ec/google/common: Add a common MEC interface

In order to re-use the MEC interface code in the Chrome EC driver
move it to a common directory within the ec/google directory.

The Chrome EC driver itself is changed to use this interface in the
next commit, and future commits will introduce a new EC that also
uses this interface.

Change-Id: I13516b5e4c4c49f53bb998366284a26703142e2a
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: https://review.coreboot.org/29111
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

4 files changed, 174 insertions, 0 deletions

diff --git a/src/ec/google/common/Kconfig b/src/ec/google/common/Kconfig
new file mode 100644
index 000000000000..2e138a555fda
--- /dev/null
+++ b/src/ec/google/common/Kconfig
@@ -0,0 +1,4 @@
+config EC_GOOGLE_COMMON_MEC
+	bool
+	help
+	  Google common EC functions for Microchip EMI region.
diff --git a/src/ec/google/common/Makefile.inc b/src/ec/google/common/Makefile.inc
new file mode 100644
index 000000000000..7ab2285ac69e
--- /dev/null
+++ b/src/ec/google/common/Makefile.inc
@@ -0,0 +1,5 @@
+bootblock-$(CONFIG_EC_GOOGLE_COMMON_MEC) += mec.c
+verstage-$(CONFIG_EC_GOOGLE_COMMON_MEC) += mec.c
+romstage-$(CONFIG_EC_GOOGLE_COMMON_MEC) += mec.c
+ramstage-$(CONFIG_EC_GOOGLE_COMMON_MEC) += mec.c
+smm-$(CONFIG_EC_GOOGLE_COMMON_MEC) += mec.c
diff --git a/src/ec/google/common/mec.c b/src/ec/google/common/mec.c
new file mode 100644
index 000000000000..06a6bca5530f
--- /dev/null
+++ b/src/ec/google/common/mec.c
@@ -0,0 +1,122 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google LLC
+ *
+ * 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; version 2 of the License
+ *
+ * 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.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <arch/io.h>
+
+#include "mec.h"
+
+enum mec_access_mode {
+	/* 8-bit access */
+	ACCESS_TYPE_BYTE = 0x0,
+	/* 16-bit access */
+	ACCESS_TYPE_WORD = 0x1,
+	/* 32-bit access */
+	ACCESS_TYPE_LONG = 0x2,
+	/*
+	 * 32-bit access, read or write of MEC_EMI_EC_DATA_B3 causes the
+	 * EC data register to be incremented.
+	 */
+	ACCESS_TYPE_LONG_AUTO_INCREMENT = 0x3,
+};
+
+/* EMI registers are relative to base */
+#define MEC_EMI_HOST_TO_EC(base)	((base) + 0)
+#define MEC_EMI_EC_TO_HOST(base)	((base) + 1)
+#define MEC_EMI_EC_ADDRESS_B0(base)	((base) + 2)
+#define MEC_EMI_EC_ADDRESS_B1(base)	((base) + 3)
+#define MEC_EMI_EC_DATA_B0(base)	((base) + 4)
+#define MEC_EMI_EC_DATA_B1(base)	((base) + 5)
+#define MEC_EMI_EC_DATA_B2(base)	((base) + 6)
+#define MEC_EMI_EC_DATA_B3(base)	((base) + 7)
+
+/*
+ * cros_ec_lpc_mec_emi_write_address
+ *
+ * Initialize EMI read / write at a given address.
+ *
+ * @base:        Starting read / write address
+ * @offset:      Offset applied to base address
+ * @access_mode: Type of access, typically 32-bit auto-increment
+ */
+static void mec_emi_write_address(uint16_t base, uint16_t offset,
+				  enum mec_access_mode access_mode)
+{
+	outb((offset & 0xfc) | access_mode, MEC_EMI_EC_ADDRESS_B0(base));
+	outb((offset >> 8) & 0x7f, MEC_EMI_EC_ADDRESS_B1(base));
+}
+
+uint8_t mec_io_bytes(enum mec_io_type type, uint16_t base,
+		     uint16_t offset, void *buffer, size_t size)
+{
+	enum mec_access_mode access_mode, new_access_mode;
+	uint8_t *buf = buffer;
+	uint8_t checksum = 0;
+	int io_addr;
+	int i = 0;
+
+	if (size == 0 || base == 0)
+		return 0;
+
+	/*
+	 * Long access cannot be used on misaligned data since reading B0 loads
+	 * the data register and writing B3 flushes it.
+	 */
+	if ((offset & 0x3) || (size < 4))
+		access_mode = ACCESS_TYPE_BYTE;
+	else
+		access_mode = ACCESS_TYPE_LONG_AUTO_INCREMENT;
+
+	/* Initialize I/O at desired address */
+	mec_emi_write_address(base, offset, access_mode);
+
+	/* Skip bytes in case of misaligned offset */
+	io_addr = MEC_EMI_EC_DATA_B0(base) + (offset & 0x3);
+	while (i < size) {
+		while (io_addr <= MEC_EMI_EC_DATA_B3(base)) {
+			if (type == MEC_IO_WRITE)
+				outb(buf[i], io_addr++);
+			else
+				buf[i] = inb(io_addr++);
+
+			checksum += buf[i++];
+			offset++;
+
+			/* Extra bounds check in case of misaligned size */
+			if (i == size)
+				return checksum;
+		}
+
+		/*
+		 * Use long auto-increment access except for misaligned write,
+		 * since writing B3 triggers the flush.
+		 */
+		if ((size - i) < 4 && type == MEC_IO_WRITE)
+			new_access_mode = ACCESS_TYPE_BYTE;
+		else
+			new_access_mode = ACCESS_TYPE_LONG_AUTO_INCREMENT;
+		if (new_access_mode != access_mode ||
+		    access_mode != ACCESS_TYPE_LONG_AUTO_INCREMENT) {
+			access_mode = new_access_mode;
+			mec_emi_write_address(base, offset, access_mode);
+		}
+
+		/* Access [B0, B3] on each loop pass */
+		io_addr = MEC_EMI_EC_DATA_B0(base);
+	}
+
+	return checksum;
+}
diff --git a/src/ec/google/common/mec.h b/src/ec/google/common/mec.h
new file mode 100644
index 000000000000..3452bada7a99
--- /dev/null
+++ b/src/ec/google/common/mec.h
@@ -0,0 +1,43 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google LLC
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.
+ */
+
+#ifndef EC_GOOGLE_COMMON_MEC_H
+#define EC_GOOGLE_COMMON_MEC_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* Indicate read or write from MEC IO region */
+enum mec_io_type {
+	MEC_IO_READ,
+	MEC_IO_WRITE
+};
+
+/*
+ * mec_io_bytes - Read / write bytes to MEC EMI port
+ *
+ * @type:    Indicate read or write operation
+ * @base:    Base address for MEC EMI region
+ * @offset:  Base read / write address
+ * @buffer:  Destination / source buffer
+ * @size:    Number of bytes to read / write
+ *
+ * @returns 8-bit checksum of all bytes read or written
+ */
+
+uint8_t mec_io_bytes(enum mec_io_type type, uint16_t base,
+		     uint16_t offset, void *buffer, size_t size);
+
+#endif /* EC_GOOGLE_COMMON_MEC_H */