FAILED: patch "[PATCH] drm/i915: Fix dbuf slice config lookup" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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 698bef8ff5d2edea5d1c9d6e5adf1bfed1e8a106 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>
Date: Mon, 7 Feb 2022 15:26:59 +0200
Subject: [PATCH] drm/i915: Fix dbuf slice config lookup
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Apparently I totally fumbled the loop condition when I removed the ARRAY_SIZE() stuff from the dbuf slice config lookup. Comparing the loop index with the active_pipes bitmask is utter nonsense, what we want to do is check to see if the mask is zero or not.

Note that the code actually ended up working correctly despite the fumble, up until commit eef173954432 ("drm/i915: Allow !join_mbus cases for adlp+ dbuf configuration") when things broke for real.

index 3edba7fd0c49..da6ce24a42b2 100644
@@ -4870,7 +4870,7 @@ static u8 compute_dbuf_slices(enum pipe pipe, u8 active_pipes, bool join_mbus,
 {
 	int i;
 
-	for (i = 0; i < dbuf_slices[i].active_pipes; i++) {
+	for (i = 0; dbuf_slices[i].active_pipes != 0; i++) {
 		if (dbuf_slices[i].active_pipes == active_pipes &&
 		    dbuf_slices[i].join_mbus == join_mbus)
 			return dbuf_slices[i].dbuf_mask[pipe];