dcdbas: force SMI to happen when expected

commit dd65c736 upstream.

The dcdbas driver can do an I/O write to cause a SMI to occur.  The SMI handler
looks at certain registers and memory locations, so the SMI needs to happen
immediately.  On some systems I/O writes are posted, though, causing the SMI to
happen well after the "outb" occurred, which causes random failures.  Following
the "outb" with an "inb" forces the write to go through even if it is posted.
Signed-off-by: Stuart Hayes <stuart_hayes@yahoo.com>
Acked-by: Doug Warzecha <douglas_warzecha@dell.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/firmware/dcdbas.c

@@ -267,8 +267,10 @@ int dcdbas_smi_request(struct smi_cmd *smi_cmd)
 	}
 
 	/* generate SMI */
+	/* inb to force posted write through and make SMI happen now */
 	asm volatile (
-		"outb %b0,%w1"
+		"outb %b0,%w1\n"
+		"inb %w1"
 		: /* no output args */
 		: "a" (smi_cmd->command_code),
 		  "d" (smi_cmd->command_address),