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Message-ID: <d9b43956-5b7f-80f7-5638-4744fe96e0f2@solarflare.com>
Date: Thu, 5 Mar 2020 13:49:05 +0000
From: Martin Habets <mhabets@...arflare.com>
To: Tom Zhao <tzhao@...arflare.com>,
<linux-net-drivers@...arflare.com>, <netdev@...r.kernel.org>,
<davem@...emloft.net>
Subject: Re: [PATCH] sfc: complete the next packet when we receive a timestamp
On 05/03/2020 11:38, Tom Zhao wrote:
> We now ignore the "completion" event when using tx queue timestamping,
> and only pay attention to the two (high and low) timestamp events. The
> NIC will send a pair of timestamp events for every packet transmitted.
> The current firmware may merge the completion events, and it is possible
> that future versions may reorder the completion and timestamp events.
> As such the completion event is not useful.
>
> Without this patch in place a merged completion event on a queue with
> timestamping will cause a "spurious TX completion" error. This affects
> SFN8000-series adapters.
>
> Signed-off-by: Tom Zhao <tzhao@...arflare.com>
Acked-by: Martin Habets <mhabets@...arflare.com>
> ---
> v2: apply to correct head
> v3: actually send the right patch this time
> ---
> drivers/net/ethernet/sfc/ef10.c | 32 +++++++++++-----------
> drivers/net/ethernet/sfc/efx.h | 1 +
> drivers/net/ethernet/sfc/net_driver.h | 3 ---
> drivers/net/ethernet/sfc/tx.c | 38 +++++++++++++++++++++++++++
> drivers/net/ethernet/sfc/tx_common.c | 29 +++++++++++---------
> drivers/net/ethernet/sfc/tx_common.h | 6 +++++
> 6 files changed, 78 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/net/ethernet/sfc/ef10.c b/drivers/net/ethernet/sfc/ef10.c
> index 52113b7529d6..3f16bd807c6e 100644
> --- a/drivers/net/ethernet/sfc/ef10.c
> +++ b/drivers/net/ethernet/sfc/ef10.c
> @@ -2853,11 +2853,24 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
> }
>
> /* Transmit timestamps are only available for 8XXX series. They result
> - * in three events per packet. These occur in order, and are:
> - * - the normal completion event
> + * in up to three events per packet. These occur in order, and are:
> + * - the normal completion event (may be omitted)
> * - the low part of the timestamp
> * - the high part of the timestamp
> *
> + * It's possible for multiple completion events to appear before the
> + * corresponding timestamps. So we can for example get:
> + * COMP N
> + * COMP N+1
> + * TS_LO N
> + * TS_HI N
> + * TS_LO N+1
> + * TS_HI N+1
> + *
> + * In addition it's also possible for the adjacent completions to be
> + * merged, so we may not see COMP N above. As such, the completion
> + * events are not very useful here.
> + *
> * Each part of the timestamp is itself split across two 16 bit
> * fields in the event.
> */
> @@ -2865,17 +2878,7 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
>
> switch (tx_ev_type) {
> case TX_TIMESTAMP_EVENT_TX_EV_COMPLETION:
> - /* In case of Queue flush or FLR, we might have received
> - * the previous TX completion event but not the Timestamp
> - * events.
> - */
> - if (tx_queue->completed_desc_ptr != tx_queue->ptr_mask)
> - efx_xmit_done(tx_queue, tx_queue->completed_desc_ptr);
> -
> - tx_ev_desc_ptr = EFX_QWORD_FIELD(*event,
> - ESF_DZ_TX_DESCR_INDX);
> - tx_queue->completed_desc_ptr =
> - tx_ev_desc_ptr & tx_queue->ptr_mask;
> + /* Ignore this event - see above. */
> break;
>
> case TX_TIMESTAMP_EVENT_TX_EV_TSTAMP_LO:
> @@ -2887,8 +2890,7 @@ efx_ef10_handle_tx_event(struct efx_channel *channel, efx_qword_t *event)
> ts_part = efx_ef10_extract_event_ts(event);
> tx_queue->completed_timestamp_major = ts_part;
>
> - efx_xmit_done(tx_queue, tx_queue->completed_desc_ptr);
> - tx_queue->completed_desc_ptr = tx_queue->ptr_mask;
> + efx_xmit_done_single(tx_queue);
> break;
>
> default:
> diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
> index da54afaa3c44..66dcab140449 100644
> --- a/drivers/net/ethernet/sfc/efx.h
> +++ b/drivers/net/ethernet/sfc/efx.h
> @@ -20,6 +20,7 @@ netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
> struct net_device *net_dev);
> netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb);
> void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index);
> +void efx_xmit_done_single(struct efx_tx_queue *tx_queue);
> int efx_setup_tc(struct net_device *net_dev, enum tc_setup_type type,
> void *type_data);
> extern unsigned int efx_piobuf_size;
> diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
> index 392bd5b7017e..b836315bac87 100644
> --- a/drivers/net/ethernet/sfc/net_driver.h
> +++ b/drivers/net/ethernet/sfc/net_driver.h
> @@ -208,8 +208,6 @@ struct efx_tx_buffer {
> * avoid cache-line ping-pong between the xmit path and the
> * completion path.
> * @merge_events: Number of TX merged completion events
> - * @completed_desc_ptr: Most recent completed pointer - only used with
> - * timestamping.
> * @completed_timestamp_major: Top part of the most recent tx timestamp.
> * @completed_timestamp_minor: Low part of the most recent tx timestamp.
