Turn on backlight when LVDS panel is powered up

In some configurations, the LVDS may be off at startup along with the
backlight.  So when turning the LVDS on for the first time, we may also need to
set the backlight to a non-zero value.  So try to use the saved value if
possible, but if it's zero, make the backlight full brightness when turning on
the LVDS.

Note that this is slightly sub-optimal for configurations where zero is a valid backlight brightness.

Fixes fdo bz #13958.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/i830_lvds.c b/src/i830_lvds.c
index 50ecb606..ef8fa4a9 100644
--- a/src/i830_lvds.c
+++ b/src/i830_lvds.c
@@ -372,6 +372,17 @@ i830SetLVDSPanelPower(xf86OutputPtr output, Bool on)
     CARD32		    pp_status;
 
     if (on) {
+	/*
+	 * If we're going from off->on we may need to turn on the backlight.
+	 * We should use the saved value whenever possible, but on some
+	 * machines 0 is a valid backlight value (due to an external backlight
+	 * controller for example), so on them, when turning LVDS back on,
+	 * they'll always re-maximize the brightness.
+	 */
+	if (!(INREG(PP_CONTROL) & POWER_TARGET_ON) &&
+	    dev_priv->backlight_duty_cycle == 0)
+	    dev_priv->backlight_duty_cycle = dev_priv->backlight_max;
+
 	OUTREG(PP_CONTROL, INREG(PP_CONTROL) | POWER_TARGET_ON);
 	do {
 	    pp_status = INREG(PP_STATUS);