[U-Boot] [PATCH 02/14] arm: Optionally use existing atags in bootm.c

[Pali Rohár]

This patch adapts the bootm command so that it can use an existing atags command
set up by a previous bootloader. If the environment variable "atagaddr" is unset,
bootm behaves as normal. If "atagaddr" is set, bootm will use atags address from
environment variable and also append new boot args (if specified in u-boot). For
example, if a previous boot loader already set up the atags struct at 0x80000100:

setenv atagaddr 0x80000100; bootm 0x80008000

Signed-off-by: Pali Rohár <pali.rohar at gmail.com>
---
Changes since original version:
   - Added info to README file
   - Added local define CONFIG_SETUP_ANY_TAG
   - Fixed compile warning
   - Fixed commit message
   - Check if atagaddr is not NULL

 README               |    2 ++
 arch/arm/lib/bootm.c |   39 ++++++++++++++++++++++++++++++++-------
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/README b/README
index 9d713e8..8c3b98a 100644
--- a/README
+++ b/README
@@ -3584,6 +3584,8 @@ Some configuration options can be set using Environment Variables.
 
 List of environment variables (most likely not complete):
 
+  atagaddr	- bootm will use ATAGs struct from specified address (arm only)
+
   baudrate	- see CONFIG_BAUDRATE
 
   bootdelay	- see CONFIG_BOOTDELAY
diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
index afa0093..8366dd5 100644
--- a/arch/arm/lib/bootm.c
+++ b/arch/arm/lib/bootm.c
@@ -93,6 +93,14 @@ static void announce_and_cleanup(void)
 	cleanup_before_linux();
 }
 
+#if defined(CONFIG_SETUP_MEMORY_TAGS) || \
+defined(CONFIG_CMDLINE_TAG) || \
+defined(CONFIG_INITRD_TAG) || \
+defined(CONFIG_SERIAL_TAG) || \
+defined(CONFIG_REVISION_TAG)
+#define CONFIG_SETUP_ANY_TAG
+#endif
+
 int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 {
 	bd_t	*bd = gd->bd;
@@ -125,12 +133,22 @@ int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 	debug ("## Transferring control to Linux (at address %08lx) ...\n",
 	       (ulong) kernel_entry);
 
-#if defined (CONFIG_SETUP_MEMORY_TAGS) || \
-    defined (CONFIG_CMDLINE_TAG) || \
-    defined (CONFIG_INITRD_TAG) || \
-    defined (CONFIG_SERIAL_TAG) || \
-    defined (CONFIG_REVISION_TAG)
-	setup_start_tag (bd);
+	s = getenv("atagaddr");
+	if (s)
+		bd->bi_boot_params = simple_strtoul(s, NULL, 16);
+
+	if (bd->bi_boot_params) {
+		printf("Using existing atags at %#lx\n", bd->bi_boot_params);
+
+		params = (struct tag *) bd->bi_boot_params;
+		while (params->hdr.size > 0)
+			params = tag_next(params);
+	} else {
+#ifdef CONFIG_SETUP_ANY_TAG
+		setup_start_tag(bd);
+#endif
+	}
+
 #ifdef CONFIG_SERIAL_TAG
 	setup_serial_tag (&params);
 #endif
@@ -147,8 +165,15 @@ int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 	if (images->rd_start && images->rd_end)
 		setup_initrd_tag (bd, images->rd_start, images->rd_end);
 #endif
-	setup_end_tag(bd);
+
+	if (s) {
+		if (params->hdr.size > 0)
+			setup_end_tag(bd);
+	} else {
+#ifdef CONFIG_SETUP_ANY_TAG
+		setup_end_tag(bd);
 #endif
+	}
 
 	announce_and_cleanup();
 
-- 
1.7.5.4