[PATCH 3/4] ppc: bootm: relocate fdt to valid boot memory

[Renaud Barbier]

For the MPC85xx family of SOCs Linux expects any boot firmware
information to be passed in the first 64MiB of memory. This adds support
to ensure that the device tree is relocated to a valid location if it is
outside that address range.

For the other SOC family currently present in the ppc architecture, the
default is not to relocate as at Linux startup the virtual address
equals the physical address.

Signed-off-by: Renaud Barbier <renaud.barbier at ge.com>
---
 arch/ppc/include/asm/processor.h |  3 +++
 arch/ppc/lib/ppclinux.c          | 49 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/arch/ppc/include/asm/processor.h b/arch/ppc/include/asm/processor.h
index 04cfb60..9145257 100644
--- a/arch/ppc/include/asm/processor.h
+++ b/arch/ppc/include/asm/processor.h
@@ -966,8 +966,11 @@ struct cpu_type {
 struct cpu_type *identify_cpu(u32 ver);
 
 #if defined(CONFIG_MPC85xx)
+#define LINUX_TLB1_MAX_ADDR	((void *)(64 << 20))
 #define CPU_TYPE_ENTRY(n, v, nc) \
 	{ .name = #n, .soc_ver = SVR_##v, .num_cores = (nc), }
+#else
+#define LINUX_TLB1_MAX_ADDR	((void *)0xffffffff)
 #endif
 #ifndef CONFIG_MACH_SPECIFIC
 extern int _machine;
diff --git a/arch/ppc/lib/ppclinux.c b/arch/ppc/lib/ppclinux.c
index ef69ead..7c30ac3 100644
--- a/arch/ppc/lib/ppclinux.c
+++ b/arch/ppc/lib/ppclinux.c
@@ -4,12 +4,45 @@
 #include <command.h>
 #include <image.h>
 #include <init.h>
+#include <malloc.h>
 #include <environment.h>
 #include <asm/bitops.h>
+#include <asm/processor.h>
 #include <boot.h>
 #include <errno.h>
 #include <fs.h>
 
+static int bootm_relocate_fdt(void *addr, struct image_data *data)
+{
+	if (addr < LINUX_TLB1_MAX_ADDR) {
+		/* The kernel is within  the boot TLB mapping.
+		 * Put the DTB above if there is no space
+		 * below.
+		 */
+		if (addr < (void *)data->oftree->totalsize) {
+			addr = (void *)PAGE_ALIGN((phys_addr_t)addr +
+					data->os->header.ih_size);
+			addr += data->oftree->totalsize;
+			if (addr < LINUX_TLB1_MAX_ADDR)
+				addr = LINUX_TLB1_MAX_ADDR;
+		}
+	}
+
+	if (addr > LINUX_TLB1_MAX_ADDR) {
+		pr_crit("Unable to relocate DTB to Linux TLB\n");
+		return 1;
+	}
+
+	addr = (void *)PAGE_ALIGN_DOWN((phys_addr_t)addr -
+			data->oftree->totalsize);
+	memcpy(addr, data->oftree, data->oftree->totalsize);
+	free(data->oftree);
+	data->oftree = addr;
+
+	pr_info("Relocating device tree to 0x%p\n", addr);
+	return 0;
+}
+
 static int do_bootm_linux(struct image_data *data)
 {
 	void	(*kernel)(void *, void *, unsigned long,
@@ -24,6 +57,20 @@ static int do_bootm_linux(struct image_data *data)
 		return -EINVAL;
 	}
 
+	/* Relocate the device tree if outside the initial
+	 * Linux mapped TLB.
+	 */
+	if (IS_ENABLED(CONFIG_MPC85xx)) {
+		void *addr = data->oftree;
+
+		if ((addr + data->oftree->totalsize) > LINUX_TLB1_MAX_ADDR) {
+			addr = (void *)data->os_address;
+
+			if (bootm_relocate_fdt(addr, data))
+				goto error;
+		}
+	}
+
 	fdt_add_reserve_map(data->oftree);
 
 	kernel = (void *)(data->os_address + data->os_entry);
@@ -40,7 +87,7 @@ static int do_bootm_linux(struct image_data *data)
 
 	reset_cpu(0);
 
-	/* not reached */
+error:
 	return -1;
 }
 
-- 
1.8.3.4