U-Boot

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2014 Google, Inc
 */

#include <command.h>
#include <log.h>
#include <vsprintf.h>
#include <linux/string.h>
#include <asm/msr.h>
#include <asm/mp.h>
#include <asm/mtrr.h>

static int do_mtrr_set(int cpu_select, uint reg, int argc, char *const argv[])
{
	const char *typename = argv[0];
	u64 start, size;
	u64 base, mask;
	int type = -1;
	bool valid;
	int ret;

	if (argc < 3)
		return CMD_RET_USAGE;
	type = mtrr_get_type_by_name(typename);
	if (type < 0) {
		printf("Invalid type name %s\n", typename);
		return CMD_RET_USAGE;
	}
	start = hextoull(argv[1], NULL);
	size = hextoull(argv[2], NULL);

	base = start | type;
	valid = native_read_msr(MTRR_PHYS_MASK_MSR(reg)) & MTRR_PHYS_MASK_VALID;
	mask = mtrr_to_mask(size);
	if (valid)
		mask |= MTRR_PHYS_MASK_VALID;

	ret = mtrr_set(cpu_select, reg, base, mask);
	if (ret)
		return CMD_RET_FAILURE;

	return 0;
}

static int do_mtrr(struct cmd_tbl *cmdtp, int flag, int argc,
		   char *const argv[])
{
	int reg_count = mtrr_get_var_count();
	int cmd;
	int cpu_select;
	uint reg;
	int ret;

	cpu_select = MP_SELECT_BSP;
	if (argc >= 3 && !strcmp("-c", argv[1])) {
		const char *cpustr;

		cpustr = argv[2];
		if (*cpustr == 'a')
			cpu_select = MP_SELECT_ALL;
		else
			cpu_select = simple_strtol(cpustr, NULL, 16);
		argc -= 2;
		argv += 2;
	}
	argc--;
	argv++;
	cmd = argv[0] ? *argv[0] : 0;
	if (argc < 1 || !cmd) {
		cmd = 'l';
		reg = 0;
	}
	if (cmd != 'l') {
		if (argc < 2)
			return CMD_RET_USAGE;
		reg = hextoul(argv[1], NULL);
		if (reg >= reg_count) {
			printf("Invalid register number\n");
			return CMD_RET_USAGE;
		}
	}
	if (cmd == 'l') {
		bool first;
		int i;

		i = mp_first_cpu(cpu_select);
		if (i < 0) {
			printf("Invalid CPU (err=%d)\n", i);
			return CMD_RET_FAILURE;
		}
		first = true;
		for (; i >= 0; i = mp_next_cpu(cpu_select, i)) {
			if (!first)
				printf("\n");
			printf("CPU %d:\n", i);
			ret = mtrr_list(reg_count, i);
			if (ret) {
				printf("Failed to read CPU %s (err=%d)\n",
				       i < MP_SELECT_ALL ? simple_itoa(i) : "",
				       ret);
				return CMD_RET_FAILURE;
			}
			first = false;
		}
	} else {
		switch (cmd) {
		case 'e':
			ret = mtrr_set_valid(cpu_select, reg, true);
			break;
		case 'd':
			ret = mtrr_set_valid(cpu_select, reg, false);
			break;
		case 's':
			ret = do_mtrr_set(cpu_select, reg, argc - 2, argv + 2);
			break;
		default:
			return CMD_RET_USAGE;
		}
		if (ret) {
			printf("Operation failed (err=%d)\n", ret);
			return CMD_RET_FAILURE;
		}
	}

	return 0;
}

U_BOOT_CMD(
	mtrr,	8,	1,	do_mtrr,
	"Use x86 memory type range registers (32-bit only)",
	"[list]        - list current registers\n"
	"set <reg> <type> <start> <size>   - set a register\n"
	"\t<type> is Uncacheable, Combine, Through, Protect, Back\n"
	"disable <reg>      - disable a register\n"
	"enable <reg>       - enable a register\n"
	"\n"
	"Precede command with '-c <n>|all' to access a particular hex CPU, e.g.\n"
	"   mtrr -c all list; mtrr -c 2e list"
);