[Intel-gfx] [PATCH 5/8] drm/i915: Add the display switch logic for vgpu in i915 driver

[Jike Song]

From: Yu Zhang <yu.c.zhang at intel.com>

Display switch logic is added to notify the vgt mediator that
current vgpu have a valid surface to show. It does so by writing
the display_ready field in PV INFO page, and then will be handled
in vgt mediator. This is useful to avoid trickiness when the VM's
framebuffer is being accessed in the middle of VM modesetting,
e.g. compositing the framebuffer in the host side

Signed-off-by: Yu Zhang <yu.c.zhang at intel.com>
Signed-off-by: Jike Song <jike.song at intel.com>
Signed-off-by: Zhiyuan Lv <zhiyuan.lv at intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c      |  8 ++++++++
 drivers/gpu/drm/i915/i915_reg.h      |  7 +++++++
 drivers/gpu/drm/i915/intel_display.c | 10 ++++++++++
 3 files changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index bb4ad52..d9462e1 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1790,6 +1790,14 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	} else {
 		/* Start out suspended in ums mode. */
 		dev_priv->ums.mm_suspended = 1;
+		if (intel_vgpu_active(dev)) {
+			/*
+			 * Notify a valid surface after modesetting,
+			 * when running inside a VM.
+			 */
+			I915_WRITE(vgt_info_off(display_ready),
+				VGT_DRV_DISPLAY_READY);
+		}
 	}
 
 	i915_setup_sysfs(dev);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a70f12e..38d606c 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6673,5 +6673,12 @@ enum punit_power_well {
 #define vgt_info_off(x) \
 	(VGT_PVINFO_PAGE + (long)&((struct vgt_if *) NULL)->x)
 
+/*
+ * The information set by the guest gfx driver, through the display_ready field
+ */
+enum vgt_display_status {
+	VGT_DRV_DISPLAY_NOT_READY = 0,
+	VGT_DRV_DISPLAY_READY,	/* ready for display switch */
+};
 
 #endif /* _I915_REG_H_ */
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b78f00a..3af9259 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11642,6 +11642,16 @@ static int intel_crtc_set_config(struct drm_mode_set *set)
 			intel_modeset_check_state(set->crtc->dev);
 	}
 
+	if (intel_vgpu_active(dev)) {
+		/*
+		 * Notify a valid surface after modesetting,
+		 * when running inside a VM.
+		 */
+		struct drm_i915_private *dev_priv = dev->dev_private;
+
+		I915_WRITE(vgt_info_off(display_ready), VGT_DRV_DISPLAY_READY);
+	}
+
 	if (ret) {
 		DRM_DEBUG_KMS("failed to set mode on [CRTC:%d], err = %d\n",
 			      set->crtc->base.id, ret);
-- 
1.9.1