Although we don't support or enable CPU PWM with LPT/SPT based systems,
it may have been enabled prior to loading the driver. Disable the CPU
PWM on LPT/SPT backlight disable to avoid warnings on LCPLL disable.
The issue has been present on BDW since BDW enabling, but was recently
introduced on HSW with
commit 437b15b8017e0d946453c10794b0c5d4591cf180
Author: Jani Nikula <jani.nikula@xxxxxxxxx>
Date: Fri Sep 4 16:55:13 2015 +0300
drm/i915: use pch backlight override on hsw too
Cc: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Reference: http://mid.gmane.org/87y4frhwsn.fsf@xxxxxxxxxxxxxxxxxxxx
Reported-by: kernel test robot <ying.huang@xxxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_panel.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index b05c6d9b3be7..a24df35e11e7 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -732,6 +732,20 @@ static void lpt_disable_backlight(struct intel_connector *connector)
intel_panel_actually_set_backlight(connector, 0);
+ /*
+ * Although we don't support or enable CPU PWM with LPT/SPT based
+ * systems, it may have been enabled prior to loading the
+ * driver. Disable to avoid warnings on LCPLL disable.
+ *
+ * This needs rework if we need to add support for CPU PWM on PCH split
+ * platforms.
+ */
+ tmp = I915_READ(BLC_PWM_CPU_CTL2);
+ if (tmp & BLM_PWM_ENABLE) {
+ DRM_DEBUG_KMS("cpu backlight was enabled, disabling\n");
+ I915_WRITE(BLC_PWM_CPU_CTL2, tmp & ~BLM_PWM_ENABLE);
+ }
+
tmp = I915_READ(BLC_PWM_PCH_CTL1);
I915_WRITE(BLC_PWM_PCH_CTL1, tmp & ~BLM_PCH_PWM_ENABLE);
}
--
2.1.4
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