The operations when setting dpms on should be in the order opposite
of what's done when setting dpms off.
This is because of potentially conflicting effects:
~ drmModeConnectoSetProperty() enables/disables the backlight driver.
Some backlight drivers such as intel_backlight set the backlight to 0
when disabled and to max when enabled.
~ intel_output_dpms_backlight() saves the backlight value when turning
DPMS off and restores it when turning DPMS on.
Here's the current order of operations:
xset dpms force off (backlight is nonzero)
drmModeConnectoSetProperty(DPMSModeOff)
kernel: disable backlight, backlight=0
intel_output_dpms_backlight(DPMSModeOff)
save backlight value (0) <-- it has been set to 0 by kernel
set backlight to 0
xset dpms force on
drmModeConnectoSetProperty(DPMSModeOn)
kernel: enable backlight, backlight=max
intel_output_dpms_backlight(DPMSModeOn)
set backlight to saved value (0)
The correct way to do this would be to reverse the operations during
xset dpms force off:
intel_output_dpms_backlight(DPMSModeOff)
save backlight value (nonzero)
set backlight to 0
drmModeConnectoSetProperty(DPMSModeOff)
kernel: enable backlight, backlight=0
This restores the saved nonzero backlight value during the force on.
Signed-off-by: Simon Que <sque at chromium.org>
---
src/intel_display.c | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/intel_display.c b/src/intel_display.c
index 2183f4d..2a989d1 100644
--- a/src/intel_display.c
+++ b/src/intel_display.c
@@ -944,13 +944,19 @@ intel_output_dpms(xf86OutputPtr output, int dpms)
continue;
if (!strcmp(props->name, "DPMS")) {
+ /* Make sure to reverse the order between on and off. */
+ if (dpms == DPMSModeOff)
+ intel_output_dpms_backlight(output,
+ intel_output->dpms_mode,
+ dpms);
drmModeConnectorSetProperty(mode->fd,
intel_output->output_id,
props->prop_id,
dpms);
- intel_output_dpms_backlight(output,
- intel_output->dpms_mode,
- dpms);
+ if (dpms != DPMSModeOff)
+ intel_output_dpms_backlight(output,
+ intel_output->dpms_mode,
+ dpms);
intel_output->dpms_mode = dpms;
drmModeFreeProperty(props);
return;
--
1.7.3.1
