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Message-ID: <20231004135317.2b460acf@kernel.org>
Date: Wed, 4 Oct 2023 13:53:17 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Radhey Shyam Pandey <radhey.shyam.pandey@....com>
Cc: <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
<robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
<conor+dt@...nel.org>, <michal.simek@....com>, <linux@...linux.org.uk>,
<f.fainelli@...il.com>, <netdev@...r.kernel.org>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <git@....com>
Subject: Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine
support
On Thu, 28 Sep 2023 01:02:31 +0530 Radhey Shyam Pandey wrote:
> +static int axienet_rx_submit_desc(struct net_device *ndev);
can the forward declaration be avoided?
> +/**
> + * axienet_dma_tx_cb - DMA engine callback for TX channel.
> + * @data: Pointer to the axienet_local structure.
> + * @result: error reporting through dmaengine_result.
> + * This function is called by dmaengine driver for TX channel to notify
> + * that the transmit is done.
> + */
> +static void axienet_dma_tx_cb(void *data, const struct dmaengine_result *result)
> +{
> + struct axienet_local *lp = data;
> + struct skbuf_dma_descriptor *skbuf_dma;
> +
> + skbuf_dma = axienet_get_tx_desc(lp, lp->tx_ring_tail++);
> + u64_stats_update_begin(&lp->tx_stat_sync);
> + u64_stats_add(&lp->tx_bytes, skbuf_dma->skb->len);
> + u64_stats_add(&lp->tx_packets, 1);
> + u64_stats_update_end(&lp->tx_stat_sync);
> + dma_unmap_sg(lp->dev, skbuf_dma->sgl, skbuf_dma->sg_len, DMA_TO_DEVICE);
> + dev_kfree_skb_any(skbuf_dma->skb);
dev_consume_skb_any(), kfree is for drops
> +/**
> + * axienet_start_xmit_dmaengine - Starts the transmission.
> + * @skb: sk_buff pointer that contains data to be Txed.
> + * @ndev: Pointer to net_device structure.
> + *
> + * Return: NETDEV_TX_OK on success or any non space errors.
> + * NETDEV_TX_BUSY when free element in TX skb ring buffer
> + * is not available.
> + *
> + * This function is invoked from xmit to initiate transmission. The
> + * function sets the skbs, register dma call back API and submit
> + * the dma transaction.
> + * Additionally if checksum offloading is supported,
> + * it populates AXI Stream Control fields with appropriate values.
> + */
> +static netdev_tx_t
> +axienet_start_xmit_dmaengine(struct sk_buff *skb, struct net_device *ndev)
> +{
> + struct dma_async_tx_descriptor *dma_tx_desc = NULL;
> + struct axienet_local *lp = netdev_priv(ndev);
> + struct skbuf_dma_descriptor *skbuf_dma;
> + u32 app_metadata[DMA_NUM_APP_WORDS] = {0};
> + u32 csum_start_off;
> + u32 csum_index_off;
> + int sg_len;
> + int ret;
> +
> + sg_len = skb_shinfo(skb)->nr_frags + 1;
> + if (!CIRC_SPACE(lp->tx_ring_head, lp->tx_ring_tail, TX_BD_NUM_MAX)) {
> + netif_stop_queue(ndev);
> + if (net_ratelimit())
> + netdev_warn(ndev, "TX ring unexpectedly full\n");
I don't see you stopping the queue when the ring gets full,
am I not looking into the right place? Otherwise this is
sort of expected to occasionally hapen
> + return NETDEV_TX_BUSY;
> + }
> +
> + skbuf_dma = axienet_get_tx_desc(lp, lp->tx_ring_head);
> + if (!skbuf_dma)
> + return NETDEV_TX_OK;
Leaks the skb?
