[Intel-gfx] [PATCH v2 2/3] drm/i915: noop forcewake get/put when vgpu activated

[Weinan Li]

Host maintian the hardware's forcewake state, guest don't need and also
can't control it. Although vgpu_read/write bypass forcewake_get/put in MMIO
read/write, but still have separate path called by
"intel_uncore_forcewake_get/put" and
"intel_uncore_forcewake_get/put__locked". Unnecessary MMIO access in guest
waste much CPU cost. Since we full virtualize the MMIO, just noop the
forcewake get/put.

Signed-off-by: Weinan Li <weinan.z.li at intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index abe0888..9fad4de 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -133,6 +133,13 @@
 }
 
 static void
+vgpu_fw_domains_nop(struct drm_i915_private *dev_priv,
+		    enum forcewake_domains fw_domains)
+{
+	/* Guest driver doesn't need to takes care forcewake. */
+}
+
+static void
 fw_domains_posting_read(struct drm_i915_private *dev_priv)
 {
 	struct intel_uncore_forcewake_domain *d;
@@ -1374,6 +1381,12 @@ static void intel_uncore_fw_domains_init(struct drm_i915_private *dev_priv)
 		fw_domain_init(dev_priv, FW_DOMAIN_ID_RENDER,
 			       FORCEWAKE, FORCEWAKE_ACK);
 	}
+	if (intel_vgpu_active(dev_priv)) {
+		dev_priv->uncore.funcs.force_wake_get =
+			vgpu_fw_domains_nop;
+		dev_priv->uncore.funcs.force_wake_put =
+			vgpu_fw_domains_nop;
+	}
 
 	/* All future platforms are expected to require complex power gating */
 	WARN_ON(dev_priv->uncore.fw_domains == 0);
-- 
1.9.1