[U-Boot] [PATCH v2 01/11] arm: Optionally use existing atags in bootm.c

["Pali Rohár" <pali.rohar@gmail.com>]

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 Roh?r <pali.rohar@gmail.com>
---
Changes since v1:
   - Rebased on u-boot master

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 |   60 ++++++++++++++++++++++++++++++++------------------
 2 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/README b/README
index 43074cf..60ad9c2 100644
--- a/README
+++ b/README
@@ -3687,6 +3687,8 @@ 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 599547d..0f3c97b 100644
--- a/arch/arm/lib/bootm.c
+++ b/arch/arm/lib/bootm.c
@@ -42,6 +42,10 @@ DECLARE_GLOBAL_DATA_PTR;
 	defined(CONFIG_INITRD_TAG) || \
 	defined(CONFIG_SERIAL_TAG) || \
 	defined(CONFIG_REVISION_TAG)
+		#define CONFIG_SETUP_ANY_TAG
+#endif
+
+#ifdef CONFIG_SETUP_ANY_TAG
 static struct tag *params;
 #endif
 
@@ -106,11 +110,7 @@ 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)
+#ifdef CONFIG_SETUP_ANY_TAG
 static void setup_start_tag (bd_t *bd)
 {
 	params = (struct tag *)bd->bi_boot_params;
@@ -217,11 +217,7 @@ void setup_revision_tag(struct tag **in_params)
 }
 #endif
 
-#if defined(CONFIG_SETUP_MEMORY_TAGS) || \
-	defined(CONFIG_CMDLINE_TAG) || \
-	defined(CONFIG_INITRD_TAG) || \
-	defined(CONFIG_SERIAL_TAG) || \
-	defined(CONFIG_REVISION_TAG)
+#ifdef CONFIG_SETUP_ANY_TAG
 static void setup_end_tag(bd_t *bd)
 {
 	params->hdr.tag = ATAG_NONE;
@@ -280,13 +276,23 @@ static void boot_prep_linux(bootm_headers_t *images)
 	} else
 #endif
 	{
-#if defined(CONFIG_SETUP_MEMORY_TAGS) || \
-	defined(CONFIG_CMDLINE_TAG) || \
-	defined(CONFIG_INITRD_TAG) || \
-	defined(CONFIG_SERIAL_TAG) || \
-	defined(CONFIG_REVISION_TAG)
+		char *atagaddr = getenv("atagaddr");
 		debug("using: ATAGS\n");
-		setup_start_tag(gd->bd);
+
+		if (atagaddr)
+			gd->bd->bi_boot_params = simple_strtoul(atagaddr, NULL, 16);
+
+		if (gd->bd->bi_boot_params) {
+			printf("Using existing atags at %#lx\n", gd->bd->bi_boot_params);
+
+			params = (struct tag *) gd->bd->bi_boot_params;
+			while (params->hdr.size > 0)
+				params = tag_next(params);
+		} else {
+#ifdef CONFIG_SETUP_ANY_TAG
+			setup_start_tag(gd->bd);
+#endif
+		}
 #ifdef CONFIG_SERIAL_TAG
 		setup_serial_tag(&params);
 #endif
@@ -297,18 +303,28 @@ static void boot_prep_linux(bootm_headers_t *images)
 		setup_revision_tag(&params);
 #endif
 #ifdef CONFIG_SETUP_MEMORY_TAGS
-		setup_memory_tags(gd->bd);
+		if (!atagaddr)
+			setup_memory_tags(gd->bd);
 #endif
 #ifdef CONFIG_INITRD_TAG
 		if (images->rd_start && images->rd_end)
 			setup_initrd_tag(gd->bd, images->rd_start,
 			images->rd_end);
 #endif
-		setup_end_tag(gd->bd);
-#else /* all tags */
-		printf("FDT and ATAGS support not compiled in - hanging\n");
-		hang();
-#endif /* all tags */
+		if (atagaddr) {
+			if (params->hdr.size > 0)
+				setup_end_tag(gd->bd);
+		} else {
+#ifdef CONFIG_SETUP_ANY_TAG
+			setup_end_tag(gd->bd);
+#endif
+		}
+#ifndef CONFIG_SETUP_ANY_TAG
+		if (!atagaddr) {
+			printf("FDT and ATAGS support not compiled in - hanging\n");
+			hang();
+		}
+#endif
 	}
 }
 
-- 
1.7.9.5