-/* Reserved address space for UAR mapping. */
-#define MLX5_UAR_SIZE (1ULL << 32)
-
-/* Offset of reserved UAR address space to hugepage memory. Offset is used here
- * to minimize possibility of address next to hugepage being used by other code
- * in either primary or secondary process, failing to map TX UAR would make TX
- * packets invisible to HW.
+/* Maximum number of UAR pages used by a port,
+ * These are the size and mask for an array of mutexes used to synchronize
+ * the access to port's UARs on platforms that do not support 64 bit writes.
+ * In such systems it is possible to issue the 64 bits DoorBells through two
+ * consecutive writes, each write 32 bits. The access to a UAR page (which can
+ * be accessible by all threads in the process) must be synchronized
+ * (for example, using a semaphore). Such a synchronization is not required
+ * when ringing DoorBells on different UAR pages.
+ * A port with 512 Tx queues uses 8, 4kBytes, UAR pages which are shared
+ * among the ports.