drm/i915: properly enable the blc controller on the right pipe

On gen4+ we have a bitfield to specify from which pipe the backlight
controller should take it's clock. For PCH split platforms we've
already set these up, but only at initialization time. And without
taking into account the 3rd pipe added with ivb.

For gen4, we've completely ignored these. Although we do restrict lvds
to the 2nd pipe, so this is only a problem on machines where we boot
up with the lvds on the first pipe.

So restructure the code to enable the backlight on the right pipe at
modeset time.

v2: For odd reasons panel_enable_backlight gets called twice in a
modeset, so we can't WARN_ON in there if the backlight controller is
switched on already.

v3: backlight enable can also be called through dpms on, so the check
in there is legit. Update the comment to reflect that.

Tested-By: Kamal Mostafa <kamal@canonical.com>
Bugzilla: https://bugs.launchpad.net/bugs/954661
Cc: Carsten Emde <C.Emde@osadl.org>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 37 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 7180cc828f9..58c7ee7238b 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -287,9 +287,18 @@ void intel_panel_disable_backlight(struct drm_device *dev)
 
 	dev_priv->backlight_enabled = false;
 	intel_panel_actually_set_backlight(dev, 0);
+
+	if (INTEL_INFO(dev)->gen >= 4) {
+		uint32_t reg;
+
+		reg = HAS_PCH_SPLIT(dev) ? BLC_PWM_CPU_CTL2 : BLC_PWM_CTL2;
+
+		I915_WRITE(reg, I915_READ(reg) & ~BLM_PWM_ENABLE);
+	}
 }
 
-void intel_panel_enable_backlight(struct drm_device *dev)
+void intel_panel_enable_backlight(struct drm_device *dev,
+				  enum pipe pipe)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
@@ -298,6 +307,33 @@ void intel_panel_enable_backlight(struct drm_device *dev)
 
 	dev_priv->backlight_enabled = true;
 	intel_panel_actually_set_backlight(dev, dev_priv->backlight_level);
+
+	if (INTEL_INFO(dev)->gen >= 4) {
+		uint32_t reg, tmp;
+
+		reg = HAS_PCH_SPLIT(dev) ? BLC_PWM_CPU_CTL2 : BLC_PWM_CTL2;
+
+
+		tmp = I915_READ(reg);
+
+		/* Note that this can also get called through dpms changes. And
+		 * we don't track the backlight dpms state, hence check whether
+		 * we have to do anything first. */
+		if (tmp & BLM_PWM_ENABLE)
+			return;
+
+		if (dev_priv->num_pipe == 3)
+			tmp &= ~BLM_PIPE_SELECT_IVB;
+		else
+			tmp &= ~BLM_PIPE_SELECT;
+
+		tmp |= BLM_PIPE(pipe);
+		tmp &= ~BLM_PWM_ENABLE;
+
+		I915_WRITE(reg, tmp);
+		POSTING_READ(reg);
+		I915_WRITE(reg, tmp | BLM_PWM_ENABLE);
+	}
 }
 
 static void intel_panel_init_backlight(struct drm_device *dev)