[PATCH net-next v2 5/6] bnxt_en: Use a larger RSS indirection table on P5_PLUS chips

[Michael Chan <michael.chan@broadcom.com>]

The driver currently uses a chip supported RSS indirection table size
just big enough to cover the number of RX rings.  Each table with 64
entries requires one HW RSS context.  The HW supported table sizes are
64, 128, 256, and 512 entries.  Using the smallest table size can cause
unbalanced RSS packet distributions.  For example, if the number of
rings is 48, the table size using existing logic will be 64.  32 rings
will have a weight of 1 and 16 rings will have a weight of 2 when
set to default even distribution.  This represents a 100% difference in
weights between some of the rings.

Newer FW has increased the RSS indirection table resource.  When the
increased resource is detected, use the largest RSS indirection table
size (512 entries) supported by the chip.  Using the same example
above, the weights of the 48 rings will be either 10 or 11 when set to
default even distribution.  The weight difference is only 10%.

If there are thousands of VFs, there is a possiblity that we may not
be able to allocate this larger RSS indirection table from the FW, so
we add a check to fall back to the legacy scheme.

Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 12 ++++++++++++
 drivers/net/ethernet/broadcom/bnxt/bnxt.h |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 9ab9ebd57367..9efdc382ebd7 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -6558,6 +6558,9 @@ int bnxt_get_nr_rss_ctxs(struct bnxt *bp, int rx_rings)
 	if (bp->flags & BNXT_FLAG_CHIP_P5_PLUS) {
 		if (!rx_rings)
 			return 0;
+		if (bp->rss_cap & BNXT_RSS_CAP_LARGE_RSS_CTX)
+			return BNXT_RSS_TABLE_MAX_TBL_P5;
+
 		return bnxt_calc_nr_ring_pages(rx_rings - 1,
 					       BNXT_RSS_TABLE_ENTRIES_P5);
 	}
@@ -8068,6 +8071,11 @@ static int __bnxt_reserve_rings(struct bnxt *bp)
 	bp->rx_nr_rings = rx_rings;
 	bp->cp_nr_rings = hwr.cp;
 
+	/* Fall back if we cannot reserve enough HW RSS contexts */
+	if ((bp->rss_cap & BNXT_RSS_CAP_LARGE_RSS_CTX) &&
+	    hwr.rss_ctx < bnxt_get_total_rss_ctxs(bp, &hwr))
+		bp->rss_cap &= ~BNXT_RSS_CAP_LARGE_RSS_CTX;
+
 	if (!bnxt_rings_ok(bp, &hwr))
 		return -ENOMEM;
 
@@ -9558,6 +9566,10 @@ int bnxt_hwrm_func_resc_qcaps(struct bnxt *bp, bool all)
 	hw_resc->min_stat_ctxs = le16_to_cpu(resp->min_stat_ctx);
 	hw_resc->max_stat_ctxs = le16_to_cpu(resp->max_stat_ctx);
 
+	if (hw_resc->max_rsscos_ctxs >=
+	    hw_resc->max_vnics * BNXT_LARGE_RSS_TO_VNIC_RATIO)
+		bp->rss_cap |= BNXT_RSS_CAP_LARGE_RSS_CTX;
+
 	if (bp->flags & BNXT_FLAG_CHIP_P5_PLUS) {
 		u16 max_msix = le16_to_cpu(resp->max_msix);
 
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 2a2d172fa6ed..476c5684a1eb 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -1369,6 +1369,8 @@ struct bnxt_hw_resc {
 	u32	max_rx_wm_flows;
 };
 
+#define BNXT_LARGE_RSS_TO_VNIC_RATIO	7
+
 #if defined(CONFIG_BNXT_SRIOV)
 struct bnxt_vf_info {
 	u16	fw_fid;
@@ -2412,6 +2414,7 @@ struct bnxt {
 #define BNXT_RSS_CAP_ESP_V6_RSS_CAP		BIT(7)
 #define BNXT_RSS_CAP_MULTI_RSS_CTX		BIT(8)
 #define BNXT_RSS_CAP_IPV6_FLOW_LABEL_RSS_CAP	BIT(9)
+#define BNXT_RSS_CAP_LARGE_RSS_CTX		BIT(10)
 
 	u8			rss_hash_key[HW_HASH_KEY_SIZE];
 	u8			rss_hash_key_valid:1;
-- 
2.51.0