UBUNTU: SAUCE: drm/i915: Auto detect DPCD backlight support by default

BugLink: https://bugs.launchpad.net/bugs/1856134
Turns out we actually already have some companies, such as Lenovo,
shipping machines with AMOLED screens that don't allow controlling the
backlight through the usual PWM interface and only allow controlling it
through the standard EDP DPCD interface. One example of one of these
laptops is the X1 Extreme 2nd Generation.

Since we've got systems that need this turned on by default now to have
backlight controls working out of the box, let's start auto-detecting it
for systems by default based on what the VBT tells us. We do this by
changing the default value for the enable_dpcd_backlight module param
from 0 to -1.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
(backported from https://patchwork.freedesktop.org/patch/342165/?series=69914&rev=4)
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 296452f9efe4cbbf0ae556dcc2a26ee33af32c22..483f34ca00f510eff41a51a2553469bfdb5d6ffc 100644 (file)
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -171,7 +171,7 @@ i915_param_named_unsafe(inject_load_failure, uint, 0400,
 
 i915_param_named(enable_dpcd_backlight, int, 0600,
        "Enable support for DPCD backlight control"
-       "(-1=use per-VBT LFP backlight type setting, 0=disabled [default], 1=enabled)");
+       "(-1=use per-VBT LFP backlight type setting [default], 0=disabled, 1=enabled)");
 
 #if IS_ENABLED(CONFIG_DRM_I915_GVT)
 i915_param_named(enable_gvt, bool, 0400,

diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index d29ade3b7de6b12d0bbbd72754f457e032896505..4de41c7eb7ef490a6fb843b7835aa8e53558816b 100644 (file)
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -64,7 +64,7 @@ struct drm_printer;
        param(int, reset, 2) \
        param(unsigned int, inject_load_failure, 0) \
        param(int, fastboot, -1) \
-       param(int, enable_dpcd_backlight, 0) \
+       param(int, enable_dpcd_backlight, -1) \
        param(char *, force_probe, CONFIG_DRM_I915_FORCE_PROBE) \
        /* leave bools at the end to not create holes */ \
        param(bool, alpha_support, IS_ENABLED(CONFIG_DRM_I915_ALPHA_SUPPORT)) \