powerpc/vas: Validate window credits

NX-842, the only user of VAS, sets the window credits to default values
but VAS should check the credits against the possible max values.

The VAS_WCREDS_MIN is not needed and can be dropped.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/vas-window.c

@@ -738,6 +738,9 @@ static bool rx_win_args_valid(enum vas_cop_type cop,
 	if (attr->rx_fifo_size > VAS_RX_FIFO_SIZE_MAX)
 		return false;
 
+	if (attr->wcreds_max > VAS_RX_WCREDS_MAX)
+		return false;
+
 	if (attr->nx_win) {
 		/* cannot be fault or user window if it is nx */
 		if (attr->fault_win || attr->user_win)
@@ -927,6 +930,9 @@ static bool tx_win_args_valid(enum vas_cop_type cop,
 	if (cop > VAS_COP_TYPE_MAX)
 		return false;
 
+	if (attr->wcreds_max > VAS_TX_WCREDS_MAX)
+		return false;
+
 	if (attr->user_win &&
 			(cop != VAS_COP_TYPE_FTW || attr->rsvd_txbuf_count))
 		return false;

arch/powerpc/platforms/powernv/vas.h

@@ -106,8 +106,8 @@
  *
  * TODO: Needs tuning for per-process credits
  */
-#define VAS_WCREDS_MIN			16
-#define VAS_WCREDS_MAX			((64 << 10) - 1)
+#define VAS_RX_WCREDS_MAX		((64 << 10) - 1)
+#define VAS_TX_WCREDS_MAX		((4 << 10) - 1)
 #define VAS_WCREDS_DEFAULT		(1 << 10)
 
 /*