xhci: Check size rather then number of streams when allocating stream ctxs

Before this a device needing ie 32 stream ctxs would end up with an entry from
the small_streams_pool which has 256 bytes entries, where as 32 stream ctxs
need 512 bytes. Things actually keep running for a surprisingly long time
before crashing because of this.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-mem.c

@@ -520,12 +520,12 @@ static void xhci_free_stream_ctx(struct xhci_hcd *xhci,
 		struct xhci_stream_ctx *stream_ctx, dma_addr_t dma)
 {
 	struct device *dev = xhci_to_hcd(xhci)->self.controller;
+	size_t size = sizeof(struct xhci_stream_ctx) * num_stream_ctxs;
 
-	if (num_stream_ctxs > MEDIUM_STREAM_ARRAY_SIZE)
-		dma_free_coherent(dev,
-				sizeof(struct xhci_stream_ctx)*num_stream_ctxs,
+	if (size > MEDIUM_STREAM_ARRAY_SIZE)
+		dma_free_coherent(dev, size,
 				stream_ctx, dma);
-	else if (num_stream_ctxs <= SMALL_STREAM_ARRAY_SIZE)
+	else if (size <= SMALL_STREAM_ARRAY_SIZE)
 		return dma_pool_free(xhci->small_streams_pool,
 				stream_ctx, dma);
 	else
@@ -548,12 +548,12 @@ static struct xhci_stream_ctx *xhci_alloc_stream_ctx(struct xhci_hcd *xhci,
 		gfp_t mem_flags)
 {
 	struct device *dev = xhci_to_hcd(xhci)->self.controller;
+	size_t size = sizeof(struct xhci_stream_ctx) * num_stream_ctxs;
 
-	if (num_stream_ctxs > MEDIUM_STREAM_ARRAY_SIZE)
-		return dma_alloc_coherent(dev,
-				sizeof(struct xhci_stream_ctx)*num_stream_ctxs,
+	if (size > MEDIUM_STREAM_ARRAY_SIZE)
+		return dma_alloc_coherent(dev, size,
 				dma, mem_flags);
-	else if (num_stream_ctxs <= SMALL_STREAM_ARRAY_SIZE)
+	else if (size <= SMALL_STREAM_ARRAY_SIZE)
 		return dma_pool_alloc(xhci->small_streams_pool,
 				mem_flags, dma);
 	else