s390: add cma support

In order to make the cma infrastructure usable we need to add a small
architecture backend which calls dma_contiguous_reserve.
Otherwise we would end up with the cma allocator enabled, but no pool
where memory can be allocated from.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -136,6 +136,7 @@ config S390
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_API_DEBUG
+	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS

arch/s390/include/asm/Kbuild

@@ -1,6 +1,5 @@
-
-
 generic-y += clkdev.h
+generic-y += dma-contiguous.h
 generic-y += export.h
 generic-y += irq_work.h
 generic-y += mcs_spinlock.h

arch/s390/kernel/setup.c

@@ -35,6 +35,7 @@
 #include <linux/root_dev.h>
 #include <linux/console.h>
 #include <linux/kernel_stat.h>
+#include <linux/dma-contiguous.h>
 #include <linux/device.h>
 #include <linux/notifier.h>
 #include <linux/pfn.h>
@@ -903,6 +904,7 @@ void __init setup_arch(char **cmdline_p)
 
 	setup_memory_end();
 	setup_memory();
+	dma_contiguous_reserve(memory_end);
 
 	check_initrd();
 	reserve_crashkernel();