Re: [PATCH v2 2/2] net: ti: icssg-prueth: Add ICSSG ethernet driver

[Md Danish Anwar <a0501179@ti.com>]

Hi Paolo,

I am Danish, new addition to TI team. Puranjay left TI, I'll be posting
upstream patches for Programmable Real-time Unit and Industrial Communication
Subsystem Gigabit (PRU_ICSSG).

On 31/05/22 16:53, Paolo Abeni wrote:
> On Tue, 2022-05-31 at 15:21 +0530, Puranjay Mohan wrote:
> [...]
>> +static int emac_tx_complete_packets(struct prueth_emac *emac, int chn,
>> +				    int budget)
>> +{
>> +	struct net_device *ndev = emac->ndev;
>> +	struct cppi5_host_desc_t *desc_tx;
>> +	struct netdev_queue *netif_txq;
>> +	struct prueth_tx_chn *tx_chn;
>> +	unsigned int total_bytes = 0;
>> +	struct sk_buff *skb;
>> +	dma_addr_t desc_dma;
>> +	int res, num_tx = 0;
>> +	void **swdata;
>> +
>> +	tx_chn = &emac->tx_chns[chn];
>> +
>> +	while (budget--) {
>> +		res = k3_udma_glue_pop_tx_chn(tx_chn->tx_chn, &desc_dma);
>> +		if (res == -ENODATA)
>> +			break;
>> +
>> +		/* teardown completion */
>> +		if (cppi5_desc_is_tdcm(desc_dma)) {
>> +			if (atomic_dec_and_test(&emac->tdown_cnt))
>> +				complete(&emac->tdown_complete);
>> +			break;
>> +		}
>> +
>> +		desc_tx = k3_cppi_desc_pool_dma2virt(tx_chn->desc_pool,
>> +						     desc_dma);
>> +		swdata = cppi5_hdesc_get_swdata(desc_tx);
>> +
>> +		skb = *(swdata);
>> +		prueth_xmit_free(tx_chn, desc_tx);
>> +
>> +		ndev = skb->dev;
>> +		ndev->stats.tx_packets++;
>> +		ndev->stats.tx_bytes += skb->len;
>> +		total_bytes += skb->len;
>> +		napi_consume_skb(skb, budget);
> 
> The above is uncorrect. In this loop's last iteration 'budget' will  be
> 0 and napi_consume_skb will wrongly assume the caller is not in NAPI
> context. 
> 

Yes, in the current approach, in last iteration budget will be zero. To avoid
this, we can change the looping condition. Instead of while(budget--), it could
be while(budget) and budget will be decreamented at the end of the loop.
This way in the last iteration budget value will not be zero.

The while loop will look like this.

while (budget) {
    res = k3_udma_glue_pop_tx_chn(tx_chn->tx_chn, &desc_dma);
	if (res == -ENODATA)
		break;

	/* teardown completion */
	if (cppi5_desc_is_tdcm(desc_dma)) {
		if (atomic_dec_and_test(&emac->tdown_cnt))
			complete(&emac->tdown_complete);
		break;
	}

	desc_tx = k3_cppi_desc_pool_dma2virt(tx_chn->desc_pool,
					     desc_dma);
	swdata = cppi5_hdesc_get_swdata(desc_tx);

	skb = *(swdata);
	prueth_xmit_free(tx_chn, desc_tx);

	ndev = skb->dev;
	ndev->stats.tx_packets++;
	ndev->stats.tx_bytes += skb->len;
	total_bytes += skb->len;
	napi_consume_skb(skb, budget);
	num_tx++;
        budget--;
}

Please let me know if this seems ok.


