FAILED: patch "[PATCH] drm/i915: Bail out of pipe config compute loop on LPT" failed to apply to 4.7-stable tree

The patch below does not apply to the 4.7-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Daniel Vetter <[email protected]>
Date: Tue, 3 May 2016 10:33:01 +0200
Subject: [PATCH] drm/i915: Bail out of pipe config compute loop on LPT

LPT is pch, so might run into the fdi bandwidth constraint (especially since it has only 2 lanes). But right now we just force pipe_bpp back to 24, resulting in a nice loop (which we bail out with a loud WARN_ON). Fix this.

Cc: Chris Wilson <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
References: https://bugs.freedesktop.org/show_bug.cgi?id=93477

index a2a31fd01d1d..3fbb6fc66451 100644
@@ -261,8 +261,14 @@ static bool intel_crt_compute_config(struct intel_encoder *encoder,
 		pipe_config->has_pch_encoder = true;
 
 	/* LPT FDI RX only supports 8bpc. */
-	if (HAS_PCH_LPT(dev))
+	if (HAS_PCH_LPT(dev)) {
+		if (pipe_config->bw_constrained && pipe_config->pipe_bpp < 24) {
+			DRM_DEBUG_KMS("LPT only supports 24bpp\n");
+			return false;
+		}
+
 		pipe_config->pipe_bpp = 24;
+	}
 
 	/* FDI must always be 2.7 GHz */
 	if (HAS_DDI(dev))