[PATCH 2/3] net: ravb: Fix RX frame size limit

[Paul Barker]

The value written to the RFLR register includes the length of the CRC
data at the end of each Ethernet frame. So we need to increase the value
written to this register to ensure that we can receive full size frames.

While we're here we can also copy the improved comment from the Linux
kernel.

Fixes: 8ae51b6f324e ("net: ravb: Add Renesas Ethernet RAVB driver")
Signed-off-by: Paul Barker <paul.barker.ct at bp.renesas.com>
---
 drivers/net/ravb.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ravb.c b/drivers/net/ravb.c
index 6129929568a3..6bd94cf6bb1b 100644
--- a/drivers/net/ravb.c
+++ b/drivers/net/ravb.c
@@ -354,8 +354,14 @@ static int ravb_mac_init(struct ravb_priv *eth)
 	/* Disable MAC Interrupt */
 	writel(0, eth->iobase + RAVB_REG_ECSIPR);
 
-	/* Recv frame limit set register */
-	writel(RFLR_RFL_MIN, eth->iobase + RAVB_REG_RFLR);
+	/* Set receive frame length
+	 *
+	 * The length set here describes the frame from the destination address
+	 * up to and including the CRC data. However only the frame data,
+	 * excluding the CRC, are transferred to memory. To allow for the
+	 * largest frames add the CRC length to the maximum Rx descriptor size.
+	 */
+	writel(RFLR_RFL_MIN + ETH_FCS_LEN, eth->iobase + RAVB_REG_RFLR);
 
 	return 0;
 }
-- 
2.43.0