drm/i915: Disable gpu relocations

Media userspace was the last userspace to still use them, and they
converted now too:

intel/media-driver@144020c

This means no reason anymore to make relocations faster than they've
been for the first 9 years of gem. This code was added in

commit 7dd4f67
Author: Chris Wilson <[email protected]>
Date:   Fri Jun 16 15:05:24 2017 +0100

    drm/i915: Async GPU relocation processing

Furthermore there's pretty strong indications it's buggy, since the
code to use it by default as the only option had to be reverted:

commit ad5d95e
Author: Dave Airlie <[email protected]>
Date:   Tue Sep 8 15:41:17 2020 +1000

    Revert "drm/i915/gem: Async GPU relocations only"

This code just disables gpu relocations, leaving the garbage
collection for later patches and more importantly, much less confusing
diff. Also given how much headaches this code has caused in the past,
letting this soak for a bit seems justified.

Acked-by: Dave Airlie <[email protected]>
Reviewed-by: Maarten Lankhorst <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Cc: Jon Bloomfield <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: "Thomas Hellström" <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: Lionel Landwerlin <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Jason Ekstrand <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: danvet

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -1577,7 +1577,7 @@ static int __reloc_entry_gpu(struct i915_execbuffer *eb,
 	return true;
 }
 
-static int reloc_entry_gpu(struct i915_execbuffer *eb,
+static int __maybe_unused reloc_entry_gpu(struct i915_execbuffer *eb,
 			    struct i915_vma *vma,
 			    u64 offset,
 			    u64 target_addr)
@@ -1599,32 +1599,25 @@ relocate_entry(struct i915_vma *vma,
 {
 	u64 target_addr = relocation_target(reloc, target);
 	u64 offset = reloc->offset;
-	int reloc_gpu = reloc_entry_gpu(eb, vma, offset, target_addr);
-
-	if (reloc_gpu < 0)
-		return reloc_gpu;
-
-	if (!reloc_gpu) {
-		bool wide = eb->reloc_cache.use_64bit_reloc;
-		void *vaddr;
+	bool wide = eb->reloc_cache.use_64bit_reloc;
+	void *vaddr;
 
 repeat:
-		vaddr = reloc_vaddr(vma->obj, eb,
-				    offset >> PAGE_SHIFT);
-		if (IS_ERR(vaddr))
-			return PTR_ERR(vaddr);
-
-		GEM_BUG_ON(!IS_ALIGNED(offset, sizeof(u32)));
-		clflush_write32(vaddr + offset_in_page(offset),
-				lower_32_bits(target_addr),
-				eb->reloc_cache.vaddr);
-
-		if (wide) {
-			offset += sizeof(u32);
-			target_addr >>= 32;
-			wide = false;
-			goto repeat;
-		}
+	vaddr = reloc_vaddr(vma->obj, eb,
+			    offset >> PAGE_SHIFT);
+	if (IS_ERR(vaddr))
+		return PTR_ERR(vaddr);
+
+	GEM_BUG_ON(!IS_ALIGNED(offset, sizeof(u32)));
+	clflush_write32(vaddr + offset_in_page(offset),
+			lower_32_bits(target_addr),
+			eb->reloc_cache.vaddr);
+
+	if (wide) {
+		offset += sizeof(u32);
+		target_addr >>= 32;
+		wide = false;
+		goto repeat;
 	}
 
 	return target->node.start | UPDATE;