[3.16.y-ckt stable] Patch "samsung-laptop: Add use_native_backlight quirk, and enable it on some models" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    samsung-laptop: Add use_native_backlight quirk, and enable it on some models

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2fe5afe766c7c871681432f60b913f72cb64a277 Mon Sep 17 00:00:00 2001
From: Hans de Goede <hdegoede at redhat.com>
Date: Fri, 9 Jan 2015 15:10:01 +0100
Subject: samsung-laptop: Add use_native_backlight quirk, and enable it on some
 models

commit 4690555e13c48fef07f2762f6b0cd6b181e326d0 upstream.

Since kernel 3.14 the backlight control has been broken on various Samsung
Atom based netbooks. This has been bisected and this problem happens since
commit b35684b8fa94 ("drm/i915: do full backlight setup at enable time")

This has been reported and discussed in detail here:
http://lists.freedesktop.org/archives/intel-gfx/2014-July/049395.html

Unfortunately no-one has been able to fix this. This only affects Samsung
Atom netbooks, and the Linux kernel and the BIOS of those laptops have never
worked well together. All affected laptops already have a quirk to avoid using
the standard acpi-video interface and instead use the samsung specific SABI
interface which samsung-laptop uses. It seems that recent fixes to the i915
driver have also broken backlight control through the SABI interface.

The intel_backlight driver OTOH works fine, and also allows for finer grained
backlight control. So add a new use_native_backlight quirk, and replace the
broken_acpi_video quirk with this quirk for affected models. This new quirk
disables acpi-video as before and also stops samsung-laptop from registering
the SABI based samsung_laptop backlight interface, leaving only the working
intel_backlight interface.

This commit enables this new quirk for 3 models which are known to be affected,
chances are that it needs to be used on other models too.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1094948 # N145P
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1115713 # N250P
Reported-by: Bertrik Sikken <bertrik at sikken.nl> # N150P
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
Signed-off-by: Darren Hart <dvhart at linux.intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/platform/x86/samsung-laptop.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c
index ff765d8e1a09..ce364a41842a 100644
--- a/drivers/platform/x86/samsung-laptop.c
+++ b/drivers/platform/x86/samsung-laptop.c
@@ -353,6 +353,7 @@ struct samsung_quirks {
 	bool broken_acpi_video;
 	bool four_kbd_backlight_levels;
 	bool enable_kbd_backlight;
+	bool use_native_backlight;
 };

 static struct samsung_quirks samsung_unknown = {};
@@ -361,6 +362,10 @@ static struct samsung_quirks samsung_broken_acpi_video = {
 	.broken_acpi_video = true,
 };

+static struct samsung_quirks samsung_use_native_backlight = {
+	.use_native_backlight = true,
+};
+
 static struct samsung_quirks samsung_np740u3e = {
 	.four_kbd_backlight_levels = true,
 	.enable_kbd_backlight = true,
@@ -1507,7 +1512,7 @@ static struct dmi_system_id __initdata samsung_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "N150P"),
 		DMI_MATCH(DMI_BOARD_NAME, "N150P"),
 		},
-	 .driver_data = &samsung_broken_acpi_video,
+	 .driver_data = &samsung_use_native_backlight,
 	},
 	{
 	 .callback = samsung_dmi_matched,
@@ -1517,7 +1522,7 @@ static struct dmi_system_id __initdata samsung_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "N145P/N250P/N260P"),
 		DMI_MATCH(DMI_BOARD_NAME, "N145P/N250P/N260P"),
 		},
-	 .driver_data = &samsung_broken_acpi_video,
+	 .driver_data = &samsung_use_native_backlight,
 	},
 	{
 	 .callback = samsung_dmi_matched,
@@ -1557,7 +1562,7 @@ static struct dmi_system_id __initdata samsung_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "N250P"),
 		DMI_MATCH(DMI_BOARD_NAME, "N250P"),
 		},
-	 .driver_data = &samsung_broken_acpi_video,
+	 .driver_data = &samsung_use_native_backlight,
 	},
 	{
 	 .callback = samsung_dmi_matched,
@@ -1616,6 +1621,15 @@ static int __init samsung_init(void)
 		pr_info("Disabling ACPI video driver\n");
 		acpi_video_unregister();
 	}
+
+	if (samsung->quirks->use_native_backlight) {
+		pr_info("Using native backlight driver\n");
+		/* Tell acpi-video to not handle the backlight */
+		acpi_video_dmi_promote_vendor();
+		acpi_video_unregister();
+		/* And also do not handle it ourselves */
+		samsung->handle_backlight = false;
+	}
 #endif

 	ret = samsung_platform_init(samsung);