netdev - [net-next 2/3] ravb: Remove undocumented processing

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Date:   Mon,  2 Sep 2019 10:06:02 +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,
        Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>,
        Simon Horman <horms+renesas@...ge.net.au>
Subject: [net-next 2/3] ravb: Remove undocumented processing

From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>

This patch removes the use of the undocumented registers
CDCR, LCCR, CERCR, CEECR and the undocumented BOC bit of the CCC register.

Current documentation for EtherAVB (ravb) describes the offset of
what the driver uses as the BOC bit as reserved and that only a value of
0 should be written. Furthermore, the offsets used for the undocumented
registers are also considered reserved nd 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.

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
---
 drivers/net/ethernet/renesas/ravb.h      |  5 -----
 drivers/net/ethernet/renesas/ravb_main.c | 15 ---------------
 2 files changed, 20 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 2596a95a4300..bdb051f04b0c 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,
 };
 
@@ -220,7 +216,6 @@ enum CCC_BIT {
 	CCC_CSEL_HPB	= 0x00010000,
 	CCC_CSEL_ETH_TX	= 0x00020000,
 	CCC_CSEL_GMII_REF = 0x00030000,
-	CCC_BOC		= 0x00100000,	/* Undocumented? */
 	CCC_LBME	= 0x01000000,
 };
 
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 6cacd5e893ac..b538cc6fdbb7 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -447,12 +447,6 @@ static int ravb_dmac_init(struct net_device *ndev)
 	ravb_ring_format(ndev, RAVB_BE);
 	ravb_ring_format(ndev, RAVB_NC);
 
-#if defined(__LITTLE_ENDIAN)
-	ravb_modify(ndev, CCC, CCC_BOC, 0);
-#else
-	ravb_modify(ndev, CCC, CCC_BOC, CCC_BOC);
-#endif
-
 	/* Set AVB RX */
 	ravb_write(ndev,
 		   RCR_EFFS | RCR_ENCF | RCR_ETS0 | RCR_ESF | 0x18000000, RCR);
@@ -1629,15 +1623,6 @@ 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