nfp: fix invalid area detection

Core should detect when someone is trying to request an access
window which is too large for a given type of access.  Otherwise
the requester will be put on a wait queue for ever without any
error message.

Add const qualifiers to clarify that we are only looking at read-
-only members in relevant functions.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfpcore/nfp6000_pcie.c

@@ -217,7 +217,7 @@ static resource_size_t nfp_bar_resource_start(struct nfp_bar *bar)
 #define TARGET_WIDTH_64    8
 
 static int
-compute_bar(struct nfp6000_pcie *nfp, struct nfp_bar *bar,
+compute_bar(const struct nfp6000_pcie *nfp, const struct nfp_bar *bar,
 	    u32 *bar_config, u64 *bar_base,
 	    int tgt, int act, int tok, u64 offset, size_t size, int width)
 {
@@ -410,35 +410,36 @@ find_matching_bar(struct nfp6000_pcie *nfp,
 
 /* Return EAGAIN if no resource is available */
 static int
-find_unused_bar_noblock(struct nfp6000_pcie *nfp,
+find_unused_bar_noblock(const struct nfp6000_pcie *nfp,
 			int tgt, int act, int tok,
 			u64 offset, size_t size, int width)
 {
-	int n, invalid = 0;
+	int n, busy = 0;
 
 	for (n = 0; n < nfp->bars; n++) {
-		struct nfp_bar *bar = &nfp->bar[n];
+		const struct nfp_bar *bar = &nfp->bar[n];
 		int err;
 
-		if (bar->bitsize == 0) {
-			invalid++;
-			continue;
-		}
-
-		if (atomic_read(&bar->refcnt) != 0)
+		if (!bar->bitsize)
 			continue;
 
 		/* Just check to see if we can make it fit... */
 		err = compute_bar(nfp, bar, NULL, NULL,
 				  tgt, act, tok, offset, size, width);
+		if (err)
+			continue;
 
-		if (err < 0)
-			invalid++;
-		else
+		if (!atomic_read(&bar->refcnt))
 			return n;
+
+		busy++;
 	}
 
-	return (n == invalid) ? -EINVAL : -EAGAIN;
+	if (WARN(!busy, "No suitable BAR found for request tgt:0x%x act:0x%x tok:0x%x off:0x%llx size:%zd width:%d\n",
+		 tgt, act, tok, offset, size, width))
+		return -EINVAL;
+
+	return -EAGAIN;
 }
 
 static int