[PATCH v2] spl: fit: List DTOs applied by SPL in U-Boot control DT

[Marek Vasut]

Insert /u-boot,spl-applied-dto-<dto-name> = <index> property into the
U-Boot control DT during SPL DTO application process. This can be used
by user to inspect which DTOs got applied by the SPL and in which order
from running U-Boot.

Example:
```
u-boot=> fdt addr $fdtcontroladdr && fdt list /
Working FDT set to aee9aeb0
/ {
        u-boot,spl-applied-dto-fdt-dto-imx8mp-dhcom-pdk3-overlay-rev100 = <0x00000005>;
        u-boot,spl-applied-dto-fdt-dto-imx8mp-dhcom-som-overlay-rev100 = <0x00000004>;
        u-boot,spl-applied-dto-fdt-dto-imx8mp-dhcom-pdk-overlay-eth2xfast = <0x00000003>;
        u-boot,spl-applied-dto-fdt-dto-imx8mp-dhcom-som-overlay-eth2xfast = <0x00000002>;
...
```

Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: Manoj Sai <abbaraju.manojsai at amarulasolutions.com>
Cc: Sean Anderson <seanga2 at gmail.com>
Cc: Simon Glass <sjg at chromium.org>
Cc: Suniel Mahesh <sunil at amarulasolutions.com>
Cc: Tom Rini <trini at konsulko.com>
Cc: u-boot at dh-electronics.com
Cc: u-boot at lists.denx.de
---
V2: - Expand the DT by one more byte to cater for trailing NUL byte
    - Update comment related to the expansion of DT
    - Flip the !ret conditional, which was incorrect and missed
    - Expand prefix to u-boot,spl-applied-dto-
    - Document the binding
---
 common/spl/spl_fit.c                | 29 +++++++++++++++++++++++++++--
 doc/device-tree-bindings/config.txt | 11 +++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/common/spl/spl_fit.c b/common/spl/spl_fit.c
index 988125be008..0a6b5ea8212 100644
--- a/common/spl/spl_fit.c
+++ b/common/spl/spl_fit.c
@@ -363,6 +363,7 @@ static int spl_fit_append_fdt(struct spl_image_info *spl_image,
 {
 	struct spl_image_info image_info;
 	int node, ret = 0, index = 0;
+	char dtoname[256];
 
 	/*
 	 * Use the address following the image as target address for the
@@ -448,9 +449,13 @@ static int spl_fit_append_fdt(struct spl_image_info *spl_image,
 			if (ret < 0)
 				break;
 
-			/* Make room in FDT for changes from the overlay */
+			/*
+			 * Make room in FDT for changes from the overlay,
+			 * the overlay name and the trailing NUL byte in
+			 * that name.
+			 */
 			ret = fdt_increase_size(spl_image->fdt_addr,
-						image_info.size);
+						image_info.size + strlen(str) + 1);
 			if (ret < 0)
 				break;
 
@@ -464,6 +469,26 @@ static int spl_fit_append_fdt(struct spl_image_info *spl_image,
 
 			debug("%s: DT overlay %s applied\n", __func__,
 			      fit_get_name(ctx->fit, node, NULL));
+
+			/*
+			 * Insert /u-boot,<dto-name> = <index> property into
+			 * the U-Boot control DT. This can be used by user
+			 * to inspect which DTOs got applied by the SPL from
+			 * a running U-Boot.
+			 */
+			snprintf(dtoname, sizeof(dtoname), "u-boot,spl-applied-dto-%s", str);
+			ret = fdt_setprop_u32(spl_image->fdt_addr, 0, dtoname,
+					      index);
+			if (ret) {
+				/*
+				 * The DTO itself was applied, do not treat the
+				 * insertion of /u-boot,<dto-name> as an error
+				 * so the system can possibly boot somehow.
+				 */
+				debug("%s: DT overlay %s name not inserted into / node (%d)\n",
+				      __func__,
+				      fit_get_name(ctx->fit, node, NULL), ret);
+			}
 		}
 		free(tmpbuffer);
 		if (ret)
diff --git a/doc/device-tree-bindings/config.txt b/doc/device-tree-bindings/config.txt
index f50c68bbdc3..7aa6d9a72c6 100644
--- a/doc/device-tree-bindings/config.txt
+++ b/doc/device-tree-bindings/config.txt
@@ -95,6 +95,17 @@ rootdisk-offset (int)
 silent-console (int)
 	If present and non-zero, the console is silenced by default on boot.
 
+u-boot,spl-applied-dto-* (int)
+	Emitted by SPL into U-Boot control DT root node in case a DTO from
+	fitImage was applied on top of U-Boot control DT by the SPL fitImage
+	loader. The single integer cell indicates in which order was the DTO
+	applied by the SPL and matches the index of the DTO in the fitImage.
+	DTOs in fitImage may be skipped using board_spl_fit_append_fdt_skip(),
+	therefore the integers might not be monotonically incrementing, there
+	may be gaps. This property can be used to determine which DTOs were
+	applied by the SPL from running U-Boot by inspecting the U-Boot
+	control DT.
+
 u-boot,spl-payload-offset (int)
 	If present (and SPL is controlled by the device-tree), this allows
 	to override the CONFIG_SYS_SPI_U_BOOT_OFFS setting using a value
-- 
2.43.0