Add fuse API and commands

This can be useful for fuse-like hardware, OTP SoC options, etc.

Signed-off-by: Benoît Thébaudeau <[e-mail]>

README

···
 		CONFIG_CMD_FDOS		* Dos diskette Support
 		CONFIG_CMD_FLASH	  flinfo, erase, protect
 		CONFIG_CMD_FPGA		  FPGA device initialization support
+		CONFIG_CMD_FUSE		  Device fuse support
 		CONFIG_CMD_GETTIME	* Get time since boot
 		CONFIG_CMD_GO		* the 'go' command (exec code)
 		CONFIG_CMD_GREPENV	* search environment

common/Makefile

···
 COBJS-$(CONFIG_CMD_FPGA) += cmd_fpga.o
 endif
 COBJS-$(CONFIG_CMD_FS_GENERIC) += cmd_fs.o
+COBJS-$(CONFIG_CMD_FUSE) += cmd_fuse.o
 COBJS-$(CONFIG_CMD_GETTIME) += cmd_gettime.o
 COBJS-$(CONFIG_CMD_GPIO) += cmd_gpio.o
 COBJS-$(CONFIG_CMD_I2C) += cmd_i2c.o

common/cmd_fuse.c

···
+/*
+ * (C) Copyright 2009-2013 ADVANSEE
+ * Benoît Thébaudeau <[e-mail]>
+ *
+ * Based on the mpc512x iim code:
+ * Copyright 2008 Silicon Turnkey Express, Inc.
+ * Martha Marx <[e-mail]>
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <command.h>
+#include <fuse.h>
+#include <asm/errno.h>
+
+static int strtou32(const char *str, unsigned int base, u32 *result)
+{
+	char *ep;
+
+	*result = simple_strtoul(str, &ep, base);
+	if (ep == str || *ep != '\0')
+		return -EINVAL;
+
+	return 0;
+}
+
+static int confirm_prog(void)
+{
+	puts("Warning: Programming fuses is an irreversible operation!\n"
+			"         This may brick your system.\n"
+			"         Use this command only if you are sure of "
+					"what you are doing!\n"
+			"\nReally perform this fuse programming? <y/N>\n");
+
+	if (getc() == 'y') {
+		int c;
+
+		putc('y');
+		c = getc();
+		putc('\n');
+		if (c == '\r')
+			return 1;
+	}
+
+	puts("Fuse programming aborted\n");
+	return 0;
+}
+
+static int do_fuse(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
+{
+	const char *op = argc >= 2 ? argv[1] : NULL;
+	int confirmed = argc >= 3 && !strcmp(argv[2], "-y");
+	u32 bank, word, cnt, val;
+	int ret, i;
+
+	argc -= 2 + confirmed;
+	argv += 2 + confirmed;
+
+	if (argc < 2 || strtou32(argv[0], 0, &bank) ||
+			strtou32(argv[1], 0, &word))
+		return CMD_RET_USAGE;
+
+	if (!strcmp(op, "read")) {
+		if (argc == 2)
+			cnt = 1;
+		else if (argc != 3 || strtou32(argv[2], 0, &cnt))
+			return CMD_RET_USAGE;
+
+		printf("Reading bank %u:\n", bank);
+		for (i = 0; i < cnt; i++, word++) {
+			if (!(i % 4))
+				printf("\nWord 0x%.8x:", word);
+
+			ret = fuse_read(bank, word, &val);
+			if (ret)
+				goto err;
+
+			printf(" %.8x", val);
+		}
+		putc('\n');
+	} else if (!strcmp(op, "sense")) {
+		if (argc == 2)
+			cnt = 1;
+		else if (argc != 3 || strtou32(argv[2], 0, &cnt))
+			return CMD_RET_USAGE;
+
+		printf("Sensing bank %u:\n", bank);
+		for (i = 0; i < cnt; i++, word++) {
+			if (!(i % 4))
+				printf("\nWord 0x%.8x:", word);
+
+			ret = fuse_sense(bank, word, &val);
+			if (ret)
+				goto err;
+
+			printf(" %.8x", val);
+		}
+		putc('\n');
+	} else if (!strcmp(op, "prog")) {
+		if (argc < 3)
+			return CMD_RET_USAGE;
+
+		for (i = 2; i < argc; i++, word++) {
+			if (strtou32(argv[i], 16, &val))
+				return CMD_RET_USAGE;
+
+			printf("Programming bank %u word 0x%.8x to 0x%.8x...\n",
+					bank, word, val);
+			if (!confirmed && !confirm_prog())
+				return CMD_RET_FAILURE;
+			ret = fuse_prog(bank, word, val);
+			if (ret)
+				goto err;
+		}
+	} else if (!strcmp(op, "override")) {
+		if (argc < 3)
+			return CMD_RET_USAGE;
+
+		for (i = 2; i < argc; i++, word++) {
+			if (strtou32(argv[i], 16, &val))
+				return CMD_RET_USAGE;
+
+			printf("Overriding bank %u word 0x%.8x with "
+					"0x%.8x...\n", bank, word, val);
+			ret = fuse_override(bank, word, val);
+			if (ret)
+				goto err;
+		}
+	} else {
+		return CMD_RET_USAGE;
+	}
+
+	return 0;
+
+err:
+	puts("ERROR\n");
+	return ret;
+}
+
+U_BOOT_CMD(
+	fuse, CONFIG_SYS_MAXARGS, 0, do_fuse,
+	"Fuse sub-system",
+	     "read <bank> <word> [<cnt>] - read 1 or 'cnt' fuse words,\n"
+	"    starting at 'word'\n"
+	"fuse sense <bank> <word> [<cnt>] - sense 1 or 'cnt' fuse words,\n"
+	"    starting at 'word'\n"
+	"fuse prog [-y] <bank> <word> <hexval> [<hexval>...] - program 1 or\n"
+	"    several fuse words, starting at 'word' (PERMANENT)\n"
+	"fuse override <bank> <word> <hexval> [<hexval>...] - override 1 or\n"
+	"    several fuse words, starting at 'word'"
+);

