armv8: semihosting: add a command to load semihosted images

Instead of sprinkling custom code and calls over the Vexpress64
boardfile, create a command that loads images using semihosting
just like we would load from flash memory of over the network,
using a special command:

    smhload <image> <address>

This will make it possible to remove some custom calls and
code and make the boot easier.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/lib/semihosting.c

@@ -13,6 +13,7 @@
  * for them.
  */
 #include <common.h>
+#include <command.h>
 #include <asm/semihosting.h>
 
 #define SYSOPEN		0x01
@@ -234,3 +235,72 @@ long smh_len(const char *fname)
 	/* Return the file length (or -1 error indication) */
 	return len;
 }
+
+static int smh_load_file(const char * const name, ulong load_addr,
+			 ulong *end_addr)
+{
+	long fd;
+	long len;
+	long ret;
+
+	fd = smh_open(name, "rb");
+	if (fd == -1)
+		return -1;
+
+	len = smh_len_fd(fd);
+	if (len < 0) {
+		smh_close(fd);
+		return -1;
+	}
+
+	ret = smh_read(fd, (void *)load_addr, len);
+	smh_close(fd);
+
+	if (ret == 0) {
+		*end_addr = load_addr + len - 1;
+		printf("loaded file %s from %08lX to %08lX, %08lX bytes\n",
+		       name,
+		       load_addr,
+		       *end_addr,
+		       len);
+	} else {
+		printf("read failed\n");
+		return 0;
+	}
+
+	return 0;
+}
+
+static int do_smhload(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	if (argc == 3 || argc == 4) {
+		ulong load_addr;
+		ulong end_addr = 0;
+		ulong ret;
+		char end_str[64];
+
+		load_addr = simple_strtoul(argv[2], NULL, 16);
+		if (!load_addr)
+			return -1;
+
+		ret = smh_load_file(argv[1], load_addr, &end_addr);
+		if (ret < 0)
+			return 1;
+
+		/* Optionally save returned end to the environment */
+		if (argc == 4) {
+			sprintf(end_str, "0x%08lx", end_addr);
+			setenv(argv[3], end_str);
+		}
+	} else {
+		return CMD_RET_USAGE;
+	}
+	return 0;
+}
+
+U_BOOT_CMD(smhload, 4, 0, do_smhload, "load a file using semihosting",
+	   "<file> 0x<address> [end var]\n"
+	   "    - load a semihosted file to the address specified\n"
+	   "      if the optional [end var] is specified, the end\n"
+	   "      address of the file will be stored in this environment\n"
+	   "      variable.\n");

doc/README.semihosting

@@ -30,25 +30,10 @@ vexpress_aemv8a.h but differentiate the two models by the presence or
 absence of CONFIG_BASE_FVP. This change is tested and works on both the
 Foundation and Base fastmodel simulators.
 
-The level of semihosting support is minimal, restricted to just what it
-takes to load images to memory. If more semihosting functionality is
-required, such as file seek, outputting strings, reading characters, etc,
-then it can be easily added later.
+The semihosting code adds a command:
 
-We require that the board include file define these env variables:
-- kernel_name		e.g. "uImage"
-- kernel_addr_r		e.g. "0x80000000"
-- initrd_name		e.g. "ramdisk.img"
-- initrd_addr_r		e.g. "0x88000000"
-- fdt_name		e.g. "devtree.dtb"
-- fdt_addr_r		e.g. "0x83000000"
+  smhload <image> <address> [env var]
 
-Optionally, "fdt_high" and "initrd_high" can be specified as per
-their rules for allowing or preventing copying of these images.
-
-For the "fdt chosen" startup macro, this code will then define:
-- initrd_end (based on retrieving initrd_addr_r plus actual initrd_size)
-
-We will then load the kernel, initrd, and fdt into the specified
-locations in memory in a similar way that the ATF fastmodel code
-uses semihosting calls to load other boot stages and u-boot itself.
+That will load an image from the host filesystem into RAM at the specified
+address and optionally store the load end address in the specified
+environment variable.