image: android: allow booting lz4-compressed kernels

According to Android image format [1], kernel image resides at 1 page
offset from the boot image address. Grab the magic number from there
and allow U-Boot to handle LZ4-compressed KNL binaries instead of
hardcoding compression type to IH_COMP_NONE. Other compression types,
if needed, can be added later.

Tested on H3ULCB-KF using the image detailed in [2].

[1] Excerpt from include/android_image.h
    +-----------------+
    | boot header     | 1 page
    +-----------------+
    | kernel          | n pages
    +-----------------+
    | ramdisk         | m pages
    +-----------------+
    | second stage    | o pages
    +-----------------+

[2] => iminfo 4c000000
    ## Checking Image at 4c000000 ...
    Android image found
    kernel size:      85b9d1
    kernel address:   48080000
    ramdisk size:     54ddbc
    ramdisk addrress: 4a180000
    second size:      0
    second address:   48000800
    tags address:     48000100
    page size:        800
    os_version:       1200012a (ver: 0.9.0, level: 2018.10)
    name:
    cmdline:          buildvariant=userdebug

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>

common/bootm.c

@@ -154,7 +154,7 @@ static int bootm_find_os(cmd_tbl_t *cmdtp, int flag, int argc,
 #ifdef CONFIG_ANDROID_BOOT_IMAGE
 	case IMAGE_FORMAT_ANDROID:
 		images.os.type = IH_TYPE_KERNEL;
-		images.os.comp = IH_COMP_NONE;
+		images.os.comp = android_image_get_kcomp(os_hdr);
 		images.os.os = IH_OS_LINUX;
 
 		images.os.end = android_image_get_end(os_hdr);

common/image-android.c

@@ -8,6 +8,7 @@
 #include <android_image.h>
 #include <malloc.h>
 #include <errno.h>
+#include <asm/unaligned.h>
 
 #define ANDROID_IMAGE_DEFAULT_KERNEL_ADDR	0x10008000
 
@@ -126,6 +127,16 @@ ulong android_image_get_kload(const struct andr_img_hdr *hdr)
 	return android_image_get_kernel_addr(hdr);
 }
 
+ulong android_image_get_kcomp(const struct andr_img_hdr *hdr)
+{
+	const void *p = (void *)((uintptr_t)hdr + hdr->page_size);
+
+	if (get_unaligned_le32(p) == LZ4F_MAGIC)
+		return IH_COMP_LZ4;
+	else
+		return IH_COMP_NONE;
+}
+
 int android_image_get_ramdisk(const struct andr_img_hdr *hdr,
 			      ulong *rd_data, ulong *rd_len)
 {

include/image.h

@@ -306,6 +306,7 @@ enum {
 	IH_COMP_COUNT,
 };
 
+#define LZ4F_MAGIC	0x184D2204	/* LZ4 Magic Number		*/
 #define IH_MAGIC	0x27051956	/* Image Magic Number		*/
 #define IH_NMLEN		32	/* Image Name Length		*/
 
@@ -1312,6 +1313,7 @@ int android_image_get_second(const struct andr_img_hdr *hdr,
 			      ulong *second_data, ulong *second_len);
 ulong android_image_get_end(const struct andr_img_hdr *hdr);
 ulong android_image_get_kload(const struct andr_img_hdr *hdr);
+ulong android_image_get_kcomp(const struct andr_img_hdr *hdr);
 void android_print_contents(const struct andr_img_hdr *hdr);
 
 #endif /* CONFIG_ANDROID_BOOT_IMAGE */

lib/lz4_wrapper.c

@@ -5,6 +5,7 @@
 
 #include <common.h>
 #include <compiler.h>
+#include <image.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
 
@@ -23,8 +24,6 @@ typedef uint64_t U64;
 /* Unaltered (except removing unrelated code) from github.com/Cyan4973/lz4. */
 #include "lz4.c"	/* #include for inlining, do not link! */
 
-#define LZ4F_MAGIC 0x184D2204
-
 struct lz4_frame_header {
 	u32 magic;
 	union {