bnxt_en: reduce timeout on initial HWRM calls

Testing with DIM enabled on older kernels indicated that firmware calls
were slower than expected.  More detailed analysis indicated that the
default 25us delay was higher than necessary.  Reducing the time spend in
usleep_range() for the first several calls would reduce the overall
latency of firmware calls on newer Intel processors.

Signed-off-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -3495,15 +3495,29 @@ static int bnxt_hwrm_do_send_msg(struct bnxt *bp, void *msg, u32 msg_len,
 
 	if (!timeout)
 		timeout = DFLT_HWRM_CMD_TIMEOUT;
+	/* convert timeout to usec */
+	timeout *= 1000;
 
 	i = 0;
-	tmo_count = timeout * 40;
+	/* Short timeout for the first few iterations:
+	 * number of loops = number of loops for short timeout +
+	 * number of loops for standard timeout.
+	 */
+	tmo_count = HWRM_SHORT_TIMEOUT_COUNTER;
+	timeout = timeout - HWRM_SHORT_MIN_TIMEOUT * HWRM_SHORT_TIMEOUT_COUNTER;
+	tmo_count += DIV_ROUND_UP(timeout, HWRM_MIN_TIMEOUT);
 	resp_len = bp->hwrm_cmd_resp_addr + HWRM_RESP_LEN_OFFSET;
 	if (intr_process) {
 		/* Wait until hwrm response cmpl interrupt is processed */
 		while (bp->hwrm_intr_seq_id != HWRM_SEQ_ID_INVALID &&
 		       i++ < tmo_count) {
-			usleep_range(25, 40);
+			/* on first few passes, just barely sleep */
+			if (i < HWRM_SHORT_TIMEOUT_COUNTER)
+				usleep_range(HWRM_SHORT_MIN_TIMEOUT,
+					     HWRM_SHORT_MAX_TIMEOUT);
+			else
+				usleep_range(HWRM_MIN_TIMEOUT,
+					     HWRM_MAX_TIMEOUT);
 		}
 
 		if (bp->hwrm_intr_seq_id != HWRM_SEQ_ID_INVALID) {
@@ -3521,7 +3535,13 @@ static int bnxt_hwrm_do_send_msg(struct bnxt *bp, void *msg, u32 msg_len,
 			      HWRM_RESP_LEN_SFT;
 			if (len)
 				break;
-			usleep_range(25, 40);
+			/* on first few passes, just barely sleep */
+			if (i < DFLT_HWRM_CMD_TIMEOUT)
+				usleep_range(HWRM_SHORT_MIN_TIMEOUT,
+					     HWRM_SHORT_MAX_TIMEOUT);
+			else
+				usleep_range(HWRM_MIN_TIMEOUT,
+					     HWRM_MAX_TIMEOUT);
 		}
 
 		if (i >= tmo_count) {

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -532,6 +532,12 @@ struct rx_tpa_end_cmp_ext {
 #define BNXT_HWRM_REQ_MAX_SIZE		128
 #define BNXT_HWRM_REQS_PER_PAGE		(BNXT_PAGE_SIZE /	\
 					 BNXT_HWRM_REQ_MAX_SIZE)
+#define HWRM_SHORT_MIN_TIMEOUT		3
+#define HWRM_SHORT_MAX_TIMEOUT		10
+#define HWRM_SHORT_TIMEOUT_COUNTER	5
+
+#define HWRM_MIN_TIMEOUT		25
+#define HWRM_MAX_TIMEOUT		40
 
 #define BNXT_RX_EVENT	1
 #define BNXT_AGG_EVENT	2