s390/boot: add dfltcc= kernel command line parameter

Add the new kernel command line parameter 'dfltcc=' to configure s390
zlib hardware support.

Format: { on | off | def_only | inf_only | always }
 on:       s390 zlib hardware support for compression on
           level 1 and decompression (default)
 off:      No s390 zlib hardware support
 def_only: s390 zlib hardware support for deflate
           only (compression on level 1)
 inf_only: s390 zlib hardware support for inflate
           only (decompression)
 always:   Same as 'on' but ignores the selected compression
           level always using hardware support (used for debugging)

Link: http://lkml.kernel.org/r/20200103223334.20669-5-zaslonko@linux.ibm.com
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Eduard Shishkin <edward6@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/zlib_dfltcc/dfltcc_inflate.c

@@ -3,6 +3,7 @@
 #include "../zlib_inflate/inflate.h"
 #include "dfltcc_util.h"
 #include "dfltcc.h"
+#include <asm/setup.h>
 #include <linux/zutil.h>
 
 /*
@@ -15,6 +16,11 @@ int dfltcc_can_inflate(
     struct inflate_state *state = (struct inflate_state *)strm->state;
     struct dfltcc_state *dfltcc_state = GET_DFLTCC_STATE(state);
 
+    /* Check for kernel dfltcc command line parameter */
+    if (zlib_dfltcc_support == ZLIB_DFLTCC_DISABLED ||
+            zlib_dfltcc_support == ZLIB_DFLTCC_DEFLATE_ONLY)
+        return 0;
+
     /* Unsupported compression settings */
     if (state->wbits != HB_BITS)
         return 0;