drm/i915: Make most pre-skl primary plane registers unlocked

Drop the locks around most primary plane register writes.
The lock isn't needed since each plane's register are neatly
contained on their own cachelines.

The one exception we have to make is DSPADDR/DSPSURF which is
(ab)used to also trigger FBC nukes on pre-snb (since the
hardware doesn't seem to have any dedicated mechanism to
trigger nukes). So we need to keep the lock around it to
protect against the rmw performed by the fbc code.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220210062403.18690-5-ville.syrjala@linux.intel.comReviewed-by: NStanislav Lisovskiy <stanislav.lisovskiy@intel.com>

drivers/gpu/drm/i915/display/i9xx_plane.c

@@ -418,9 +418,6 @@ static void i9xx_plane_update_noarm(struct intel_plane *plane,
 {
 	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
 	enum i9xx_plane_id i9xx_plane = plane->i9xx_plane;
-	unsigned long irqflags;
-
-	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 
 	intel_de_write_fw(dev_priv, DSPSTRIDE(i9xx_plane),
 			  plane_state->view.color_plane[0].mapping_stride);
@@ -441,8 +438,6 @@ static void i9xx_plane_update_noarm(struct intel_plane *plane,
 		intel_de_write_fw(dev_priv, DSPSIZE(i9xx_plane),
 				  DISP_HEIGHT(crtc_h - 1) | DISP_WIDTH(crtc_w - 1));
 	}
-
-	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
 }
 
 static void i9xx_plane_update_arm(struct intel_plane *plane,
@@ -465,8 +460,6 @@ static void i9xx_plane_update_arm(struct intel_plane *plane,
 	else
 		dspaddr_offset = linear_offset;
 
-	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
-
 	if (IS_CHERRYVIEW(dev_priv) && i9xx_plane == PLANE_B) {
 		int crtc_x = plane_state->uapi.dst.x1;
 		int crtc_y = plane_state->uapi.dst.y1;
@@ -496,13 +489,15 @@ static void i9xx_plane_update_arm(struct intel_plane *plane,
 	 * the control register just before the surface register.
 	 */
 	intel_de_write_fw(dev_priv, DSPCNTR(i9xx_plane), dspcntr);
+
+	/* lock to protect against rmw in fbc nuke */
+	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 	if (DISPLAY_VER(dev_priv) >= 4)
 		intel_de_write_fw(dev_priv, DSPSURF(i9xx_plane),
 				  intel_plane_ggtt_offset(plane_state) + dspaddr_offset);
 	else
 		intel_de_write_fw(dev_priv, DSPADDR(i9xx_plane),
 				  intel_plane_ggtt_offset(plane_state) + dspaddr_offset);
-
 	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
 }
 
@@ -540,14 +535,14 @@ static void i9xx_plane_disable_arm(struct intel_plane *plane,
 	 */
 	dspcntr = i9xx_plane_ctl_crtc(crtc_state);
 
-	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
-
 	intel_de_write_fw(dev_priv, DSPCNTR(i9xx_plane), dspcntr);
+
+	/* lock to protect against rmw in fbc nuke */
+	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 	if (DISPLAY_VER(dev_priv) >= 4)
 		intel_de_write_fw(dev_priv, DSPSURF(i9xx_plane), 0);
 	else
 		intel_de_write_fw(dev_priv, DSPADDR(i9xx_plane), 0);
-
 	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
 }
 
@@ -566,8 +561,10 @@ g4x_primary_async_flip(struct intel_plane *plane,
 	if (async_flip)
 		dspcntr |= DISP_ASYNC_FLIP;
 
-	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 	intel_de_write_fw(dev_priv, DSPCNTR(i9xx_plane), dspcntr);
+
+	/* lock to protect against rmw in fbc nuke */
+	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 	intel_de_write_fw(dev_priv, DSPSURF(i9xx_plane),
 			  intel_plane_ggtt_offset(plane_state) + dspaddr_offset);
 	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
@@ -582,12 +579,9 @@ vlv_primary_async_flip(struct intel_plane *plane,
 	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
 	u32 dspaddr_offset = plane_state->view.color_plane[0].offset;
 	enum i9xx_plane_id i9xx_plane = plane->i9xx_plane;
-	unsigned long irqflags;
 
-	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 	intel_de_write_fw(dev_priv, DSPADDR_VLV(i9xx_plane),
 			  intel_plane_ggtt_offset(plane_state) + dspaddr_offset);
-	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
 }
 
 static void