RE: [RFC/PATCH 16/18] ravb: Add Packet receive function for Gigabit Ethernet

Hi Sergey,

Thanks for the feedback.

Subject: Re: [RFC/PATCH 16/18] ravb: Add Packet receive function for
Gigabit Ethernet

On 9/23/21 5:08 PM, Biju Das wrote:

quoted

This patch series adds RX(packet receive) function for Gigabit
Ethernet found on RZ/G2L SoC.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
---
 drivers/net/ethernet/renesas/ravb.h      |   1 +
 drivers/net/ethernet/renesas/ravb_main.c | 157
++++++++++++++++++++++-
 2 files changed, 156 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h

b/drivers/net/ethernet/renesas/ravb.h
index b0e067a6a8ee..85260f89e1cd 100644

--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h

@@ -1092,6 +1092,7 @@ struct ravb_private {

 	int duplex;
 	struct ravb_rx_desc *rgeth_rx_ring[NUM_RX_QUEUE];
+	struct sk_buff *rxtop_skb;

   I'd prefer for this one declared earler in the *struct*, as well. And
why not e.g 'rx_1st_skb'?

OK Will use 'rx_1st_skb' in the next RFC version.

quoted

 	const struct ravb_hw_info *info;
 	struct reset_control *rstc;

diff --git a/drivers/net/ethernet/renesas/ravb_main.c

b/drivers/net/ethernet/renesas/ravb_main.c
index a08da7a37b92..867e180e6655 100644

--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c

@@ -705,6 +705,23 @@ static void ravb_get_tx_tstamp(struct net_device

*ndev)

quoted

 	}
 }

+static void ravb_rx_csum_rgeth(struct sk_buff *skb) {
+	u8 *hw_csum;
+
+	/* The hardware checksum is contained in sizeof(__sum16) (2) bytes
+	 * appended to packet data
+	 */
+	if (unlikely(skb->len < sizeof(__sum16)))
+		return;
+	hw_csum = skb_tail_pointer(skb) - sizeof(__sum16);
+
+	if (*hw_csum == 0)
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
+	else
+		skb->ip_summed = CHECKSUM_NONE;

   Mhm, what's the point of this whole function then? Why it can't be a
copy of the R-Car analog?

This function should come after CSR initialization. Next RFC I will taken care of this.
*hwcsum == 0 means, there is no error in checksum. So it should be OK.

[...]

quoted

@@ -720,11 +737,147 @@ static void ravb_rx_csum(struct sk_buff *skb)

[...]

quoted

 /* Packet receive function for Gigabit Ethernet */  static bool
ravb_rgeth_rx(struct net_device *ndev, int *quota, int q)  {
-	/* Place holder */
-	return true;
+	struct ravb_private *priv = netdev_priv(ndev);
+	int entry = priv->cur_rx[q] % priv->num_rx_ring[q];
+	int boguscnt = priv->dirty_rx[q] + priv->num_rx_ring[q] - priv-
cur_rx[q];
+	struct net_device_stats *stats = &priv->stats[q];

   [q] should be dropped, as we've agreed...

nc_queue feature bit will take care of this. So the q will be always RVAB_BE.

quoted

+	struct ravb_rx_desc *desc;
+	struct sk_buff *skb;
+	dma_addr_t dma_addr;
+	u8  desc_status;
+	u8  die_dt;
+	u16 pkt_len;
+	int limit;
+
+	boguscnt = min(boguscnt, *quota);
+	limit = boguscnt;
+	desc = &priv->rgeth_rx_ring[q][entry];
+	while (desc->die_dt != DT_FEMPTY) {
+		/* Descriptor type must be checked before all other reads */
+		dma_rmb();
+		desc_status = desc->msc;
+		pkt_len = le16_to_cpu(desc->ds_cc) & RX_DS;
+
+		if (--boguscnt < 0)
+			break;
+
+		/* We use 0-byte descriptors to mark the DMA mapping errors */
+		if (!pkt_len)
+			continue;
+
+		if (desc_status & MSC_MC)
+			stats->multicast++;
+
+		if (desc_status & (MSC_CRC | MSC_RFE | MSC_RTSF | MSC_RTLF |

MSC_CEEF)) {

quoted

+			stats->rx_errors++;
+			if (desc_status & MSC_CRC)
+				stats->rx_crc_errors++;
+			if (desc_status & MSC_RFE)
+				stats->rx_frame_errors++;
+			if (desc_status & (MSC_RTLF | MSC_RTSF))
+				stats->rx_length_errors++;
+			if (desc_status & MSC_CEEF)
+				stats->rx_missed_errors++;
+		} else {
+			die_dt = desc->die_dt & 0xF0;
+			switch (die_dt) {
+			case DT_FSINGLE:
+				skb = ravb_get_skb_rgeth(ndev, q, entry, desc);
+				skb_put(skb, pkt_len);
+				skb->protocol = eth_type_trans(skb, ndev);
+				if (ndev->features & NETIF_F_RXCSUM)
+					ravb_rx_csum_rgeth(skb);
+				napi_gro_receive(&priv->napi[q], skb);
+				stats->rx_packets++;
+				stats->rx_bytes += pkt_len;
+				break;
+			case DT_FSTART:
+				priv->rxtop_skb = ravb_get_skb_rgeth(ndev, q,

entry, desc);

   But don't you need to  copy the data in this case?

It is not required, here. 

quoted

+				skb_put(priv->rxtop_skb, pkt_len);
+				break;
+			case DT_FMID:
+				skb = ravb_get_skb_rgeth(ndev, q, entry, desc);
+				skb_copy_to_linear_data_offset(priv->rxtop_skb,
+							       priv->rxtop_skb->len,
+							       skb->data,
+							       pkt_len);
+				skb_put(priv->rxtop_skb, pkt_len);
+				dev_kfree_skb(skb);
+				break;
+			case DT_FEND:
+				skb = ravb_get_skb_rgeth(ndev, q, entry, desc);
+				skb_copy_to_linear_data_offset(priv->rxtop_skb,
+							       priv->rxtop_skb->len,
+							       skb->data,
+							       pkt_len);
+				skb_put(priv->rxtop_skb, pkt_len);
+				dev_kfree_skb(skb);
+				priv->rxtop_skb->protocol =
+					eth_type_trans(priv->rxtop_skb, ndev);
+				if (ndev->features & NETIF_F_RXCSUM)
+					ravb_rx_csum_rgeth(skb);
+				napi_gro_receive(&priv->napi[q],
+						 priv->rxtop_skb);
+				stats->rx_packets++;
+				stats->rx_bytes += priv->rxtop_skb->len;
+				break;
+			}
+		}
+
+		entry = (++priv->cur_rx[q]) % priv->num_rx_ring[q];
+		desc = &priv->rgeth_rx_ring[q][entry];
+	}
+
+	/* Refill the RX ring buffers. */
+	for (; priv->cur_rx[q] - priv->dirty_rx[q] > 0; priv->dirty_rx[q]++)

{

quoted

+		entry = priv->dirty_rx[q] % priv->num_rx_ring[q];
+		desc = &priv->rgeth_rx_ring[q][entry];
+		desc->ds_cc = cpu_to_le16(RGETH_RX_DESC_DATA_SIZE);
+
+		if (!priv->rx_skb[q][entry]) {
+			skb = netdev_alloc_skb(ndev,
+					       RGETH_RX_BUFF_MAX + RAVB_ALIGN - 1);

   ALIGN(RGETH_RX_BUFF_MAX, RAVB_ALIGN)?

It is taken care in next RFC.

Regards,
Biju

[...]

MBR, Sergey