Message-ID: <20240613124921.GG382677@ragnatech.se>
Date: Thu, 13 Jun 2024 14:49:21 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Paul Barker <paul.barker.ct@...renesas.com>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next,v8] net: ethernet: rtsn: Add support for Renesas
 Ethernet-TSN

Hi Paul,

Thanks for your feedback.

On 2024-06-13 13:29:30 +0100, Paul Barker wrote:
> On 13/06/2024 11:41, Niklas Söderlund wrote:
> > Add initial support for Renesas Ethernet-TSN End-station device of R-Car
> > V4H. The Ethernet End-station can connect to an Ethernet network using a
> > 10 Mbps, 100 Mbps, or 1 Gbps full-duplex link via MII/GMII/RMII/RGMII.
> > Depending on the connected PHY.
> > 
> > The driver supports Rx checksum and offload and hardware timestamps.
> > 
> > While full power management and suspend/resume is not yet supported the
> > driver enables runtime PM in order to enable the module clock. While
> > explicit clock management using clk_enable() would suffice for the
> > supported SoC, the module could be reused on SoCs where the module is
> > part of a power domain.
> > 
> > Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
> > ---
> > * Changes since v7
> > - Properly handle Rx when netpoll is called with 0 budget. Previously
> >    one Rx packet would be processed in this case.
> > - Use napi_alloc_skb() instead of netdev_alloc_skb() in Rx.
> > - Use device implemented 64 bit stats instead of using stats member in
> >    struct net_device.
> > - Implement ndo_hwtstamp_{g,s}et instead of acting on SIOC{G,S}HWTSTAMP
> >    in do_ioctl().
> > - Fix incorrect error sign when using PTR_ERR().
> > - Add missing cosmetic space when creating struct of_device_id.
> > - Rename label error_alloc to error_free.
> > 
> > * Changes since v6
> > - Fix warning added when removing delays depending on phy-mode logic.
> > 
> > * Changes since v5
> > - Removed delays depending on phy-mode logic. This is only needed on
> >    some SoCs (V4H multiple boards), and currently we can't test on them.
> >    As this have been a hot topic in review drop it for now so we can
> >    support V4H single boards which we can test and lets work on the delay
> >    on-top when we can test it.
> > 
> > * Changes since v4
> > - Enable GPOUT_RDM and GPOUT_TDM delays depending on phy-mode.
> > 
> > * Changes since v3
> > - Add description to commit message why PM operations are used instead
> >    of explicit management of the clock.
> > 
> > * Changes since v2
> > - Drop extra call to ether_setup(), already called by
> >    alloc_etherdev_mqs().
> > - Remove dependency on MII.
> > - Improve error paths when requestion IRQs.
> > - Correct the interpretation of which  phy-mode to apply delays for, and
> >    mask the phy-mode passed to the PHY if MAC adds delays.
> > 
> > * Changes since v1
> > - Remove C45 read/write functions, the phy-core can do that for us.
> > - Rework the driver to register the MDIO bus at probe time instead of at
> >    ndo_open().
> > - Rework rtsn_rx() to take advantages of the improved design proposed
> >    and upstreamed for R-Car RAVB driver Rx code-path.
> > - Use napi_complete_done() instead of napi_complete().
> > - Update commit message to list that the driver supports Rx CSUM
