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 being powered on.

Tested on Dell Latitude E7240.

Change-Id: Iee68ea52dcf0242315868a46b5e4768303e30dce
Signed-off-by: Iru Cai <mytbk920423@gmail.com>

1 files changed, 115 insertions, 0 deletions

diff --git a/src/ec/dell/mec5055/mec5055.c b/src/ec/dell/mec5055/mec5055.c
new file mode 100644
index 0000000000..4e41229a13
--- /dev/null
+++ b/src/ec/dell/mec5055/mec5055.c
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <arch/io.h>
+#include <console/console.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 enum cb_err read_ec_regs(u8 start, u8 *sdata, u8 count)
+{
+	if (start >= 0x20 || start + count > 0x20) {
+		printk(BIOS_ERR, "%s: Invalid start or count argument.\n", __func__);
+		return CB_ERR_ARG;
+	}
+
+	while (count--) {
+		outb(start + 0x10, EC_CTRL);
+		*sdata = inb(EC_DATA);
+		sdata++;
+		start++;
+	}
+
+	return CB_SUCCESS;
+}
+
+static enum cb_err write_ec_regs(u8 start, const u8 *sdata, u8 count)
+{
+	if (start >= 0x20 || start + count > 0x20) {
+		printk(BIOS_ERR, "%s: Invalid start or count argument.\n", __func__);
+		return CB_ERR_ARG;
+	}
+
+	while (count--) {
+		outb(start + 0x10, EC_CTRL);
+		outb(*sdata, EC_DATA);
+		sdata++;
+		start++;
+	}
+
+	return CB_SUCCESS;
+}
+
+/*
+ * Steps to communicate with the EC:
+ * 1. send command:
+ *   - write arguments to EC[2:]
+ *   - send 0 to CTRL then cmd to DATA
+ * 2. wait for 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 enum cb_err ec_send_command(const u8 *cmd, int argc)
+{
+	int result = CB_SUCCESS;
+
+	if (argc > 0) {
+		if (argc > 0x1e) {
+			printk(BIOS_ERR, "%s: argc too big.\n", __func__);
+			result = CB_ERR_ARG;
+		} 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:] */
+enum cb_err mec5055_ec_command_0(u8 *buf, u8 cmd, int argc)
+{
+	buf[0] = cmd;
+	enum cb_err res = ec_send_command(buf, argc);
+	if (res != CB_SUCCESS) {
+		printk(BIOS_ERR, "error: %s returns %d.\n", __func__, res);
+		return res;
+	}
+
+	return read_ec_regs(0, buf, 0x10);
+}
+
+/* receive result from EC[1:] */
+enum cb_err 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;
+
+	enum cb_err res = write_ec_regs(2, cmd_buf, argc);
+	if (res != CB_SUCCESS) {
+		printk(BIOS_ERR, "error: %s returns %d.\n", __func__, res);
+		return res;
+	}
+
+	outb(0, EC_CTRL);
+	outb(cmd, EC_DATA);
+	wait_ec();
+
+	return read_ec_regs(1, res_buf, res_size);
+}