Change in coreboot[master]: ec/google: Detect keyboard backlight at runtime

[Patrick Georgi (Code Review)]

Patrick Georgi has uploaded this change for review. ( https://review.coreboot.org/21099

Change subject: ec/google: Detect keyboard backlight at runtime
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ec/google: Detect keyboard backlight at runtime

This enables adding the backlight driver to boards that may or may not
come with a keyboard backlight function.
It's the responsibility of the EC to report if that feature exists, but
that's not a big extra burden given that it already keeps track of
everything else related to the backlight.

BUG=b:64705535
BRANCH=none
CQ-DEPEND=CL:620595
TEST=configured the value manually and noticed the presence/absence of
/sys/firmware/platform/GOOG0002:00 on a Chrome OS Linux kernel.

Change-Id: Idc36bfaa6e69581ba19b52d37af6956f63cfdb8f
Signed-off-by: Patrick Georgi 
---
M src/ec/google/chromeec/acpi/ec.asl
M src/ec/google/chromeec/acpi/keyboard_backlight.asl
2 files changed, 11 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/99/21099/1

diff --git a/src/ec/google/chromeec/acpi/ec.asl b/src/ec/google/chromeec/acpi/ec.asl
index a532492..422abe1 100644
--- a/src/ec/google/chromeec/acpi/ec.asl
+++ b/src/ec/google/chromeec/acpi/ec.asl
@@ -54,6 +54,8 @@
    	PATC, 8,	// Programmable Auxiliary Trip Commit
    	CHGL, 8,	// Charger Current Limit
    	TBMD, 1,	// Tablet mode
+		Offset (0x0a),
+		KBLE, 1,	// Keyboard Backlight exists
    }

#if IS_ENABLED(CONFIG_EC_GOOGLE_CHROMEEC_ACPI_MEMMAP)
diff --git a/src/ec/google/chromeec/acpi/keyboard_backlight.asl b/src/ec/google/chromeec/acpi/keyboard_backlight.asl
index 75a8df3..197536a 100644
--- a/src/ec/google/chromeec/acpi/keyboard_backlight.asl
+++ b/src/ec/google/chromeec/acpi/keyboard_backlight.asl
@@ -23,6 +23,15 @@
    	Name (_HID, "GOOG0002")
    	Name (_UID, 1)

+		/* Ask EC if we even have a backlight
+		 * Return 0xf (present, enabled, show in UI, functioning) or 0
+		 */
+		Method (_STA, 0, NotSerialized)
+		{
+			Multiply (0xf, _SB.PCI0.LPCB.EC0.KBLE, Local0)
+			Return (Local0)
+		}
+
    	/* Read current backlight value */
    	Method (KBQC, 0, NotSerialized)
    	{