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 <[email protected]>
Cc: Andre Heider <[email protected]>
Cc: Jernej Škrabec <[email protected]>
Cc: Jonas Karlman <[email protected]>
Tested-by: Jernej Škrabec <[email protected]>
Reviewed-by: Jernej Škrabec <[email protected]>
Signed-off-by: Neil Armstrong <[email protected]>

The original commit is
u-boot/u-boot@69076df

Signed-off-by: Stephen Chen <[email protected]>

Author: RadxaStephen

cmd/pxe.c

@@ -9,6 +9,8 @@
 #include <command.h>
 #include <malloc.h>
 #include <mapmem.h>
+#include <fdt_support.h>
+#include <linux/libfdt.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <errno.h>
@@ -476,6 +478,7 @@ struct pxe_label {
 	char *initrd;
 	char *fdt;
 	char *fdtdir;
+	char *fdtoverlays;
 	int ipappend;
 	int attempted;
 	int localboot;
@@ -551,6 +554,9 @@ static void label_destroy(struct pxe_label *label)
 	if (label->fdtdir)
 		free(label->fdtdir);
 
+	if (label->fdtoverlays)
+		free(label->fdtoverlays);
+
 	free(label);
 }
 
@@ -598,6 +604,92 @@ static int label_localboot(struct pxe_label *label)
 	return run_command_list(localcmd, strlen(localcmd), 0);
 }
 
+/*
+ * Loads fdt overlays specified in 'fdtoverlays'.
+ */
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+static void label_boot_fdtoverlay(cmd_tbl_t *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.
  *
@@ -775,6 +867,11 @@ static int label_boot(cmd_tbl_t *cmdtp, struct pxe_label *label)
 						label->name);
 				return 1;
 			}
+
+#ifdef CONFIG_OF_LIBFDT_OVERLAY
+			if (label->fdtoverlays)
+				label_boot_fdtoverlay(cmdtp, label);
+#endif
 		} else {
 			bootm_argv[3] = NULL;
 		}
@@ -828,6 +925,7 @@ enum token_type {
 	T_INCLUDE,
 	T_FDT,
 	T_FDTDIR,
+	T_FDTOVERLAYS,
 	T_ONTIMEOUT,
 	T_IPAPPEND,
 	T_INVALID
@@ -861,6 +959,7 @@ static const struct token keywords[] = {
 	{"fdt", T_FDT},
 	{"devicetreedir", T_FDTDIR},
 	{"fdtdir", T_FDTDIR},
+	{"fdtoverlays", T_FDTOVERLAYS},
 	{"ontimeout", T_ONTIMEOUT,},
 	{"ipappend", T_IPAPPEND,},
 	{NULL, T_INVALID}
@@ -1262,6 +1361,11 @@ 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);

doc/README.pxe

@@ -90,6 +90,9 @@ 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
@@ -142,6 +145,12 @@ kernel <path>	    - if this label is chosen, use tftp to retrieve the kernel
 		      indicated in the kernel_addr_r environment variable, and
 		      that address will be passed to bootm to boot this kernel.
 
+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.