powerpc/papr_scm: Properly handle UUID types and API

Parse to and export from UUID own type, before dereferencing.
This also fixes wrong comment (Little Endian UUID is something else)
and should eliminate the direct strict types assignments.

Fixes: 43001c52b6 ("powerpc/papr_scm: Use ibm,unit-guid as the iset cookie")
Fixes: 259a948c4b ("powerpc/pseries/scm: Use a specific endian format for storing uuid from the device tree")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210616134303.58185-1-andriy.shevchenko@linux.intel.com

arch/powerpc/platforms/pseries/papr_scm.c

@@ -18,6 +18,7 @@
 #include <asm/plpar_wrappers.h>
 #include <asm/papr_pdsm.h>
 #include <asm/mce.h>
+#include <asm/unaligned.h>
 
 #define BIND_ANY_ADDR (~0ul)
 
@@ -1101,8 +1102,9 @@ static int papr_scm_probe(struct platform_device *pdev)
 	u32 drc_index, metadata_size;
 	u64 blocks, block_size;
 	struct papr_scm_priv *p;
+	u8 uuid_raw[UUID_SIZE];
 	const char *uuid_str;
-	u64 uuid[2];
+	uuid_t uuid;
 	int rc;
 
 	/* check we have all the required DT properties */
@@ -1145,16 +1147,23 @@ static int papr_scm_probe(struct platform_device *pdev)
 	p->hcall_flush_required = of_property_read_bool(dn, "ibm,hcall-flush-required");
 
 	/* We just need to ensure that set cookies are unique across */
-	uuid_parse(uuid_str, (uuid_t *) uuid);
+	uuid_parse(uuid_str, &uuid);
+
 	/*
-	 * cookie1 and cookie2 are not really little endian
-	 * we store a little endian representation of the
-	 * uuid str so that we can compare this with the label
-	 * area cookie irrespective of the endian config with which
-	 * the kernel is built.
+	 * The cookie1 and cookie2 are not really little endian.
+	 * We store a raw buffer representation of the
+	 * uuid string so that we can compare this with the label
+	 * area cookie irrespective of the endian configuration
+	 * with which the kernel is built.
+	 *
+	 * Historically we stored the cookie in the below format.
+	 * for a uuid string 72511b67-0b3b-42fd-8d1d-5be3cae8bcaa
+	 *	cookie1 was 0xfd423b0b671b5172
+	 *	cookie2 was 0xaabce8cae35b1d8d
 	 */
-	p->nd_set.cookie1 = cpu_to_le64(uuid[0]);
-	p->nd_set.cookie2 = cpu_to_le64(uuid[1]);
+	export_uuid(uuid_raw, &uuid);
+	p->nd_set.cookie1 = get_unaligned_le64(&uuid_raw[0]);
+	p->nd_set.cookie2 = get_unaligned_le64(&uuid_raw[8]);
 
 	/* might be zero */
 	p->metadata_size = metadata_size;