x86: Add an 'mtrr' command to list and adjust MTRRs

It is useful to be able to see the MTRR setup in U-Boot. Add a command
to list the state of the variable MTRR registers and allow them to be
changed.

Update the documentation to list some of the available commands.

This does not support fixed MTRRs as yet.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/lib/Makefile

@@ -14,6 +14,7 @@ obj-$(CONFIG_HAVE_FSP) += cmd_hob.o
 obj-y	+= gcc.o
 obj-y	+= init_helpers.o
 obj-y	+= interrupts.o
+obj-y += cmd_mtrr.o
 obj-$(CONFIG_SYS_PCAT_INTERRUPTS) += pcat_interrupts.o
 obj-$(CONFIG_SYS_PCAT_TIMER) += pcat_timer.o
 obj-$(CONFIG_PCI) += pci_type1.o

arch/x86/lib/cmd_mtrr.c

+/*
+ * (C) Copyright 2014 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <asm/msr.h>
+#include <asm/mtrr.h>
+
+static const char *const mtrr_type_name[MTRR_TYPE_COUNT] = {
+	"Uncacheable",
+	"Combine",
+	"2",
+	"3",
+	"Through",
+	"Protect",
+	"Back",
+};
+
+static int do_mtrr_list(void)
+{
+	int i;
+
+	printf("Reg Valid Write-type   %-16s %-16s %-16s\n", "Base   ||",
+	       "Mask   ||", "Size   ||");
+	for (i = 0; i < MTRR_COUNT; i++) {
+		const char *type = "Invalid";
+		uint64_t base, mask, size;
+		bool valid;
+
+		base = native_read_msr(MTRR_PHYS_BASE_MSR(i));
+		mask = native_read_msr(MTRR_PHYS_MASK_MSR(i));
+		size = ~mask & ((1ULL << CONFIG_CPU_ADDR_BITS) - 1);
+		size |= (1 << 12) - 1;
+		size += 1;
+		valid = mask & MTRR_PHYS_MASK_VALID;
+		type = mtrr_type_name[base & MTRR_BASE_TYPE_MASK];
+		printf("%d   %-5s %-12s %016llx %016llx %016llx\n", i,
+		       valid ? "Y" : "N", type, base, mask, size);
+	}
+
+	return 0;
+}
+
+static int do_mtrr_set(uint reg, int argc, char * const argv[])
+{
+	const char *typename = argv[0];
+	struct mtrr_state state;
+	uint32_t start, size;
+	uint64_t base, mask;
+	int i, type = -1;
+	bool valid;
+
+	if (argc < 3)
+		return CMD_RET_USAGE;
+	for (i = 0; i < MTRR_TYPE_COUNT; i++) {
+		if (*typename == *mtrr_type_name[i])
+			type = i;
+	}
+	if (type == -1) {
+		printf("Invalid type name %s\n", typename);
+		return CMD_RET_USAGE;
+	}
+	start = simple_strtoul(argv[1], NULL, 16);
+	size = simple_strtoul(argv[2], NULL, 16);
+
+	base = start | type;
+	valid = native_read_msr(MTRR_PHYS_MASK_MSR(reg)) & MTRR_PHYS_MASK_VALID;
+	mask = ~((uint64_t)size - 1);
+	mask &= (1ULL << CONFIG_CPU_ADDR_BITS) - 1;
+	if (valid)
+		mask |= MTRR_PHYS_MASK_VALID;
+
+	printf("base=%llx, mask=%llx\n", base, mask);
+	mtrr_open(&state);
+	wrmsrl(MTRR_PHYS_BASE_MSR(reg), base);
+	wrmsrl(MTRR_PHYS_MASK_MSR(reg), mask);
+	mtrr_close(&state);
+
+	return 0;
+}
+
+static int mtrr_set_valid(int reg, bool valid)
+{
+	struct mtrr_state state;
+	uint64_t mask;
+
+	mtrr_open(&state);
+	mask = native_read_msr(MTRR_PHYS_MASK_MSR(reg));
+	if (valid)
+		mask |= MTRR_PHYS_MASK_VALID;
+	else
+		mask &= ~MTRR_PHYS_MASK_VALID;
+	wrmsrl(MTRR_PHYS_MASK_MSR(reg), mask);
+	mtrr_close(&state);
+
+	return 0;
+}
+
+static int do_mtrr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	const char *cmd;
+	uint reg;
+
+	cmd = argv[1];
+	if (argc < 2 || *cmd == 'l')
+		return do_mtrr_list();
+	argc -= 2;
+	argv += 2;
+	if (argc <= 0)
+		return CMD_RET_USAGE;
+	reg = simple_strtoul(argv[0], NULL, 16);
+	if (reg >= MTRR_COUNT) {
+		printf("Invalid register number\n");
+		return CMD_RET_USAGE;
+	}
+	if (*cmd == 'e')
+		return mtrr_set_valid(reg, true);
+	else if (*cmd == 'd')
+		return mtrr_set_valid(reg, false);
+	else if (*cmd == 's')
+		return do_mtrr_set(reg, argc - 1, argv + 1);
+	else
+		return CMD_RET_USAGE;
+
+	return 0;
+}
+
+U_BOOT_CMD(
+	mtrr,	6,	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"
+	"ensable <reg>      - enable a register"
+);

doc/README.x86

@@ -110,9 +110,25 @@ be turned on. Not every device on the board is configured via devie tree, but
 more and more devices will be added as time goes by. Check out the directory
 arch/x86/dts/ for these device tree source files.
 
+Useful Commands
+---------------
+
+In keeping with the U-Boot philosophy of providing functions to check and
+adjust internal settings, there are several x86-specific commands that may be
+useful:
+
+hob  - Display information about Firmware Support Package (FSP) Hand-off
+	 Block. This is only available on platforms which use FSP, mostly
+	 Atom.
+iod  - Display I/O memory
+iow  - Write I/O memory
+mtrr - List and set the Memory Type Range Registers (MTRR). These are used to
+	 tell the CPU whether memory is cacheable and if so the cache write
+	 mode to use. U-Boot sets up some reasonable values but you can
+	 adjust then with this command.
+
 TODO List
 ---------
-- MTRR support (for performance)
 - Audio
 - Chrome OS verified boot
 - SMI and ACPI support, to provide platform info and facilities to Linux