ec/lenovo/h8: Add function to query sense state

* Add function to wait for sense registers to become valid.
* Add function to retrieve Fn-Key state.

Tested on Lenovo T500:
* It takes about 700msec for the registers to become valid.

Tested on Lenovo T520:
* It takes less than 150msec for the registers to become valid.

Change-Id: Ie27e2881a256c4efb3def11f05070c446db6e5fc
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/29204
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/ec/lenovo/h8/Makefile.inc

@@ -1,5 +1,12 @@
 ifeq ($(CONFIG_EC_LENOVO_H8),y)
 
+ramstage-y += sense.c
+verstage-y += sense.c
+romstage-y += sense.c
+bootblock-y += sense.c
+postcar-y += sense.c
+smm-y += sense.c
+
 ifneq ($(filter y,$(CONFIG_H8_BEEP_ON_DEATH) $(CONFIG_H8_FLASH_LEDS_ON_DEATH)),)
 romstage-y += panic.c
 ramstage-y += panic.c

src/ec/lenovo/h8/h8.h

@@ -38,6 +38,9 @@ void h8_usb_always_on(void);
 
 void h8_mainboard_init_dock (void);
 
+int h8_get_fn_key(void);
+int h8_get_sense_ready(void);
+
 void h8_bluetooth_enable(int on);
 bool h8_bluetooth_nv_enable(void);
 bool h8_has_bdc(struct device *dev);
@@ -135,8 +138,10 @@ void h8_ssdt_generator(struct device *dev);
 #define H8_EVENT_FN_PRESS	0x39
 
 #define H8_STATUS0		0x46
+#define H8_STATUS0_FN_KEY_DOWN	0x01
 #define H8_STATUS1		0x47
 #define H8_STATUS2		0x48
+#define H8_STATUS3		0x49
 
 #define H8_EVENT_BAT0		0x4a
 #define H8_EVENT_BAT0_STATE	0x4b

src/ec/lenovo/h8/sense.c

@@ -0,0 +1,54 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2018 Patrick Rudolph <siro@das-labor.org>
+ *
+ * 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 <ec/acpi/ec.h>
+
+#include "h8.h"
+
+/**
+ * Return the EC sense status register state.
+ *
+ * Observations showed the sense registers are all zero until the EC populates
+ * them after some time. Likely the EC sets all bits to it's valid state at
+ * once, but there's no prove as the firmware isn't available.
+ *
+ * Wait for any register having at least one bit set.
+ * Unlikely that all register will be zero after booting has finished.
+ *
+ * @return 1 if the EC provides valid data in sense status registers
+ */
+int h8_get_sense_ready(void)
+{
+	static const u8 regs[] = { H8_STATUS0, H8_STATUS1, H8_STATUS2,
+			H8_STATUS3};
+
+	for (size_t i = 0; i < ARRAY_SIZE(regs); i++) {
+		if (ec_read(regs[i]))
+			return 1;
+	}
+
+	return 0;
+}
+
+/**
+ * Return the state of Fn key.
+ * Only valid if h8_get_sense_ready (see above) returns true.
+ *
+ * @return 1 if the key is pressed.
+ */
+int h8_get_fn_key(void)
+{
+	return ec_read(H8_STATUS0) & H8_STATUS0_FN_KEY_DOWN;
+}