drivers:hv: Separate out frame buffer logic when picking MMIO range

Simplify the logic that picks MMIO ranges by pulling out the
logic related to trying to lay frame buffer claim on top of where
the firmware placed the frame buffer.
Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/vmbus_drv.c

@@ -1162,56 +1162,47 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 			bool fb_overlap_ok)
 {
 	struct resource *iter, *shadow;
-	resource_size_t range_min, range_max, start, local_min, local_max;
+	resource_size_t range_min, range_max, start;
 	const char *dev_n = dev_name(&device_obj->device);
-	u32 fb_end = screen_info.lfb_base + (screen_info.lfb_size << 1);
-	int i, retval;
+	int retval;
 
 	retval = -ENXIO;
 	down(&hyperv_mmio_lock);
 
+	/*
+	 * If overlaps with frame buffers are allowed, then first attempt to
+	 * make the allocation from within the reserved region.  Because it
+	 * is already reserved, no shadow allocation is necessary.
+	 */
+	if (fb_overlap_ok && fb_mmio && !(min > fb_mmio->end) &&
+	    !(max < fb_mmio->start)) {
+
+		range_min = fb_mmio->start;
+		range_max = fb_mmio->end;
+		start = (range_min + align - 1) & ~(align - 1);
+		for (; start + size - 1 <= range_max; start += align) {
+			*new = request_mem_region_exclusive(start, size, dev_n);
+			if (*new) {
+				retval = 0;
+				goto exit;
+			}
+		}
+	}
+
 	for (iter = hyperv_mmio; iter; iter = iter->sibling) {
 		if ((iter->start >= max) || (iter->end <= min))
 			continue;
 
 		range_min = iter->start;
 		range_max = iter->end;
-
-		/* If this range overlaps the frame buffer, split it into
-		   two tries. */
-		for (i = 0; i < 2; i++) {
-			local_min = range_min;
-			local_max = range_max;
-			if (fb_overlap_ok || (range_min >= fb_end) ||
-			    (range_max <= screen_info.lfb_base)) {
-				i++;
-			} else {
-				if ((range_min <= screen_info.lfb_base) &&
-				    (range_max >= screen_info.lfb_base)) {
-					/*
-					 * The frame buffer is in this window,
-					 * so trim this into the part that
-					 * preceeds the frame buffer.
-					 */
-					local_max = screen_info.lfb_base - 1;
-					range_min = fb_end;
-				} else {
-					range_min = fb_end;
-					continue;
-				}
-			}
-
-			start = (local_min + align - 1) & ~(align - 1);
-			for (; start + size - 1 <= local_max; start += align) {
-				shadow = __request_region(iter, start,
-							  size,
-							  NULL,
+		start = (range_min + align - 1) & ~(align - 1);
+		for (; start + size - 1 <= range_max; start += align) {
+			shadow = __request_region(iter, start, size, NULL,
 						  IORESOURCE_BUSY);
 			if (!shadow)
 				continue;
 
-				*new = request_mem_region_exclusive(start, size,
-								    dev_n);
+			*new = request_mem_region_exclusive(start, size, dev_n);
 			if (*new) {
 				shadow->name = (char *)*new;
 				retval = 0;
@@ -1221,7 +1212,6 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 			__release_region(iter, start, size);
 		}
 	}
-	}
 
 exit:
 	up(&hyperv_mmio_lock);