>> +static int prueth_dma_rx_push(struct prueth_emac *emac,
>> +			      struct sk_buff *skb,
>> +			      struct prueth_rx_chn *rx_chn)
>> +{
>> +	struct cppi5_host_desc_t *desc_rx;
>> +	struct net_device *ndev = emac->ndev;
>> +	dma_addr_t desc_dma;
>> +	dma_addr_t buf_dma;
>> +	u32 pkt_len = skb_tailroom(skb);
>> +	void **swdata;
>> +
>> +	desc_rx = k3_cppi_desc_pool_alloc(rx_chn->desc_pool);
>> +	if (!desc_rx) {
>> +		netdev_err(ndev, "rx push: failed to allocate descriptor\n");
>> +		return -ENOMEM;
>> +	}
>> +	desc_dma = k3_cppi_desc_pool_virt2dma(rx_chn->desc_pool, desc_rx);
>> +
>> +	buf_dma = dma_map_single(rx_chn->dma_dev, skb->data, pkt_len, DMA_FROM_DEVICE);
>> +	if (unlikely(dma_mapping_error(rx_chn->dma_dev, buf_dma))) {
>> +		k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>> +		netdev_err(ndev, "rx push: failed to map rx pkt buffer\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	cppi5_hdesc_init(desc_rx, CPPI5_INFO0_HDESC_EPIB_PRESENT,
>> +			 PRUETH_NAV_PS_DATA_SIZE);
>> +	k3_udma_glue_rx_dma_to_cppi5_addr(rx_chn->rx_chn, &buf_dma);
>> +	cppi5_hdesc_attach_buf(desc_rx, buf_dma, skb_tailroom(skb), buf_dma, skb_tailroom(skb));
>> +
>> +	swdata = cppi5_hdesc_get_swdata(desc_rx);
>> +	*swdata = skb;
>> +
>> +	return k3_udma_glue_push_rx_chn(rx_chn->rx_chn, 0,
>> +					desc_rx, desc_dma);
>> +}
>> +
>> +static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
>> +{
>> +	struct prueth_rx_chn *rx_chn = &emac->rx_chns;
>> +	struct net_device *ndev = emac->ndev;
>> +	struct cppi5_host_desc_t *desc_rx;
>> +	dma_addr_t desc_dma, buf_dma;
>> +	u32 buf_dma_len, pkt_len, port_id = 0;
>> +	int ret;
>> +	void **swdata;
>> +	struct sk_buff *skb, *new_skb;
>> +
>> +	ret = k3_udma_glue_pop_rx_chn(rx_chn->rx_chn, flow_id, &desc_dma);
>> +	if (ret) {
>> +		if (ret != -ENODATA)
>> +			netdev_err(ndev, "rx pop: failed: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	if (cppi5_desc_is_tdcm(desc_dma)) /* Teardown ? */
>> +		return 0;
>> +
>> +	desc_rx = k3_cppi_desc_pool_dma2virt(rx_chn->desc_pool, desc_dma);
>> +
>> +	swdata = cppi5_hdesc_get_swdata(desc_rx);
>> +	skb = *swdata;
>> +
>> +	cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
>> +	k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
>> +	pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
>> +	/* firmware adds 4 CRC bytes, strip them */
>> +	pkt_len -= 4;
>> +	cppi5_desc_get_tags_ids(&desc_rx->hdr, &port_id, NULL);
>> +
>> +	dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len, DMA_FROM_DEVICE);
>> +	k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>> +
>> +	skb->dev = ndev;
>> +	if (!netif_running(skb->dev)) {
>> +		dev_kfree_skb_any(skb);
>> +		return 0;
>> +	}
>> +
>> +	new_skb = netdev_alloc_skb_ip_align(ndev, PRUETH_MAX_PKT_SIZE);
>> +	/* if allocation fails we drop the packet but push the
>> +	 * descriptor back to the ring with old skb to prevent a stall
>> +	 */
>> +	if (!new_skb) {
>> +		ndev->stats.rx_dropped++;
>> +		new_skb = skb;
>> +	} else {
>> +		/* send the filled skb up the n/w stack */
>> +		skb_put(skb, pkt_len);
>> +		skb->protocol = eth_type_trans(skb, ndev);
>> +		netif_receive_skb(skb);
> 
> This is (apparently) in napi context. You should use napi_gro_receive()
> or napi_gro_frags()
> 

Here instead of the below line,
	netif_receive_skb(skb);
I will add the below line.
	napi_gro_receive(&emac->napi_rx,skb);

> 
> Cheers!
> 
> Paolo
> 
>

Thanks and Regards,
Md Danish Anwar.

