crypto/NX: Set receive window credits to max number of CRBs in RxFIFO

System gets checkstop if RxFIFO overruns with more requests than the
maximum possible number of CRBs in FIFO at the same time. The max number
of requests per window is controlled by window credits. So find max
CRBs from FIFO size and set it to receive window credits.

Fixes: b0d6c9ba ("crypto/nx: Add P9 NX support for 842 compression engine")
CC: stable@vger.kernel.org # v4.14+
Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/nx/nx-842-powernv.c

@@ -36,8 +36,6 @@ MODULE_ALIAS_CRYPTO("842-nx");
 #define WORKMEM_ALIGN	(CRB_ALIGN)
 #define CSB_WAIT_MAX	(5000) /* ms */
 #define VAS_RETRIES	(10)
-/* # of requests allowed per RxFIFO at a time. 0 for unlimited */
-#define MAX_CREDITS_PER_RXFIFO	(1024)
 
 struct nx842_workmem {
 	/* Below fields must be properly aligned */
@@ -821,7 +819,11 @@ static int __init vas_cfg_coproc_info(struct device_node *dn, int chip_id,
 	rxattr.lnotify_lpid = lpid;
 	rxattr.lnotify_pid = pid;
 	rxattr.lnotify_tid = tid;
-	rxattr.wcreds_max = MAX_CREDITS_PER_RXFIFO;
+	/*
+	 * Maximum RX window credits can not be more than #CRBs in
+	 * RxFIFO. Otherwise, can get checkstop if RxFIFO overruns.
+	 */
+	rxattr.wcreds_max = fifo_size / CRB_SIZE;
 
 	/*
 	 * Open a VAS receice window which is used to configure RxFIFO