> >    offload.
> > - Drop unneeded __iowmb() left from development as well as a stray ;.
> > - Consider all RGMII modes.
> > - Move the phy_stop() call to mirror where phy_start() is called.
> > - Forward IOCTLS from rtsn_do_ioctl() to PHY using ndo_eth_ioctl()
> > - Align variable names to match core for IOCTLS functions.
> > - Make sure DMA mask and PTP is registered before registering the ndev.
> > - Document why the RTSN driver needs to be able to apply delays
> > - Add checks for which phy-modes the MAC driver can apply delays
> > - Use snprintf() instead of sprintf()
> > 
> > * Changes since RFC
> > - Fix issues in MDIO communication.
> > - Use a dedicated OF node for the MDIO bus.
> > ---
> >   MAINTAINERS                           |    8 +
> >   drivers/net/ethernet/renesas/Kconfig  |   10 +
> >   drivers/net/ethernet/renesas/Makefile |    2 +
> >   drivers/net/ethernet/renesas/rtsn.c   | 1381 +++++++++++++++++++++++++
> >   drivers/net/ethernet/renesas/rtsn.h   |  464 +++++++++
> >   5 files changed, 1865 insertions(+)
> >   create mode 100644 drivers/net/ethernet/renesas/rtsn.c
> >   create mode 100644 drivers/net/ethernet/renesas/rtsn.h
> 
> [snip]
> 
> > +static int rtsn_rx(struct net_device *ndev, int budget)
> > +{
> > +	struct rtsn_private *priv = netdev_priv(ndev);
> > +	unsigned int ndescriptors;
> > +	unsigned int rx_packets;
> > +	unsigned int i;
> > +	bool get_ts;
> > +
> > +	get_ts = priv->ptp_priv->tstamp_rx_ctrl &
> > +		RCAR_GEN4_RXTSTAMP_TYPE_V2_L2_EVENT;
> > +
> > +	ndescriptors = priv->dirty_rx + priv->num_rx_ring - priv->cur_rx;
> > +	rx_packets = 0;
> > +	for (i = 0; i < ndescriptors; i++) {
> > +		const unsigned int entry = priv->cur_rx % priv->num_rx_ring;
> > +		struct rtsn_ext_ts_desc *desc = &priv->rx_ring[entry];
> > +		struct sk_buff *skb;
> > +		dma_addr_t dma_addr;
> > +		u16 pkt_len;
> > +
> > +		/* Stop processing descriptors if budget is consumed. */
> > +		if (rx_packets >= budget)
> > +			break;
> > +
> > +		/* Stop processing descriptors on first empty. */
> > +		if ((desc->die_dt & DT_MASK) == DT_FEMPTY)
> > +			break;
> > +
> > +		dma_rmb();
> > +		pkt_len = le16_to_cpu(desc->info_ds) & RX_DS;
> > +
> > +		skb = priv->rx_skb[entry];
> > +		priv->rx_skb[entry] = NULL;
> > +		dma_addr = le32_to_cpu(desc->dptr);
> > +		dma_unmap_single(ndev->dev.parent, dma_addr, PKT_BUF_SZ,
> > +				 DMA_FROM_DEVICE);
> > +
> > +		/* Get timestamp if enabled. */
> > +		if (get_ts) {
> > +			struct skb_shared_hwtstamps *shhwtstamps;
> > +			struct timespec64 ts;
> > +
> > +			shhwtstamps = skb_hwtstamps(skb);
> > +			memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> > +
> > +			ts.tv_sec = (u64)le32_to_cpu(desc->ts_sec);
> > +			ts.tv_nsec = le32_to_cpu(desc->ts_nsec & cpu_to_le32(0x3fffffff));
> > +
> > +			shhwtstamps->hwtstamp = timespec64_to_ktime(ts);
> > +		}
> > +
> > +		skb_put(skb, pkt_len);
> > +		skb->protocol = eth_type_trans(skb, ndev);
> > +		netif_receive_skb(skb);
> > +
> > +		/* Update statistics. */
> > +		priv->stats.rx_packets++;
> 
> I think it's better to do `priv->stats.rx_packets += rx_packets` once at
> the end of this function instead of repeatedly incrementing another
> variable on the hot path.

We could do that, but I opted for this as it makes more sens to update 
rx_packets and rx_bytes in the same location IMHO.

> 
> > +		priv->stats.rx_bytes += pkt_len;
> > +
> > +		/* Update counters. */
> > +		priv->cur_rx++;
> > +		rx_packets++;
> > +	}
> > +
> > +	/* Refill the RX ring buffers */
> > +	for (; priv->cur_rx - priv->dirty_rx > 0; priv->dirty_rx++) {
> > +		const unsigned int entry = priv->dirty_rx % priv->num_rx_ring;
> > +		struct rtsn_ext_ts_desc *desc = &priv->rx_ring[entry];
> > +		struct sk_buff *skb;
> > +		dma_addr_t dma_addr;
> > +
> > +		desc->info_ds = cpu_to_le16(PKT_BUF_SZ);
> > +
> > +		if (!priv->rx_skb[entry]) {
> > +			skb = napi_alloc_skb(&priv->napi,
> > +					     PKT_BUF_SZ + RTSN_ALIGN - 1);
> > +			if (!skb)
> > +				break;
> > +			skb_reserve(skb, NET_IP_ALIGN);
> > +			dma_addr = dma_map_single(ndev->dev.parent, skb->data,
> > +						  le16_to_cpu(desc->info_ds),
> > +						  DMA_FROM_DEVICE);
> > +			if (dma_mapping_error(ndev->dev.parent, dma_addr))
> > +				desc->info_ds = cpu_to_le16(0);
> > +			desc->dptr = cpu_to_le32(dma_addr);
> > +			skb_checksum_none_assert(skb);
> > +			priv->rx_skb[entry] = skb;
> > +		}
> > +
> > +		dma_wmb();
> > +		desc->die_dt = DT_FEMPTY | D_DIE;
> > +	}
> > +
> > +	priv->rx_ring[priv->num_rx_ring].die_dt = DT_LINK;
> > +
> > +	return rx_packets;
> > +}
> 
> [snip]
> 
> > +static netdev_tx_t rtsn_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> > +{
> > +	struct rtsn_private *priv = netdev_priv(ndev);
> > +	struct rtsn_ext_desc *desc;
> > +	int ret = NETDEV_TX_OK;
> > +	unsigned long flags;
> > +	dma_addr_t dma_addr;
> > +	int entry;
> > +
> > +	spin_lock_irqsave(&priv->lock, flags);
> > +
> > +	if (priv->cur_tx - priv->dirty_tx > priv->num_tx_ring) {
> > +		netif_stop_subqueue(ndev, 0);
> > +		ret = NETDEV_TX_BUSY;
> > +		goto out;
> > +	}
> > +
> > +	if (skb_put_padto(skb, ETH_ZLEN))
> > +		goto out;
> > +
> > +	dma_addr = dma_map_single(ndev->dev.parent, skb->data, skb->len,
> > +				  DMA_TO_DEVICE);
> > +	if (dma_mapping_error(ndev->dev.parent, dma_addr)) {
> > +		dev_kfree_skb_any(skb);
> > +		goto out;
> > +	}
> > +
> > +	entry = priv->cur_tx % priv->num_tx_ring;
> > +	priv->tx_skb[entry] = skb;
> > +	desc = &priv->tx_ring[entry];
> > +	desc->dptr = cpu_to_le32(dma_addr);
> > +	desc->info_ds = cpu_to_le16(skb->len);
> 
> Should we check against the maximum TX frame size supported by the
> hardware here?
> 
> Whatever we do here, we should also do in the ravb driver as that makes
> a similar cpu_to_le16() call to fill the DS field with no check that the
> HW actually supports transmitting a frame of the given size.

Compared to RAVB the RTSN driver do not support splitting a packet over 
multiple descriptors, so the max frame size adhering to the MTU will 
always fit using a single descriptor.

> 
> > +	desc->info1 = cpu_to_le64(skb->len);
> > +
> > +	if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
> > +		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> > +		priv->ts_tag++;
> > +		desc->info_ds |= cpu_to_le16(TXC);
> > +		desc->info = priv->ts_tag;
> > +	}
> > +
> > +	skb_tx_timestamp(skb);
> > +	dma_wmb();
> > +
> > +	desc->die_dt = DT_FSINGLE | D_DIE;
> > +	priv->cur_tx++;
> > +
> > +	/* Start xmit */
> > +	rtsn_write(priv, TRCR0, BIT(TX_CHAIN_IDX));
> > +out:
> > +	spin_unlock_irqrestore(&priv->lock, flags);
> > +	return ret;
> > +}
> 
> Thanks,
> 
> -- 
> Paul Barker






-- 
Kind Regards,
Niklas Söderlund

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