cmd: pxe: add support for FDT overlays

This adds support for specifying FDT overlays in an extlinux/pxelinux
configuration file.

Without this, there is no simple way to apply overlays when the kernel
and fdt is loaded by the pxe command.

This change adds the 'fdtoverlays' keyword for a label, supporting multiple
overlay files to be applied on top of the fdt specified in the 'fdt' or
'devicetree' keyword.

Example:
  label linux
    kernel /Image
    fdt /soc-board.dtb
    fdtoverlays /soc-board-function.dtbo
    append console=ttyS0,115200 root=/dev/mmcblk0p2 rootwait

This code makes usage of a new variable called fdtoverlay_addr_r used to load
the overlay files without overwritting anything important.

Cc: Tom Rini <trini@konsulko.com>
Cc: Andre Heider <a.heider@gmail.com>
Cc: Jernej Škrabec <jernej.skrabec@siol.net>
Cc: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Jernej Škrabec <jernej.skrabec@siol.net>
Reviewed-by: Jernej Škrabec <jernej.skrabec@siol.net>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

3 files changed, 113 insertions, 0 deletions

diff --git a/cmd/pxe_utils.c b/cmd/pxe_utils.c
index b9d9a5786c2..3526a651d79 100644
--- a/cmd/pxe_utils.c
+++ b/cmd/pxe_utils.c
@@ -13,6 +13,8 @@
 #include <mapmem.h>
 #include <lcd.h>
 #include <net.h>
+#include <fdt_support.h>
+#include <linux/libfdt.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <errno.h>
@@ -284,6 +286,9 @@ static void label_destroy(struct pxe_label *label)
 	if (label->fdtdir)
 		free(label->fdtdir);
 
+	if (label->fdtoverlays)
+		free(label->fdtoverlays);
+
 	free(label);
 }
 
@@ -333,6 +338,92 @@ static int label_localboot(struct pxe_label *label)
 }
 
 /*
+ * Loads fdt overlays specified in 'fdtoverlays'.
+ */
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+static void label_boot_fdtoverlay(struct cmd_tbl *cmdtp, struct pxe_label *label)
+{
+	char *fdtoverlay = label->fdtoverlays;
+	struct fdt_header *working_fdt;
+	char *fdtoverlay_addr_env;
+	ulong fdtoverlay_addr;
+	ulong fdt_addr;
+	int err;
+
+	/* Get the main fdt and map it */
+	fdt_addr = simple_strtoul(env_get("fdt_addr_r"), NULL, 16);
+	working_fdt = map_sysmem(fdt_addr, 0);
+	err = fdt_check_header(working_fdt);
+	if (err)
+		return;
+
+	/* Get the specific overlay loading address */
+	fdtoverlay_addr_env = env_get("fdtoverlay_addr_r");
+	if (!fdtoverlay_addr_env) {
+		printf("Invalid fdtoverlay_addr_r for loading overlays\n");
+		return;
+	}
+
+	fdtoverlay_addr = simple_strtoul(fdtoverlay_addr_env, NULL, 16);
+
+	/* Cycle over the overlay files and apply them in order */
+	do {
+		struct fdt_header *blob;
+		char *overlayfile;
+		char *end;
+		int len;
+
+		/* Drop leading spaces */
+		while (*fdtoverlay == ' ')
+			++fdtoverlay;
+
+		/* Copy a single filename if multiple provided */
+		end = strstr(fdtoverlay, " ");
+		if (end) {
+			len = (int)(end - fdtoverlay);
+			overlayfile = malloc(len + 1);
+			strncpy(overlayfile, fdtoverlay, len);
+			overlayfile[len] = '\0';
+		} else
+			overlayfile = fdtoverlay;
+
+		if (!strlen(overlayfile))
+			goto skip_overlay;
+
+		/* Load overlay file */
+		err = get_relfile_envaddr(cmdtp, overlayfile,
+					  "fdtoverlay_addr_r");
+		if (err < 0) {
+			printf("Failed loading overlay %s\n", overlayfile);
+			goto skip_overlay;
+		}
+
+		/* Resize main fdt */
+		fdt_shrink_to_minimum(working_fdt, 8192);
+
+		blob = map_sysmem(fdtoverlay_addr, 0);
+		err = fdt_check_header(blob);
+		if (err) {
+			printf("Invalid overlay %s, skipping\n",
+			       overlayfile);
+			goto skip_overlay;
+		}
+
+		err = fdt_overlay_apply_verbose(working_fdt, blob);
+		if (err) {
+			printf("Failed to apply overlay %s, skipping\n",
+			       overlayfile);
+			goto skip_overlay;
+		}
+
+skip_overlay:
+		if (end)
+			free(overlayfile);
+	} while ((fdtoverlay = strstr(fdtoverlay, " ")));
+}
+#endif
+
+/*
  * Boot according to the contents of a pxe_label.
  *
  * If we can't boot for any reason, we return.  A successful boot never
@@ -534,6 +625,11 @@ static int label_boot(struct cmd_tbl *cmdtp, struct pxe_label *label)
 					goto cleanup;
 				}
 			}
+
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+			if (label->fdtoverlays)
+				label_boot_fdtoverlay(cmdtp, label);
+#endif
 		} else {
 			bootm_argv[3] = NULL;
 		}
@@ -591,6 +687,7 @@ enum token_type {
 	T_INCLUDE,
 	T_FDT,
 	T_FDTDIR,
+	T_FDTOVERLAYS,
 	T_ONTIMEOUT,
 	T_IPAPPEND,
 	T_BACKGROUND,
@@ -625,6 +722,7 @@ static const struct token keywords[] = {
 	{"fdt", T_FDT},
 	{"devicetreedir", T_FDTDIR},
 	{"fdtdir", T_FDTDIR},
+	{"fdtoverlays", T_FDTOVERLAYS},
 	{"ontimeout", T_ONTIMEOUT,},
 	{"ipappend", T_IPAPPEND,},
 	{"background", T_BACKGROUND,},
@@ -1057,6 +1155,11 @@ static int parse_label(char **c, struct pxe_menu *cfg)
 				err = parse_sliteral(c, &label->fdtdir);
 			break;
 