doc/README.fuse

···
+Fuse API functions and commands
+
+The fuse API allows to control a fusebox and how it is used by the upper
+hardware layers.
+
+A fuse corresponds to a single non-volatile memory bit that can be programmed
+(i.e. blown, set to 1) only once. The programming operation is irreversible. A
+fuse that has not been programmed reads 0.
+
+Fuses can be used by SoCs to store various permanent configuration and data,
+e.g. boot configuration, security configuration, MAC addresses, etc.
+
+A fuse word is the smallest group of fuses that can be read at once from the
+fusebox control IP registers. This is limited to 32 bits with the current API.
+
+A fuse bank is the smallest group of fuse words having a common ID, as defined
+by each SoC.
+
+Upon startup, the fusebox control IP reads the fuse values and stores them to a
+volatile shadow cache.
+
+See the README files of the drivers implementing this API in order to know the
+SoC- and implementation-specific details.
+
+Functions / commands:
+
+   int fuse_read(u32 bank, u32 word, u32 *val);
+   fuse read <bank> <word> [<cnt>]
+      Read fuse words from the shadow cache.
+
+   int fuse_sense(u32 bank, u32 word, u32 *val);
+   fuse sense <bank> <word> [<cnt>]
+      Sense - i.e. read directly from the fusebox, skipping the shadow cache -
+      fuse words. This operation does not update the shadow cache.
+
+      This is useful to know the true value of fuses if an override has been
+      performed (see below).
+
+   int fuse_prog(u32 bank, u32 word, u32 val);
+   fuse prog [-y] <bank> <word> <hexval> [<hexval>...]
+      Program fuse words. This operation directly affects the fusebox and is
+      irreversible. The shadow cache is updated accordingly or not, depending on
+      each IP.
+
+      Only the bits to be programmed should be set in the input value (i.e. for
+      fuse bits that have already been programmed and hence should be left
+      unchanged by a further programming, it is preferable to clear the
+      corresponding bits in the input value in order not to perform a new
+      hardware programming operation on these fuse bits).
+
+   int fuse_override(u32 bank, u32 word, u32 val);
+   fuse override <bank> <word> <hexval> [<hexval>...]
+      Override fuse words in the shadow cache.
+
+      The fusebox is unaffected, so following this operation, the shadow cache
+      may differ from the fusebox values. Read or sense operations can then be
+      used to get the values from the shadow cache or from the fusebox.
+
+      This is useful to change the behaviors linked to some cached fuse values,
+      either because this is needed only temporarily, or because some of the
+      fuses have already been programmed or are locked (if the SoC allows to
+      override a locked fuse).
+
+Configuration:
+
+   CONFIG_CMD_FUSE
+      Define this to enable the fuse commands.

include/config_cmd_all.h

···
 #define CONFIG_CMD_FDOS		/* Floppy DOS support		*/
 #define CONFIG_CMD_FLASH	/* flinfo, erase, protect	*/
 #define CONFIG_CMD_FPGA		/* FPGA configuration Support	*/
+#define CONFIG_CMD_FUSE		/* Device fuse support		*/
 #define CONFIG_CMD_GETTIME	/* Get time since boot         */
 #define CONFIG_CMD_HASH		/* calculate hash / digest	*/
 #define CONFIG_CMD_HWFLOW	/* RTS/CTS hw flow control	*/

include/fuse.h

···
+/*
+ * (C) Copyright 2009-2013 ADVANSEE
+ * Benoît Thébaudeau <[e-mail]>
+ *
+ * Based on the mpc512x iim code:
+ * Copyright 2008 Silicon Turnkey Express, Inc.
+ * Martha Marx <[e-mail]>
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef _FUSE_H_
+#define _FUSE_H_
+
+/*
+ * Read/Sense/Program/Override interface:
+ *   bank:    Fuse bank
+ *   word:    Fuse word within the bank
+ *   val:     Value to read/write
+ *
+ *   Returns: 0 on success, not 0 on failure
+ */
+int fuse_read(u32 bank, u32 word, u32 *val);
+int fuse_sense(u32 bank, u32 word, u32 *val);
+int fuse_prog(u32 bank, u32 word, u32 val);
+int fuse_override(u32 bank, u32 word, u32 val);
+
+#endif	/* _FUSE_H_ */