
-	const __be32 *imap, *imap_end, *addr;
+	const __be32 *imap, *imap_end;
 	struct of_phandle_args sup_args;
 	u32 addrcells, intcells;
-	int i, imaplen;
+	int imaplen;
 
 	if (!IS_ENABLED(CONFIG_OF_IRQ))
 		return NULL;
@@ -1322,33 +1322,23 @@ static struct device_node *parse_interrupt_map(struct device_node *np,
 	addrcells = of_bus_n_addr_cells(np);
 
 	imap = of_get_property(np, "interrupt-map", &imaplen);
-	if (!imap || imaplen <= (addrcells + intcells))
+	imaplen /= sizeof(*imap);
+	if (!imap)
 		return NULL;
-	imap_end = imap + imaplen;
 
-	while (imap < imap_end) {
-		addr = imap;
-		imap += addrcells;
+	imap_end = imap + imaplen;
 
-		sup_args.np = np;
-		sup_args.args_count = intcells;
-		for (i = 0; i < intcells; i++)
-			sup_args.args[i] = be32_to_cpu(imap[i]);
-		imap += intcells;
+	for (int i = 0; imap + addrcells + intcells + 1 < imap_end; i++) {
+		imap += addrcells + intcells;
 
-		/*
-		 * Upon success, the function of_irq_parse_raw() returns
-		 * interrupt controller DT node pointer in sup_args.np.
-		 */
-		if (of_irq_parse_raw(addr, &sup_args))
+		imap = of_irq_parse_imap_parent(imap, imap_end - imap, &sup_args);
+		if (!imap)
 			return NULL;
 
-		if (!index)
+		if (i == index)
 			return sup_args.np;
 
 		of_node_put(sup_args.np);
-		imap += sup_args.args_count + 1;
-		index--;
 	}
 
 	return NULL;