> + lp->tx_ring_head++;
> + sg_init_table(skbuf_dma->sgl, sg_len);
> + ret = skb_to_sgvec(skb, skbuf_dma->sgl, 0, skb->len);
> + if (ret < 0)
> + return NETDEV_TX_OK;
> +
> + ret = dma_map_sg(lp->dev, skbuf_dma->sgl, sg_len, DMA_TO_DEVICE);
> + if (!ret)
> + return NETDEV_TX_OK;
> +
> + /* Fill up app fields for checksum */
> + if (skb->ip_summed == CHECKSUM_PARTIAL) {
> + if (lp->features & XAE_FEATURE_FULL_TX_CSUM) {
> + /* Tx Full Checksum Offload Enabled */
> + app_metadata[0] |= 2;
> + } else if (lp->features & XAE_FEATURE_PARTIAL_TX_CSUM) {
> + csum_start_off = skb_transport_offset(skb);
> + csum_index_off = csum_start_off + skb->csum_offset;
> + /* Tx Partial Checksum Offload Enabled */
> + app_metadata[0] |= 1;
> + app_metadata[1] = (csum_start_off << 16) | csum_index_off;
> + }
> + } else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
> + app_metadata[0] |= 2; /* Tx Full Checksum Offload Enabled */
> + }
> +
> + dma_tx_desc = lp->tx_chan->device->device_prep_slave_sg(lp->tx_chan, skbuf_dma->sgl,
Possibly store the device_prep_slave_sg pointer to a temporary variable
to make this line less painfully long?
> + skbuf_dma = axienet_get_rx_desc(lp, lp->rx_ring_head);
> + if (!skbuf_dma)
> + return -ENOMEM;
> + lp->rx_ring_head++;
> + skb = netdev_alloc_skb(ndev, lp->max_frm_size);
> + if (!skb)
> + return -ENOMEM;
> +
> + sg_init_table(skbuf_dma->sgl, 1);
> + addr = dma_map_single(lp->dev, skb->data, lp->max_frm_size, DMA_FROM_DEVICE);
> + if (unlikely(dma_mapping_error(lp->dev, addr))) {
> + netdev_err(ndev, "DMA mapping error\n");
needs rate limiting
> + ret = -ENOMEM;
> + goto rx_submit_err_free_skb;
is it legal to unmap dma error ?
> + }
> + sg_dma_address(skbuf_dma->sgl) = addr;
> + sg_dma_len(skbuf_dma->sgl) = lp->max_frm_size;
> + dma_rx_desc = dmaengine_prep_slave_sg(lp->rx_chan, skbuf_dma->sgl,
> + 1, DMA_DEV_TO_MEM,
> + DMA_PREP_INTERRUPT);
> +/**
> + * axienet_init_dmaengine - init the dmaengine code.
> + * @ndev: Pointer to net_device structure
> + *
> + * Return: 0, on success.
> + * non-zero error value on failure
> + *
> + * This is the dmaengine initialization code.
> + */
> +static int axienet_init_dmaengine(struct net_device *ndev)
> +{
> + struct axienet_local *lp = netdev_priv(ndev);
> + struct skbuf_dma_descriptor *skbuf_dma;
> + int i, ret;
> +
> + lp->tx_chan = dma_request_chan(lp->dev, "tx_chan0");
> + if (IS_ERR(lp->tx_chan)) {
> + ret = PTR_ERR(lp->tx_chan);
> + return dev_err_probe(lp->dev, ret, "No Ethernet DMA (TX) channel found\n");
Why use dev_err_probe()? This is not on the probe path. If ndo_open
fails it fails, it won't get retried later by itself, right?
> @@ -1238,7 +1540,24 @@ static int axienet_open(struct net_device *ndev)
>
> phylink_start(lp->phylink);
>
> - if (!lp->use_dmaengine) {
> + if (lp->use_dmaengine) {
> + /* Enable interrupts for Axi Ethernet core (if defined) */
> + if (lp->eth_irq > 0) {
> + ret = request_irq(lp->eth_irq, axienet_eth_irq, IRQF_SHARED,
> + ndev->name, ndev);
> + if (ret)
> + goto error_code;
> + }
> +
> + ret = axienet_init_dmaengine(ndev);
> +
pointless new line
> + if (ret < 0) {
> + if (lp->eth_irq > 0)
> + free_irq(lp->eth_irq, ndev);
can't this be on the error path?
> + goto error_code;
> + }
> +
pointless new line
> + } else {
--
pw-bot: cr
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