netdev - [PATCH net-next v2 4/4] ravb: TROCR register is only present on R-Car Gen3

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Message-Id: <20190905151059.26794-5-horms+renesas@verge.net.au>
Date:   Thu,  5 Sep 2019 17:10:59 +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 4/4] ravb: TROCR register is only present on R-Car Gen3

Only use the TROCR register on R-Car Gen3 as it is not present on other
SoCs.

Offsets used for the 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 on R-Car Gen2 but
regardless of what the historical reasons are the current code is
considered incorrect.

Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Acked-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
---
v2
* Accumulated tags
* Updated changelog
---
 drivers/net/ethernet/renesas/ravb.h      | 2 +-
 drivers/net/ethernet/renesas/ravb_main.c | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index bdb051f04b0c..a9c89d5d8898 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -193,7 +193,7 @@ enum ravb_reg {
 	GECMR	= 0x05b0,
 	MAHR	= 0x05c0,
 	MALR	= 0x05c8,
-	TROCR	= 0x0700,	/* Undocumented? */
+	TROCR	= 0x0700,	/* R-Car Gen3 only */
 	CEFCR	= 0x0740,
 	FRECR	= 0x0748,
 	TSFRCR	= 0x0750,
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index b538cc6fdbb7..de9aa8c47f1c 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1621,8 +1621,10 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
 	stats0 = &priv->stats[RAVB_BE];
 	stats1 = &priv->stats[RAVB_NC];
 
-	nstats->tx_dropped += ravb_read(ndev, TROCR);
-	ravb_write(ndev, 0, TROCR);	/* (write clear) */
+	if (priv->chip_id == RCAR_GEN3) {
+		nstats->tx_dropped += ravb_read(ndev, TROCR);
+		ravb_write(ndev, 0, TROCR);	/* (write clear) */
+	}
 
 	nstats->rx_packets = stats0->rx_packets + stats1->rx_packets;
 	nstats->tx_packets = stats0->tx_packets + stats1->tx_packets;
-- 
2.11.0