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> Subject: Re: [PATCH v2 2/2] net: ti: icssg-prueth: Add ICSSG ethernet driver
> From: Paolo Abeni <pabeni@redhat.com>
> To: Puranjay Mohan <p-mohan@ti.com>, linux-kernel@vger.kernel.org
> Cc: davem@davemloft.net, edumazet@google.com,
>  krzysztof.kozlowski+dt@linaro.org,  netdev@vger.kernel.org,
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>  linux-arm-kernel@lists.infradead.org, rogerq@kernel.org, 
>  grygorii.strashko@ti.com, vigneshr@ti.com, kishon@ti.com,
>  robh+dt@kernel.org,  afd@ti.com, andrew@lunn.ch
> Date: Tue, 31 May 2022 13:23:40 +0200
> In-Reply-To: <20220531095108.21757-3-p-mohan@ti.com>
> References: <20220531095108.21757-1-p-mohan@ti.com>
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> 
> On Tue, 2022-05-31 at 15:21 +0530, Puranjay Mohan wrote:
> [...]
>> +static int emac_tx_complete_packets(struct prueth_emac *emac, int chn,
>> +				    int budget)
>> +{
>> +	struct net_device *ndev = emac->ndev;
>> +	struct cppi5_host_desc_t *desc_tx;
>> +	struct netdev_queue *netif_txq;
>> +	struct prueth_tx_chn *tx_chn;
>> +	unsigned int total_bytes = 0;
>> +	struct sk_buff *skb;
>> +	dma_addr_t desc_dma;
>> +	int res, num_tx = 0;
>> +	void **swdata;
>> +
>> +	tx_chn = &emac->tx_chns[chn];
>> +
>> +	while (budget--) {
>> +		res = k3_udma_glue_pop_tx_chn(tx_chn->tx_chn, &desc_dma);
>> +		if (res == -ENODATA)
>> +			break;
>> +
>> +		/* teardown completion */
>> +		if (cppi5_desc_is_tdcm(desc_dma)) {
>> +			if (atomic_dec_and_test(&emac->tdown_cnt))
>> +				complete(&emac->tdown_complete);
>> +			break;
>> +		}
>> +
>> +		desc_tx = k3_cppi_desc_pool_dma2virt(tx_chn->desc_pool,
>> +						     desc_dma);
>> +		swdata = cppi5_hdesc_get_swdata(desc_tx);
>> +
>> +		skb = *(swdata);
>> +		prueth_xmit_free(tx_chn, desc_tx);
>> +
>> +		ndev = skb->dev;
>> +		ndev->stats.tx_packets++;
>> +		ndev->stats.tx_bytes += skb->len;
>> +		total_bytes += skb->len;
>> +		napi_consume_skb(skb, budget);
> 
> The above is uncorrect. In this loop's last iteration 'budget' will  be
> 0 and napi_consume_skb will wrongly assume the caller is not in NAPI
> context. 
> 
>> +static int prueth_dma_rx_push(struct prueth_emac *emac,
>> +			      struct sk_buff *skb,
>> +			      struct prueth_rx_chn *rx_chn)
>> +{
>> +	struct cppi5_host_desc_t *desc_rx;
>> +	struct net_device *ndev = emac->ndev;
>> +	dma_addr_t desc_dma;
>> +	dma_addr_t buf_dma;
>> +	u32 pkt_len = skb_tailroom(skb);
>> +	void **swdata;
>> +
>> +	desc_rx = k3_cppi_desc_pool_alloc(rx_chn->desc_pool);
>> +	if (!desc_rx) {
>> +		netdev_err(ndev, "rx push: failed to allocate descriptor\n");
>> +		return -ENOMEM;
>> +	}
>> +	desc_dma = k3_cppi_desc_pool_virt2dma(rx_chn->desc_pool, desc_rx);
>> +
