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 <[email protected]> Reviewed-by: Yoshihiro Shimoda <[email protected]> Acked-by: Sergei Shtylyov <[email protected]> Signed-off-by: David S. Miller <[email protected]>
chewitt · Sep 6, 2019 · fd8ab76 · fd8ab76
1 parent 2d957a7
commit fd8ab76
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Showing 2 changed files with 5 additions and 3 deletions.
diff --git 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
@@ -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;