[coreboot-gerrit] Change in coreboot[master]: ec: Add support for MEC5055 for Dell laptops

[Iru Cai (vimacs) (Code Review)]

Hello Iru Cai,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/coreboot/+/44975

to review the following change.

Change subject: ec: Add support for MEC5055 for Dell laptops
......................................................................

ec: Add support for MEC5055 for Dell laptops

This EC support code is required to boot various Dell Latitude laptops,
otherwise the laptop will shut down in a minute after powered on.

Tested on Dell Latitude E7240.

Change-Id: Iee68ea52dcf0242315868a46b5e4768303e30dce
Signed-off-by: Iru Cai 
---
A src/ec/dell/mec5055/Kconfig
A src/ec/dell/mec5055/Makefile.inc
A src/ec/dell/mec5055/early_init.c
A src/ec/dell/mec5055/mec5055.c
A src/ec/dell/mec5055/mec5055.h
5 files changed, 148 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/75/44975/1

diff --git a/src/ec/dell/mec5055/Kconfig b/src/ec/dell/mec5055/Kconfig
new file mode 100644
index 0000000..a7bf9a5
--- /dev/null
+++ b/src/ec/dell/mec5055/Kconfig
@@ -0,0 +1,4 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+config EC_DELL_MEC5055
+	bool
diff --git a/src/ec/dell/mec5055/Makefile.inc b/src/ec/dell/mec5055/Makefile.inc
new file mode 100644
index 0000000..9cdfbb3
--- /dev/null
+++ b/src/ec/dell/mec5055/Makefile.inc
@@ -0,0 +1,8 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+ifeq ($(CONFIG_EC_DELL_MEC5055),y)
+
+bootblock-y += mec5055.c early_init.c
+romstage-y += mec5055.c early_init.c
+
+endif
diff --git a/src/ec/dell/mec5055/early_init.c b/src/ec/dell/mec5055/early_init.c
new file mode 100644
index 0000000..6aec48b
--- /dev/null
+++ b/src/ec/dell/mec5055/early_init.c
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#include "mec5055.h"
+
+void mec5055_early_init(void)
+{
+	u8 buf[32], c;
+
+	mec5055_ec_command_0(buf, 0xc2, 0);
+	mec5055_ec_command_1(0xab, NULL, 0, &c, 1);
+}
diff --git a/src/ec/dell/mec5055/mec5055.c b/src/ec/dell/mec5055/mec5055.c
new file mode 100644
index 0000000..2deec7d
--- /dev/null
+++ b/src/ec/dell/mec5055/mec5055.c
@@ -0,0 +1,110 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#include <arch/io.h>
+#include "mec5055.h"
+
+static const u16 EC_CTRL = 0x910;
+static const u16 EC_DATA = 0x911;
+
+static void wait_ec(void)
+{
+	u8 v;
+	do {
+		outb(0, EC_CTRL);
+		v = inb(EC_DATA);
+	} while (v != 0);
+}
+
+static int read_ec_regs(u8 start, u8 *sdata, u8 count)
+{
+	if (start >= 0x20 || start + count > 0x20)
+		return -1;
+
+	if (count <= 0)
+		return 0;
+
+	while (count--) {
+		outb(start + 0x10, EC_CTRL);
+		*sdata = inb(EC_DATA);
+		sdata++;
+		start++;
+	}
+
+	return 0;
+}
+
+static int write_ec_regs(u8 start, const u8 *sdata, u8 count)
+{
+	if (start >= 0x20 || start + count > 0x20)
+		return -1;
+
+	if (count <= 0)
+		return 0;
+
+	while (count--) {
+		outb(start + 0x10, EC_CTRL);
+		outb(*sdata, EC_DATA);
+		sdata++;
+		start++;
+	}
+
+	return 0;
+}
+
+/* Steps to communicate with the EC:
+ * 1. send command:
+ *   - write arguments to EC[2:]
+ *   - send 0 to CTRL then cmd to DATA
+ * 2. wait EC
+ * 3. receive result: result may starts at EC[0] or EC[1]
+ */
+
+/* send command to EC and wait, command at cmd[0], args in cmd[2:] */
+static int ec_send_command(const u8 *cmd, int argc)
+{
+	int result = 0;
+
+	if (argc > 0) {
+		if (argc > 0x1e)
+			result = -1;
+		else
+			result = write_ec_regs(2, cmd + 2, argc);
+	}
+
+	outb(0, EC_CTRL);
+	outb(cmd[0], EC_DATA);
+	wait_ec();
+	return result;
+}
+
+/* receive result from EC[0:] */
+int mec5055_ec_command_0(u8 *buf, u8 cmd, int argc)
+{
+	buf[0] = cmd;
+	int res = ec_send_command(buf, argc);
+	if (res < 0)
+		return res;
+
+	return read_ec_regs(0, buf, 0x10);
+}
+
+/* receive result from EC[1:] */
+int mec5055_ec_command_1(u8 cmd, const u8 *cmd_buf, int argc, u8 *res_buf, int res_size)
+{
+	if (argc >= 0x1e)
+		argc = 0x1e;
+
+	if (res_size >= 0x1f)
+		res_size = 0x1f;
+
+	int t = write_ec_regs(2, cmd_buf, argc);
+	if (t < 0)
+		return t;
+
+	outb(0, EC_CTRL);
+	outb(cmd, EC_DATA);
+	wait_ec();
+
+	return read_ec_regs(1, res_buf, res_size);
+}
diff --git a/src/ec/dell/mec5055/mec5055.h b/src/ec/dell/mec5055/mec5055.h
new file mode 100644
index 0000000..33c6a1d
--- /dev/null
+++ b/src/ec/dell/mec5055/mec5055.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#ifndef _EC_DELL_MEC5055_H_
+#define _EC_DELL_MEC5055_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+int mec5055_ec_command_0(u8 *buf, u8 cmd, int argc);
+int mec5055_ec_command_1(u8 cmd, const u8 *cmd_buf, int argc, u8 *res_buf, int res_size);
+void mec5055_early_init(void);
+
+#endif