Change in coreboot[master]: drivers/intel/gma: Fix OpRegion Mailbox3 backlight change

[Nico Huber (Code Review)]

Nico Huber has uploaded this change for review. ( https://review.coreboot.org/28300

Change subject: drivers/intel/gma: Fix OpRegion Mailbox3 backlight change
......................................................................

drivers/intel/gma: Fix OpRegion Mailbox3 backlight change

The ACPI interface always uses a percentage for the brightness value,
BCLP, OTOH, is defined to take a value from 0 to 255. We also always
update BCLP, no matter if the driver is ready yet to process the re-
quest. This way it will hold the current value when the driver ini-
tializes.

Change-Id: I4b091d744f95da39abe542966f0a8589a187573b
Signed-off-by: Nico Huber 
---
M src/drivers/intel/gma/acpi/configure_brightness_levels.asl
1 file changed, 6 insertions(+), 1 deletion(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/00/28300/1

diff --git a/src/drivers/intel/gma/acpi/configure_brightness_levels.asl b/src/drivers/intel/gma/acpi/configure_brightness_levels.asl
index 8625f04..72e5466 100644
--- a/src/drivers/intel/gma/acpi/configure_brightness_levels.asl
+++ b/src/drivers/intel/gma/acpi/configure_brightness_levels.asl
@@ -2,6 +2,7 @@
  * This file is part of the coreboot project.
  *
  * Copyright (C) 2015 Nico Huber 
+ * Copyright (C) 2018 Nico Huber 
  * Copyright (C) 2018 Patrick Rudolph
  *
  * This program is free software; you can redistribute it and/or modify
@@ -64,12 +65,16 @@
    		{
    			Return (Ones)
    		}
+
+			/* Always keep BCLP up to date, even if driver is not ready */
+			Store (Divide (Multiply (Arg0, 255), 100), Local0)
+			Store (Or (Local0, 0x80000000), BCLP)
+
    		If (LEqual(ARDY, Zero))
    		{
    			Return (Ones)
    		}

-			Store (Or (Arg0, 0x80000000), BCLP)
    		/* Request back-light change */
    		Store (0x2, ASLC)
    		/* Trigger IRQ */