From: Alex Deucher <alexander.deucher@amd.com>
Date: Wed, 19 Nov 2014 18:12:54 +0000 (-0500)
Subject: drm/radeon: disable native backlight control on pre-r6xx asics (v2)
X-Git-Tag: v3.17.5~15
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7b48f096b4996401fd707e989a9c6c7447404531;p=thirdparty%2Fkernel%2Fstable.git

drm/radeon: disable native backlight control on pre-r6xx asics (v2)

commit b7bc596ebbe0cddc97d76ef9309f64471bbf13eb upstream.

Just use the acpi interface.  That's what windows uses on this
generation and it's the only thing that seems to work reliably
on these generation parts.

You can still force the native backlight interface by setting
radeon.backlight=1

Bug:
https://bugzilla.kernel.org/show_bug.cgi?id=88501

v2: merge into above if/else block

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 15edf23b465c2..1ca64b615fc05 100644
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -179,6 +179,9 @@ static void radeon_encoder_add_backlight(struct radeon_encoder *radeon_encoder,
 		    (rdev->pdev->subsystem_vendor == 0x1734) &&
 		    (rdev->pdev->subsystem_device == 0x1107))
 			use_bl = false;
+		/* disable native backlight control on older asics */
+		else if (rdev->family < CHIP_R600)
+			use_bl = false;
 		else
 			use_bl = true;
 	}