Commit f9b53bb1 authored by Song Yoong Siang's avatar Song Yoong Siang Committed by Martin KaFai Lau
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igc: Refactor empty frame insertion for launch time support 



Refactor the code for inserting an empty frame into a new function
igc_insert_empty_frame(). This change extracts the logic for inserting
an empty packet from igc_xmit_frame_ring() into a separate function,
allowing it to be reused in future implementations, such as the XDP
zero copy transmit function.

Remove the igc_desc_unused() checking in igc_init_tx_empty_descriptor()
because the number of descriptors needed is guaranteed.

Ensure that skb allocation and DMA mapping work for the empty frame,
before proceeding to fill in igc_tx_buffer info, context descriptor,
and data descriptor.

Rate limit the error messages for skb allocation and DMA mapping failures.

Update the comment to indicate that the 2 descriptors needed by the empty
frame are already taken into consideration in igc_xmit_frame_ring().

Handle the case where the insertion of an empty frame fails and explain
the reason behind this handling.

Signed-off-by: default avatarSong Yoong Siang <yoong.siang.song@intel.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: default avatarFaizal Rahim <faizal.abdul.rahim@linux.intel.com>
Reviewed-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20250216093430.957880-5-yoong.siang.song@intel.com
parent 04f64dea

drivers/net/ethernet/intel/igc/igc_main.c

+50 −32
Original line number Diff line number Diff line
@@ -1092,7 +1092,8 @@ static int igc_init_empty_frame(struct igc_ring *ring, 


	dma = dma_map_single(ring->dev, skb->data, size, DMA_TO_DEVICE);

	if (dma_mapping_error(ring->dev, dma)) {

		netdev_err_once(ring->netdev, "Failed to map DMA for TX\n");

		net_err_ratelimited("%s: DMA mapping error for empty frame\n",

				    netdev_name(ring->netdev));

		return -ENOMEM;

	}
@@ -1108,20 +1109,12 @@ static int igc_init_empty_frame(struct igc_ring *ring, 
	return 0;

}



static int igc_init_tx_empty_descriptor(struct igc_ring *ring,

static void igc_init_tx_empty_descriptor(struct igc_ring *ring,

					 struct sk_buff *skb,

					 struct igc_tx_buffer *first)

{

	union igc_adv_tx_desc *desc;

	u32 cmd_type, olinfo_status;

	int err;



	if (!igc_desc_unused(ring))

		return -EBUSY;



	err = igc_init_empty_frame(ring, first, skb);

	if (err)

		return err;



	cmd_type = IGC_ADVTXD_DTYP_DATA | IGC_ADVTXD_DCMD_DEXT |

		   IGC_ADVTXD_DCMD_IFCS | IGC_TXD_DCMD |
@@ -1140,8 +1133,6 @@ static int igc_init_tx_empty_descriptor(struct igc_ring *ring, 
	ring->next_to_use++;

	if (ring->next_to_use == ring->count)

		ring->next_to_use = 0;



	return 0;

}



#define IGC_EMPTY_FRAME_SIZE 60
@@ -1567,6 +1558,40 @@ static bool igc_request_tx_tstamp(struct igc_adapter *adapter, struct sk_buff *s 
	return false;

}



static int igc_insert_empty_frame(struct igc_ring *tx_ring)

{

	struct igc_tx_buffer *empty_info;

	struct sk_buff *empty_skb;

	void *data;

	int ret;



	empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];

	empty_skb = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);

	if (unlikely(!empty_skb)) {

		net_err_ratelimited("%s: skb alloc error for empty frame\n",

				    netdev_name(tx_ring->netdev));

		return -ENOMEM;

	}



	data = skb_put(empty_skb, IGC_EMPTY_FRAME_SIZE);

	memset(data, 0, IGC_EMPTY_FRAME_SIZE);



	/* Prepare DMA mapping and Tx buffer information */

	ret = igc_init_empty_frame(tx_ring, empty_info, empty_skb);

	if (unlikely(ret)) {

		dev_kfree_skb_any(empty_skb);

		return ret;

	}



	/* Prepare advanced context descriptor for empty packet */

	igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);



	/* Prepare advanced data descriptor for empty packet */

	igc_init_tx_empty_descriptor(tx_ring, empty_skb, empty_info);



	return 0;

}



static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,

				       struct igc_ring *tx_ring)

{
@@ -1586,6 +1611,7 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb, 
	 *	+ 1 desc for skb_headlen/IGC_MAX_DATA_PER_TXD,

	 *	+ 2 desc gap to keep tail from touching head,

	 *	+ 1 desc for context descriptor,

	 *	+ 2 desc for inserting an empty packet for launch time,

	 * otherwise try next time

	 */

	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
@@ -1605,24 +1631,16 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb, 
	launch_time = igc_tx_launchtime(tx_ring, txtime, &first_flag, &insert_empty);



	if (insert_empty) {

		struct igc_tx_buffer *empty_info;

		struct sk_buff *empty;

		void *data;



		empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];

		empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);

		if (!empty)

			goto done;



		data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);

		memset(data, 0, IGC_EMPTY_FRAME_SIZE);



		igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);



		if (igc_init_tx_empty_descriptor(tx_ring,

						 empty,

						 empty_info) < 0)

			dev_kfree_skb_any(empty);

		/* Reset the launch time if the required empty frame fails to

		 * be inserted. However, this packet is not dropped, so it

		 * "dirties" the current Qbv cycle. This ensures that the

		 * upcoming packet, which is scheduled in the next Qbv cycle,

		 * does not require an empty frame. This way, the launch time

		 * continues to function correctly despite the current failure

		 * to insert the empty frame.

		 */

		if (igc_insert_empty_frame(tx_ring))

			launch_time = 0;

	}



done: