powerpc/powernv: Fix endian issue in opal_xscom_read

opal_xscom_read uses a pointer to return the data so we need
to byteswap it on LE builds.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/opal.h

@@ -720,7 +720,7 @@ int64_t opal_pci_next_error(uint64_t phb_id, uint64_t *first_frozen_pe,
 int64_t opal_pci_poll(uint64_t phb_id);
 int64_t opal_return_cpu(void);
 
-int64_t opal_xscom_read(uint32_t gcid, uint32_t pcb_addr, uint64_t *val);
+int64_t opal_xscom_read(uint32_t gcid, uint32_t pcb_addr, __be64 *val);
 int64_t opal_xscom_write(uint32_t gcid, uint32_t pcb_addr, uint64_t val);
 
 int64_t opal_lpc_write(uint32_t chip_id, enum OpalLPCAddressType addr_type,

arch/powerpc/platforms/powernv/opal-xscom.c

@@ -96,9 +96,11 @@ static int opal_scom_read(scom_map_t map, u64 reg, u64 *value)
 {
 	struct opal_scom_map *m = map;
 	int64_t rc;
+	__be64 v;
 
 	reg = opal_scom_unmangle(reg);
-	rc = opal_xscom_read(m->chip, m->addr + reg, (uint64_t *)__pa(value));
+	rc = opal_xscom_read(m->chip, m->addr + reg, (__be64 *)__pa(&v));
+	*value = be64_to_cpu(v);
 	return opal_xscom_err_xlate(rc);
 }