+		case T_FDTOVERLAYS:
+			if (!label->fdtoverlays)
+				err = parse_sliteral(c, &label->fdtoverlays);
+			break;
+
 		case T_LOCALBOOT:
 			label->localboot = 1;
 			err = parse_integer(c, &label->localboot_val);
diff --git a/cmd/pxe_utils.h b/cmd/pxe_utils.h
index 77d25888758..6af95237343 100644
--- a/cmd/pxe_utils.h
+++ b/cmd/pxe_utils.h
@@ -43,6 +43,7 @@ struct pxe_label {
 	char *initrd;
 	char *fdt;
 	char *fdtdir;
+	char *fdtoverlays;
 	int ipappend;
 	int attempted;
 	int localboot;
diff --git a/doc/README.pxe b/doc/README.pxe
index 42f913c61fe..b67151ca510 100644
--- a/doc/README.pxe
+++ b/doc/README.pxe
@@ -89,6 +89,9 @@ pxe boot
      fdt_addr - the location of a fdt blob. 'fdt_addr' will be passed to bootm
      command if it is set and 'fdt_addr_r' is not passed to bootm command.
 
+     fdtoverlay_addr_r - location in RAM at which 'pxe boot' will temporarily store
+     fdt overlay(s) before applying them to the fdt blob stored at 'fdt_addr_r'.
+
 pxe file format
 ===============
 The pxe file format is nearly a subset of the PXELINUX file format; see
@@ -148,6 +151,12 @@ kernel <path>	    - if this label is chosen, use tftp to retrieve the kernel
 		      It useful for overlay selection in pxe file
 		      (see: doc/uImage.FIT/overlay-fdt-boot.txt)
 
+fdtoverlays <path> [...] - if this label is chosen, use tftp to retrieve the DT
+                      overlay(s) at <path>. it will be temporarily stored at the
+                      address indicated in the fdtoverlay_addr_r environment variable,
+                      and then applied in the load order to the fdt blob stored at the
+                      address indicated in the fdt_addr_r environment variable.
+
 append <string>	    - use <string> as the kernel command line when booting this
 		      label.