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: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Jesse Barnes 2010-01-14 20:48:02 +00:00 committed by Eric Anholt
parent 21bd770b9c
commit 33814341f2
4 changed files with 8 additions and 2 deletions

View file

@ -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) { \

View file

@ -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);

View file

@ -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. ",

View file

@ -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;