Commit 915b4179 authored Sep 19, 2016 by Shawn Lee Committed by Jani Nikula Oct 10, 2016

drm/i915/backlight: setup backlight pwm alternate increment on backlight enable

Backlight enable is supposed to do a full setup of the backlight. We
were missing the PWM alternate increment bit in the south chicken
registers on lpt+ pch. This potentially caused a PWM frequency change
when the chicken register value was lost e.g. on suspend.

v2 by Jani, rebase on the patch caching alt increment

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97486
References: https://bugs.freedesktop.org/show_bug.cgi?id=67454


Cc: Cooper Chiou <cooper.chiou@intel.com>
Cc: Wei Shun Chen <wei.shun.chang@intel.com>
Cc: Gary C Wang <gary.c.wang@intel.com>
Cc: stable@vger.kernel.org # v4.4+ 16e1203d drm/i915/backlight: setup and cache...
Cc: stable@vger.kernel.org # v4.4+
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Shawn Lee <shawn.c.lee@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/8265f5935bd31c039ddfc82819d26c2ca1ae9cba.1474281249.git.jani.nikula@intel.com


(cherry picked from commit e29aff05)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

parent 16e1203d

drivers/gpu/drm/i915/intel_panel.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -841,7 +841,7 @@ static void lpt_enable_backlight(struct intel_connector *connector)
		{
		struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
		struct intel_panel *panel = &connector->panel;
		u32 pch_ctl1, pch_ctl2;
		u32 pch_ctl1, pch_ctl2, schicken;

		pch_ctl1 = I915_READ(BLC_PWM_PCH_CTL1);
		if (pch_ctl1 & BLM_PCH_PWM_ENABLE) {
		@@ -850,6 +850,22 @@ static void lpt_enable_backlight(struct intel_connector *connector)
		I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1);
		}

		if (HAS_PCH_LPT(dev_priv)) {
		schicken = I915_READ(SOUTH_CHICKEN2);
		if (panel->backlight.alternate_pwm_increment)
		schicken \|= LPT_PWM_GRANULARITY;
		else
		schicken &= ~LPT_PWM_GRANULARITY;
		I915_WRITE(SOUTH_CHICKEN2, schicken);
		} else {
		schicken = I915_READ(SOUTH_CHICKEN1);
		if (panel->backlight.alternate_pwm_increment)
		schicken \|= SPT_PWM_GRANULARITY;
		else
		schicken &= ~SPT_PWM_GRANULARITY;
		I915_WRITE(SOUTH_CHICKEN1, schicken);
		}

		pch_ctl2 = panel->backlight.max << 16;
		I915_WRITE(BLC_PWM_PCH_CTL2, pch_ctl2);