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Commit 33814341 authored by Jesse Barnes's avatar Jesse Barnes Committed by Eric Anholt
Browse files

drm/i915: disable LVDS downclock by default 



Many platform support this feature, and it can provide significant
power savings when the reduced refresh rate is low.  However, on some
platforms a secondary (reduced) timing is provided but not actually
supported by the hardware.  This results in undesirable flicker at
runtime.

So disable the feature by default, but allow users to opt-in to the
reduced clock behavior with a new module parameter, lvds_downclock,
that can be set to 1 to enable the feature.

Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: default avatarEric Anholt <eric@anholt.net>
parent 21bd770b

drivers/gpu/drm/i915/i915_drv.c

+3 −0
Original line number Diff line number Diff line
@@ -45,6 +45,9 @@ module_param_named(fbpercrtc, i915_fbpercrtc, int, 0400); 
unsigned int i915_powersave = 1;

module_param_named(powersave, i915_powersave, int, 0400);



unsigned int i915_lvds_downclock = 0;

module_param_named(lvds_downclock, i915_lvds_downclock, int, 0400);



static struct drm_driver driver;



#define INTEL_VGA_DEVICE(id, info) {		\

drivers/gpu/drm/i915/i915_drv.h

+1 −0
Original line number Diff line number Diff line
@@ -722,6 +722,7 @@ extern struct drm_ioctl_desc i915_ioctls[]; 
extern int i915_max_ioctl;

extern unsigned int i915_fbpercrtc;

extern unsigned int i915_powersave;

extern unsigned int i915_lvds_downclock;



extern void i915_save_display(struct drm_device *dev);

extern void i915_restore_display(struct drm_device *dev);

drivers/gpu/drm/i915/intel_bios.c

+2 −1
Original line number Diff line number Diff line
@@ -197,7 +197,8 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv, 
		memset(temp_mode, 0, sizeof(*temp_mode));

	}

	kfree(temp_mode);

	if (temp_downclock < panel_fixed_mode->clock) {

	if (temp_downclock < panel_fixed_mode->clock &&

	    i915_lvds_downclock) {

		dev_priv->lvds_downclock_avail = 1;

		dev_priv->lvds_downclock = temp_downclock;

		DRM_DEBUG_KMS("LVDS downclock is found in VBT. ",

drivers/gpu/drm/i915/intel_lvds.c

+2 −1
Original line number Diff line number Diff line
@@ -926,7 +926,8 @@ static void intel_find_lvds_downclock(struct drm_device *dev, 
		}

	}

	mutex_unlock(&dev->mode_config.mutex);

	if (temp_downclock < panel_fixed_mode->clock) {

	if (temp_downclock < panel_fixed_mode->clock &&

	    i915_lvds_downclock) {

		/* We found the downclock for LVDS. */

		dev_priv->lvds_downclock_avail = 1;

		dev_priv->lvds_downclock = temp_downclock;