>> +	buf_dma = dma_map_single(rx_chn->dma_dev, skb->data, pkt_len, DMA_FROM_DEVICE);
>> +	if (unlikely(dma_mapping_error(rx_chn->dma_dev, buf_dma))) {
>> +		k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>> +		netdev_err(ndev, "rx push: failed to map rx pkt buffer\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	cppi5_hdesc_init(desc_rx, CPPI5_INFO0_HDESC_EPIB_PRESENT,
>> +			 PRUETH_NAV_PS_DATA_SIZE);
>> +	k3_udma_glue_rx_dma_to_cppi5_addr(rx_chn->rx_chn, &buf_dma);
>> +	cppi5_hdesc_attach_buf(desc_rx, buf_dma, skb_tailroom(skb), buf_dma, skb_tailroom(skb));
>> +
>> +	swdata = cppi5_hdesc_get_swdata(desc_rx);
>> +	*swdata = skb;
>> +
>> +	return k3_udma_glue_push_rx_chn(rx_chn->rx_chn, 0,
>> +					desc_rx, desc_dma);
>> +}
>> +
>> +static int emac_rx_packet(struct prueth_emac *emac, u32 flow_id)
>> +{
>> +	struct prueth_rx_chn *rx_chn = &emac->rx_chns;
>> +	struct net_device *ndev = emac->ndev;
>> +	struct cppi5_host_desc_t *desc_rx;
>> +	dma_addr_t desc_dma, buf_dma;
>> +	u32 buf_dma_len, pkt_len, port_id = 0;
>> +	int ret;
>> +	void **swdata;
>> +	struct sk_buff *skb, *new_skb;
>> +
>> +	ret = k3_udma_glue_pop_rx_chn(rx_chn->rx_chn, flow_id, &desc_dma);
>> +	if (ret) {
>> +		if (ret != -ENODATA)
>> +			netdev_err(ndev, "rx pop: failed: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	if (cppi5_desc_is_tdcm(desc_dma)) /* Teardown ? */
>> +		return 0;
>> +
>> +	desc_rx = k3_cppi_desc_pool_dma2virt(rx_chn->desc_pool, desc_dma);
>> +
>> +	swdata = cppi5_hdesc_get_swdata(desc_rx);
>> +	skb = *swdata;
>> +
>> +	cppi5_hdesc_get_obuf(desc_rx, &buf_dma, &buf_dma_len);
>> +	k3_udma_glue_rx_cppi5_to_dma_addr(rx_chn->rx_chn, &buf_dma);
>> +	pkt_len = cppi5_hdesc_get_pktlen(desc_rx);
>> +	/* firmware adds 4 CRC bytes, strip them */
>> +	pkt_len -= 4;
>> +	cppi5_desc_get_tags_ids(&desc_rx->hdr, &port_id, NULL);
>> +
>> +	dma_unmap_single(rx_chn->dma_dev, buf_dma, buf_dma_len, DMA_FROM_DEVICE);
>> +	k3_cppi_desc_pool_free(rx_chn->desc_pool, desc_rx);
>> +
>> +	skb->dev = ndev;
>> +	if (!netif_running(skb->dev)) {
>> +		dev_kfree_skb_any(skb);
>> +		return 0;
>> +	}
>> +
>> +	new_skb = netdev_alloc_skb_ip_align(ndev, PRUETH_MAX_PKT_SIZE);
>> +	/* if allocation fails we drop the packet but push the
>> +	 * descriptor back to the ring with old skb to prevent a stall
>> +	 */
>> +	if (!new_skb) {
>> +		ndev->stats.rx_dropped++;
>> +		new_skb = skb;
>> +	} else {
>> +		/* send the filled skb up the n/w stack */
>> +		skb_put(skb, pkt_len);
>> +		skb->protocol = eth_type_trans(skb, ndev);
>> +		netif_receive_skb(skb);
> 
> This is (apparently) in napi context. You should use napi_gro_receive()
> or napi_gro_frags()
> 
> 
> Cheers!
> 
> Paolo
> 
> 
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> 
>