> * @insert_count: Current insert pointer
> @@ -269,7 +267,6 @@ struct efx_tx_queue {
> unsigned int merge_events;
> unsigned int bytes_compl;
> unsigned int pkts_compl;
> - unsigned int completed_desc_ptr;
> u32 completed_timestamp_major;
> u32 completed_timestamp_minor;
>
> diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
> index 696a77c20cb7..19b58563cb78 100644
> --- a/drivers/net/ethernet/sfc/tx.c
> +++ b/drivers/net/ethernet/sfc/tx.c
> @@ -534,6 +534,44 @@ netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
> return efx_enqueue_skb(tx_queue, skb);
> }
>
> +void efx_xmit_done_single(struct efx_tx_queue *tx_queue)
> +{
> + unsigned int pkts_compl = 0, bytes_compl = 0;
> + unsigned int read_ptr;
> + bool finished = false;
> +
> + read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
> +
> + while (!finished) {
> + struct efx_tx_buffer *buffer = &tx_queue->buffer[read_ptr];
> +
> + if (!efx_tx_buffer_in_use(buffer)) {
> + struct efx_nic *efx = tx_queue->efx;
> +
> + netif_err(efx, hw, efx->net_dev,
> + "TX queue %d spurious single TX completion\n",
> + tx_queue->queue);
> + efx_schedule_reset(efx, RESET_TYPE_TX_SKIP);
> + return;
> + }
> +
> + /* Need to check the flag before dequeueing. */
> + if (buffer->flags & EFX_TX_BUF_SKB)
> + finished = true;
> + efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
> +
> + ++tx_queue->read_count;
> + read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
> + }
> +
> + tx_queue->pkts_compl += pkts_compl;
> + tx_queue->bytes_compl += bytes_compl;
> +
> + EFX_WARN_ON_PARANOID(pkts_compl != 1);
> +
> + efx_xmit_done_check_empty(tx_queue);
> +}
> +
> void efx_init_tx_queue_core_txq(struct efx_tx_queue *tx_queue)
> {
> struct efx_nic *efx = tx_queue->efx;
> diff --git a/drivers/net/ethernet/sfc/tx_common.c b/drivers/net/ethernet/sfc/tx_common.c
> index b1571e9789d0..70876df1da69 100644
> --- a/drivers/net/ethernet/sfc/tx_common.c
> +++ b/drivers/net/ethernet/sfc/tx_common.c
> @@ -80,7 +80,6 @@ void efx_init_tx_queue(struct efx_tx_queue *tx_queue)
> tx_queue->xmit_more_available = false;
> tx_queue->timestamping = (efx_ptp_use_mac_tx_timestamps(efx) &&
> tx_queue->channel == efx_ptp_channel(efx));
> - tx_queue->completed_desc_ptr = tx_queue->ptr_mask;
> tx_queue->completed_timestamp_major = 0;
> tx_queue->completed_timestamp_minor = 0;
>
> @@ -210,10 +209,9 @@ static void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
> while (read_ptr != stop_index) {
> struct efx_tx_buffer *buffer = &tx_queue->buffer[read_ptr];
>
> - if (!(buffer->flags & EFX_TX_BUF_OPTION) &&
> - unlikely(buffer->len == 0)) {
> + if (!efx_tx_buffer_in_use(buffer)) {
> netif_err(efx, tx_err, efx->net_dev,
> - "TX queue %d spurious TX completion id %x\n",
> + "TX queue %d spurious TX completion id %d\n",
> tx_queue->queue, read_ptr);
> efx_schedule_reset(efx, RESET_TYPE_TX_SKIP);
> return;
> @@ -226,6 +224,19 @@ static void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
> }
> }
>
> +void efx_xmit_done_check_empty(struct efx_tx_queue *tx_queue)
> +{
> + if ((int)(tx_queue->read_count - tx_queue->old_write_count) >= 0) {
> + tx_queue->old_write_count = READ_ONCE(tx_queue->write_count);
> + if (tx_queue->read_count == tx_queue->old_write_count) {
> + /* Ensure that read_count is flushed. */
> + smp_mb();
> + tx_queue->empty_read_count =
> + tx_queue->read_count | EFX_EMPTY_COUNT_VALID;
> + }
> + }
> +}
> +
> void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
> {
> unsigned int fill_level, pkts_compl = 0, bytes_compl = 0;
> @@ -256,15 +267,7 @@ void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
> netif_tx_wake_queue(tx_queue->core_txq);
> }
>
> - /* Check whether the hardware queue is now empty */
> - if ((int)(tx_queue->read_count - tx_queue->old_write_count) >= 0) {
> - tx_queue->old_write_count = READ_ONCE(tx_queue->write_count);
> - if (tx_queue->read_count == tx_queue->old_write_count) {
> - smp_mb();
> - tx_queue->empty_read_count =
> - tx_queue->read_count | EFX_EMPTY_COUNT_VALID;
> - }
> - }
> + efx_xmit_done_check_empty(tx_queue);
> }
>
> /* Remove buffers put into a tx_queue for the current packet.
> diff --git a/drivers/net/ethernet/sfc/tx_common.h b/drivers/net/ethernet/sfc/tx_common.h
> index f92f1fe3a87f..99cf7ce2f36c 100644
> --- a/drivers/net/ethernet/sfc/tx_common.h
> +++ b/drivers/net/ethernet/sfc/tx_common.h
> @@ -21,6 +21,12 @@ void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
> unsigned int *pkts_compl,
> unsigned int *bytes_compl);
>
> +static inline bool efx_tx_buffer_in_use(struct efx_tx_buffer *buffer)
> +{
> + return buffer->len || (buffer->flags & EFX_TX_BUF_OPTION);
> +}
> +
> +void efx_xmit_done_check_empty(struct efx_tx_queue *tx_queue);
> void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index);
>
> void efx_enqueue_unwind(struct efx_tx_queue *tx_queue,
>
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