[PATCH net-next 2/9] s390/qeth: also use TX NAPI for non-IQD devices

Julian Wiedmann
2021-06-11T07:35:42Z

Set scan_threshold = 0 to opt out from the qdio layer's internal tasklet
& timer mechanism for TX completions, and replace it with the TX NAPI
infrastructure that qeth already uses for IQD devices. This avoids the
fragile logic in qdio_check_output_queue(), enables tighter integration
and gives us more tuning options via ethtool in the future.

For now we continue to apply the same policy as the qdio layer:
scan for completions if 32 TX buffers are in use, or after 1 sec.
A re-scan is done after 10 sec, but only if no TX interrupt is pending.

With scan_threshold = 0 we no longer get TX completion scans from
within qdio_get_next_buffers(). So trigger these manually in qeth_poll()
and in the RX path switch to the equivalent qdio_inspect_queue().

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
drivers/s390/net/qeth_core.h | 6 ++
drivers/s390/net/qeth_core_main.c | 148 +++++++++++++++---------------
2 files changed, 79 insertions(+), 75 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index 3a49ef8dd906..4d29801bcf41 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -527,6 +527,7 @@ struct qeth_qdio_out_q {

unsigned int coalesce_usecs;
unsigned int max_coalesced_frames;
+ unsigned int rescan_usecs;
};

#define qeth_for_each_output_queue(card, q, i) \
@@ -887,6 +888,11 @@ static inline bool qeth_card_hw_is_reachable(struct qeth_card *card)
return card->state == CARD_STATE_SOFTSETUP;
}

+static inline bool qeth_use_tx_irqs(struct qeth_card *card)
+{
+ return !IS_IQD(card);
+}
+
static inline void qeth_unlock_channel(struct qeth_card *card,
struct qeth_channel *channel)
{
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 9085f22ca34c..f22f223a4a6c 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -2665,8 +2665,15 @@ static int qeth_alloc_qdio_queues(struct qeth_card *card)
INIT_LIST_HEAD(&queue->pending_bufs);
spin_lock_init(&queue->lock);
timer_setup(&queue->timer, qeth_tx_completion_timer, 0);
- queue->coalesce_usecs = QETH_TX_COALESCE_USECS;
- queue->max_coalesced_frames = QETH_TX_MAX_COALESCED_FRAMES;
+ if (IS_IQD(card)) {
+ queue->coalesce_usecs = QETH_TX_COALESCE_USECS;
+ queue->max_coalesced_frames = QETH_TX_MAX_COALESCED_FRAMES;
+ queue->rescan_usecs = QETH_TX_TIMER_USECS;
+ } else {
+ queue->coalesce_usecs = USEC_PER_SEC;
+ queue->max_coalesced_frames = 0;
+ queue->rescan_usecs = 10 * USEC_PER_SEC;
+ }
queue->priority = QETH_QIB_PQUE_PRIO_DEFAULT;
}

@@ -3603,8 +3610,8 @@ static void qeth_flush_buffers(struct qeth_qdio_out_q *queue, int index,
int count)
{
struct qeth_qdio_out_buffer *buf = queue->bufs[index];
- unsigned int qdio_flags = QDIO_FLAG_SYNC_OUTPUT;
struct qeth_card *card = queue->card;
+ unsigned int frames, usecs;
struct qaob *aob = NULL;
int rc;
int i;
@@ -3660,14 +3667,11 @@ static void qeth_flush_buffers(struct qeth_qdio_out_q *queue, int index,
buf->buffer->element[0].sflags |= SBAL_SFLAGS0_PCI_REQ;
}
}
-
- if (atomic_read(&queue->set_pci_flags_count))
- qdio_flags |= QDIO_FLAG_PCI_OUT;
}

QETH_TXQ_STAT_INC(queue, doorbell);
- rc = do_QDIO(CARD_DDEV(card), qdio_flags, queue->queue_no, index, count,
- aob);
+ rc = do_QDIO(CARD_DDEV(card), QDIO_FLAG_SYNC_OUTPUT, queue->queue_no,
+ index, count, aob);

switch (rc) {
case 0:
@@ -3675,17 +3679,20 @@ static void qeth_flush_buffers(struct qeth_qdio_out_q *queue, int index,
/* ignore temporary SIGA errors without busy condition */

/* Fake the TX completion interrupt: */
- if (IS_IQD(card)) {
- unsigned int frames = READ_ONCE(queue->max_coalesced_frames);
- unsigned int usecs = READ_ONCE(queue->coalesce_usecs);
+ frames = READ_ONCE(queue->max_coalesced_frames);
+ usecs = READ_ONCE(queue->coalesce_usecs);

- if (frames && queue->coalesced_frames >= frames) {
- napi_schedule(&queue->napi);
- queue->coalesced_frames = 0;
- QETH_TXQ_STAT_INC(queue, coal_frames);
- } else if (usecs) {
- qeth_tx_arm_timer(queue, usecs);
- }
+ if (frames && queue->coalesced_frames >= frames) {
+ napi_schedule(&queue->napi);
+ queue->coalesced_frames = 0;
+ QETH_TXQ_STAT_INC(queue, coal_frames);
+ } else if (qeth_use_tx_irqs(card) &&
+ atomic_read(&queue->used_buffers) >= 32) {
+ /* Old behaviour carried over from the qdio layer: */
+ napi_schedule(&queue->napi);
+ QETH_TXQ_STAT_INC(queue, coal_frames);
+ } else if (usecs) {
+ qeth_tx_arm_timer(queue, usecs);
}

break;
@@ -3833,36 +3840,14 @@ static void qeth_qdio_output_handler(struct ccw_device *ccwdev,
unsigned long card_ptr)
{
struct qeth_card *card = (struct qeth_card *) card_ptr;
- struct qeth_qdio_out_q *queue = card->qdio.out_qs[__queue];
struct net_device *dev = card->dev;
- struct netdev_queue *txq;
- int i;

