netdev - [PATCH net-next v2 2/4] ravb: remove undocumented counter processing

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Date:   Thu,  5 Sep 2019 17:10:57 +0200
From:   Simon Horman <horms+renesas@...ge.net.au>
To:     David Miller <davem@...emloft.net>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     Magnus Damm <magnus.damm@...il.com>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Simon Horman <horms+renesas@...ge.net.au>
Subject: [PATCH net-next v2 2/4] ravb: remove undocumented counter processing

This patch removes the use of the undocumented counter registers
CDCR, LCCR, CERCR, CEECR.

Offsets used for undocumented registers are considered reserved and
should not be written to. After some internal investigation with Renesas
it remains unclear why this driver accesses these fields but regardless of
what the historical reasons are the current code is considered incorrect.

Based on work by Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>

Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
---
v2
* New patch broken out of larger patch
---
 drivers/net/ethernet/renesas/ravb.h      | 4 ----
 drivers/net/ethernet/renesas/ravb_main.c | 9 ---------
 2 files changed, 13 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 2596a95a4300..70eeceb7f8ae 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -194,15 +194,11 @@ enum ravb_reg {
 	MAHR	= 0x05c0,
 	MALR	= 0x05c8,
 	TROCR	= 0x0700,	/* Undocumented? */
-	CDCR	= 0x0708,	/* Undocumented? */
-	LCCR	= 0x0710,	/* Undocumented? */
 	CEFCR	= 0x0740,
 	FRECR	= 0x0748,
 	TSFRCR	= 0x0750,
 	TLFRCR	= 0x0758,
 	RFCR	= 0x0760,
-	CERCR	= 0x0768,	/* Undocumented? */
-	CEECR	= 0x0770,	/* Undocumented? */
 	MAFCR	= 0x0778,
 };
 
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 6cacd5e893ac..4d1f274cded0 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1629,15 +1629,6 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
 
 	nstats->tx_dropped += ravb_read(ndev, TROCR);
 	ravb_write(ndev, 0, TROCR);	/* (write clear) */
-	nstats->collisions += ravb_read(ndev, CDCR);
-	ravb_write(ndev, 0, CDCR);	/* (write clear) */
-	nstats->tx_carrier_errors += ravb_read(ndev, LCCR);
-	ravb_write(ndev, 0, LCCR);	/* (write clear) */
-
-	nstats->tx_carrier_errors += ravb_read(ndev, CERCR);
-	ravb_write(ndev, 0, CERCR);	/* (write clear) */
-	nstats->tx_carrier_errors += ravb_read(ndev, CEECR);
-	ravb_write(ndev, 0, CEECR);	/* (write clear) */
 
 	nstats->rx_packets = stats0->rx_packets + stats1->rx_packets;
 	nstats->tx_packets = stats0->tx_packets + stats1->tx_packets;
-- 
2.11.0