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From:   MD Danish Anwar <danishanwar@ti.com>
To:     MD Danish Anwar <danishanwar@ti.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>
CC:     <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <srk@ti.com>, Vignesh Raghavendra <vigneshr@ti.com>,
        <r-gunasekaran@ti.com>, Roger Quadros <rogerq@kernel.org>
Subject: [PATCH] net: ti: icssg-prueth: Fix tx_total_bytes count
Date:   Wed, 11 Oct 2023 12:07:00 +0530
Message-ID: <20231011063700.1824093-1-danishanwar@ti.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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Precedence: bulk

ICSSG HW stats on TX side considers 8 preamble bytes as data bytes. Due
to this the tx_total_bytes of one interface doesn't match the
rx_total_bytes of other interface when two ICSSG interfaces are
connected with each other. There is no public errata available yet.

As a workaround to fix this, decrease tx_total_bytes by 8 bytes for every
tx frame.

Fixes: c1e10d5dc7a1 ("net: ti: icssg-prueth: Add ICSSG Stats")
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
---
 drivers/net/ethernet/ti/icssg/icssg_stats.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_stats.c b/drivers/net/ethernet/ti/icssg/icssg_stats.c
index bb0b33927e3b..dc12edcbac02 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_stats.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_stats.c
@@ -18,6 +18,7 @@ void emac_update_hardware_stats(struct prueth_emac *emac)
 	struct prueth *prueth = emac->prueth;
 	int slice = prueth_emac_slice(emac);
 	u32 base = stats_base[slice];
+	u32 tx_pkt_cnt = 0;
 	u32 val;
 	int i;
 
@@ -29,7 +30,12 @@ void emac_update_hardware_stats(struct prueth_emac *emac)
 			     base + icssg_all_stats[i].offset,
 			     val);
 
+		if (!strncmp(icssg_ethtool_stats[i].name, "tx_good_frames", ETH_GSTRING_LEN))
+			tx_pkt_cnt = val;
+
 		emac->stats[i] += val;
+		if (!strncmp(icssg_ethtool_stats[i].name, "tx_total_bytes", ETH_GSTRING_LEN))
+			emac->stats[i] -= tx_pkt_cnt * 8;
 	}
 }
 
-- 
2.34.1