mips: Add reserve-nomap memory type support

It might be necessary to prevent the virtual mapping creation for a
requested memory region. For instance there is a "no-map" property
indicating exactly this feature. In this case we need to not only
reserve the specified region by pretending it doesn't exist in the
memory space, but completely remove the range from system just by
removing it from memblock. The same way it's done in default
early_init_dt_reserve_memory_arch() method.
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Matt Redfearn <matt.redfearn@mips.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

arch/mips/include/asm/bootinfo.h

@@ -92,6 +92,7 @@ extern unsigned long mips_machtype;
 #define BOOT_MEM_ROM_DATA	2
 #define BOOT_MEM_RESERVED	3
 #define BOOT_MEM_INIT_RAM	4
+#define BOOT_MEM_NOMAP		5
 
 /*
  * A memory map that's built upon what was determined

arch/mips/kernel/prom.c

@@ -47,7 +47,9 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
 					phys_addr_t size, bool nomap)
 {
-	add_memory_region(base, size, BOOT_MEM_RESERVED);
+	add_memory_region(base, size,
+			  nomap ? BOOT_MEM_NOMAP : BOOT_MEM_RESERVED);
+
 	return 0;
 }
 

arch/mips/kernel/setup.c

@@ -178,6 +178,7 @@ static bool __init __maybe_unused memory_region_available(phys_addr_t start,
 				in_ram = true;
 			break;
 		case BOOT_MEM_RESERVED:
+		case BOOT_MEM_NOMAP:
 			if ((start >= start_ && start < end_) ||
 			    (start < start_ && start + size >= start_))
 				free = false;
@@ -213,6 +214,9 @@ static void __init print_memory_map(void)
 		case BOOT_MEM_RESERVED:
 			printk(KERN_CONT "(reserved)\n");
 			break;
+		case BOOT_MEM_NOMAP:
+			printk(KERN_CONT "(nomap)\n");
+			break;
 		default:
 			printk(KERN_CONT "type %lu\n", boot_mem_map.map[i].type);
 			break;
@@ -487,6 +491,9 @@ static void __init bootmem_init(void)
 		switch (boot_mem_map.map[i].type) {
 		case BOOT_MEM_RAM:
 			break;
+		case BOOT_MEM_NOMAP: /* Discard the range from the system. */
+			memblock_remove(PFN_PHYS(start), PFN_PHYS(end - start));
+			continue;
 		default: /* Reserve the rest of the memory types at boot time */
 			memblock_reserve(PFN_PHYS(start), PFN_PHYS(end - start));
 			break;
@@ -861,6 +868,7 @@ static void __init resource_init(void)
 			res->flags |= IORESOURCE_SYSRAM;
 			break;
 		case BOOT_MEM_RESERVED:
+		case BOOT_MEM_NOMAP:
 		default:
 			res->name = "reserved";
 		}