drm/i915: Also clear the punit's PDATA sideband register

As the previous punit i/o may have failed, the contents of the PDATA are
undefined. Always clear it to 0 prior to sending the command.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170125134808.6152-2-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

diff --git a/drivers/gpu/drm/i915/intel_sideband.c b/drivers/gpu/drm/i915/intel_sideband.c
index d3d49a0..9f782b5 100644 (file)
--- a/drivers/gpu/drm/i915/intel_sideband.c
+++ b/drivers/gpu/drm/i915/intel_sideband.c
@@ -60,8 +60,7 @@ static int vlv_sideband_rw(struct drm_i915_private *dev_priv, u32 devfn,
        }
 
        I915_WRITE(VLV_IOSF_ADDR, addr);
-       if (!is_read)
-               I915_WRITE(VLV_IOSF_DATA, *val);
+       I915_WRITE(VLV_IOSF_DATA, is_read ? 0 : *val);
        I915_WRITE(VLV_IOSF_DOORBELL_REQ, cmd);
 
        if (intel_wait_for_register(dev_priv,
@@ -74,7 +73,6 @@ static int vlv_sideband_rw(struct drm_i915_private *dev_priv, u32 devfn,
 
        if (is_read)
                *val = I915_READ(VLV_IOSF_DATA);
-       I915_WRITE(VLV_IOSF_DATA, 0);
 
        return 0;
 }