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drm/i915: do not setup backlight if not available according to VBT

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Some machines use an external EC for controlling the backlight. Info
about this is present in the VBT. Do not setup native backlight control
if no PWM backlight is available or supported according to VBT. The
acpi_backlight interface appears to work for the EC control.

In most cases there has been no harm done, but it looks like there are
machines out there that have both an EC and our PWM line connected to
the same wire. This, obviously, does not end well.

This should fix the regression caused by
commit bc0bb9fd1c
Author: Jani Nikula <[email protected]>
Date:   Thu Nov 14 12:14:29 2013 +0200

    drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE

AFAICT the quirk removed by the above commit effectively resulted in
i915 not driving the backlight PWM output, thus not messing things up.

Additionally this should fix the regression caused by
commit fbc9fe1b4f
Author: Aaron Lu <[email protected]>
Date:   Fri Oct 11 21:27:45 2013 +0800

    ACPI / video: Do not register backlight if win8 and native interface exists

which left some machines without a functioning backlight interface.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76276
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=47941
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=62281
CC: Aaron Lu <[email protected]>
CC: Eric Griffith <[email protected]>
CC: Kent Baxley <[email protected]>
Tested-by: Kamal Mostafa <[email protected]>
Tested-by: Martin <[email protected]>
Tested-by: [email protected]
Reviewed-by: Ville Syrjälä <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
This commit is contained in:
Jani Nikula 2014-04-09 11:31:37 +03:00
commit c675949ec5
1 changed files with 5 additions and 0 deletions
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5
drivers/gpu/drm/i915/intel_panel.c
View file

@ -1065,6 +1065,11 @@ int intel_panel_setup_backlight(struct drm_connector *connector)
unsigned long flags;
int ret;
if (!dev_priv->vbt.backlight.present) {
DRM_DEBUG_KMS("native backlight control not available per VBT\n");
return 0;
}
/* set level and max in panel struct */
spin_lock_irqsave(&dev_priv->backlight_lock, flags);
ret = dev_priv->display.setup_backlight(intel_connector);