intel_th: Skip subdevices if their MMIO is missing

If a subdevice requires an MMIO region that wasn't in the resources passed
down from the glue layer, don't instantiate it, but don't error out. This
means that that particular subdevice doesn't exist for this instance of
Intel TH, which is a perfectly normal situation. This applies, for example,
to the "rtit" source device.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/intel_th/core.c

@@ -607,6 +607,9 @@ intel_th_subdevice_alloc(struct intel_th *th,
 		 */
 		if (!res[r].end && res[r].flags == IORESOURCE_MEM) {
 			bar = res[r].start;
+			err = -ENODEV;
+			if (bar >= th->num_resources)
+				goto fail_put_device;
 			res[r].start = 0;
 			res[r].end = resource_size(&devres[bar]) - 1;
 		}
@@ -749,8 +752,13 @@ static int intel_th_populate(struct intel_th *th)
 
 		thdev = intel_th_subdevice_alloc(th, subdev);
 		/* note: caller should free subdevices from th::thdev[] */
-		if (IS_ERR(thdev))
+		if (IS_ERR(thdev)) {
+			/* ENODEV for individual subdevices is allowed */
+			if (PTR_ERR(thdev) == -ENODEV)
+				continue;
+
 			return PTR_ERR(thdev);
+		}
 
 		th->thdev[th->num_thdevs++] = thdev;
 	}
@@ -813,9 +821,6 @@ intel_th_alloc(struct device *dev, struct intel_th_drvdata *drvdata,
 	struct intel_th *th;
 	int err, r;
 
-	if (ndevres < TH_MMIO_END)
-		return ERR_PTR(-EINVAL);
-
 	th = kzalloc(sizeof(*th), GFP_KERNEL);
 	if (!th)
 		return ERR_PTR(-ENOMEM);