drm/i915/lvds: Connect the PWM to the LVDS pipe

... and do not just assume to always use pipe B.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index 23247b235e68..d07055c4d84f 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -1012,10 +1012,18 @@ bool intel_lvds_init(struct drm_device *dev)
 out:
         if (HAS_PCH_SPLIT(dev)) {
                 u32 pwm;
-                /* make sure PWM is enabled */
+
+                pipe = (I915_READ(PCH_LVDS) & LVDS_PIPEB_SELECT) ? 1 : 0;
+
+                /* make sure PWM is enabled and locked to the LVDS pipe */
                 pwm = I915_READ(BLC_PWM_CPU_CTL2);
-                pwm |= (PWM_ENABLE | PWM_PIPE_B);
-                I915_WRITE(BLC_PWM_CPU_CTL2, pwm);
+                if (pipe == 0 && (pwm & PWM_PIPE_B))
+                        I915_WRITE(BLC_PWM_CPU_CTL2, pwm & ~PWM_ENABLE);
+                if (pipe)
+                        pwm |= PWM_PIPE_B;
+                else
+                        pwm &= ~PWM_PIPE_B;
+                I915_WRITE(BLC_PWM_CPU_CTL2, pwm | PWM_ENABLE);
 
                 pwm = I915_READ(BLC_PWM_PCH_CTL1);
                 pwm |= PWM_PCH_ENABLE;