QETH_CARD_TEXT(card, 6, "qdouhdl");
if (qdio_error & QDIO_ERROR_FATAL) {
QETH_CARD_TEXT(card, 2, "achkcond");
netif_tx_stop_all_queues(dev);
qeth_schedule_recovery(card);
- return;
- }
-
- for (i = first_element; i < (first_element + count); ++i) {
- struct qeth_qdio_out_buffer *buf = queue->bufs[QDIO_BUFNR(i)];
-
- qeth_handle_send_error(card, buf, qdio_error);
- qeth_clear_output_buffer(queue, buf, qdio_error, 0);
}
-
- atomic_sub(count, &queue->used_buffers);
- qeth_check_outbound_queue(queue);
-
- txq = netdev_get_tx_queue(dev, __queue);
- /* xmit may have observed the full-condition, but not yet stopped the
- * txq. In which case the code below won't trigger. So before returning,
- * xmit will re-check the txq's fill level and wake it up if needed.
- */
- if (netif_tx_queue_stopped(txq) && !qeth_out_queue_is_full(queue))
- netif_tx_wake_queue(txq);
}

/**
@@ -5258,7 +5243,6 @@ static int qeth_qdio_establish(struct qeth_card *card)
init_data.int_parm = (unsigned long) card;
init_data.input_sbal_addr_array = in_sbal_ptrs;
init_data.output_sbal_addr_array = out_sbal_ptrs;
- init_data.scan_threshold = IS_IQD(card) ? 0 : 32;

if (atomic_cmpxchg(&card->qdio.state, QETH_QDIO_ALLOCATED,
QETH_QDIO_ESTABLISHED) == QETH_QDIO_ALLOCATED) {
@@ -5958,9 +5942,10 @@ static unsigned int qeth_rx_poll(struct qeth_card *card, int budget)
/* Fetch completed RX buffers: */
if (!card->rx.b_count) {
card->rx.qdio_err = 0;
- card->rx.b_count = qdio_get_next_buffers(
- card->data.ccwdev, 0, &card->rx.b_index,
- &card->rx.qdio_err);
+ card->rx.b_count = qdio_inspect_queue(CARD_DDEV(card),
+ 0, true,
+ &card->rx.b_index,
+ &card->rx.qdio_err);
if (card->rx.b_count <= 0) {
card->rx.b_count = 0;
break;
@@ -6024,6 +6009,16 @@ int qeth_poll(struct napi_struct *napi, int budget)

work_done = qeth_rx_poll(card, budget);

+ if (qeth_use_tx_irqs(card)) {
+ struct qeth_qdio_out_q *queue;
+ unsigned int i;
+
+ qeth_for_each_output_queue(card, queue, i) {
+ if (!qeth_out_queue_is_empty(queue))
+ napi_schedule(&queue->napi);
+ }
+ }
+
if (card->options.cq == QETH_CQ_ENABLED)
qeth_cq_poll(card);

@@ -6140,7 +6135,10 @@ static int qeth_tx_poll(struct napi_struct *napi, int budget)
unsigned int work_done = 0;
struct netdev_queue *txq;

- txq = netdev_get_tx_queue(dev, qeth_iqd_translate_txq(dev, queue_no));
+ if (IS_IQD(card))
+ txq = netdev_get_tx_queue(dev, qeth_iqd_translate_txq(dev, queue_no));
+ else
+ txq = netdev_get_tx_queue(dev, queue_no);

while (1) {
unsigned int start, error, i;
@@ -6167,8 +6165,9 @@ static int qeth_tx_poll(struct napi_struct *napi, int budget)
&start, &error);
if (completed <= 0) {
/* Ensure we see TX completion for pending work: */
- if (napi_complete_done(napi, 0))
- qeth_tx_arm_timer(queue, QETH_TX_TIMER_USECS);
+ if (napi_complete_done(napi, 0) &&
+ !atomic_read(&queue->set_pci_flags_count))
+ qeth_tx_arm_timer(queue, queue->rescan_usecs);
return 0;
}

@@ -6181,12 +6180,19 @@ static int qeth_tx_poll(struct napi_struct *napi, int budget)
bytes += buffer->bytes;

qeth_handle_send_error(card, buffer, error);
- qeth_iqd_tx_complete(queue, bidx, error, budget);
+ if (IS_IQD(card))
+ qeth_iqd_tx_complete(queue, bidx, error, budget);
+ else
+ qeth_clear_output_buffer(queue, buffer, error,
+ budget);
}

- netdev_tx_completed_queue(txq, packets, bytes);
atomic_sub(completed, &queue->used_buffers);
work_done += completed;
+ if (IS_IQD(card))
+ netdev_tx_completed_queue(txq, packets, bytes);
+ else
+ qeth_check_outbound_queue(queue);

/* xmit may have observed the full-condition, but not yet
* stopped the txq. In which case the code below won't trigger.
@@ -7230,6 +7236,8 @@ EXPORT_SYMBOL_GPL(qeth_iqd_select_queue);
int qeth_open(struct net_device *dev)
{
struct qeth_card *card = dev->ml_priv;
+ struct qeth_qdio_out_q *queue;
+ unsigned int i;

QETH_CARD_TEXT(card, 4, "qethopen");

@@ -7237,16 +7245,11 @@ int qeth_open(struct net_device *dev)
netif_tx_start_all_queues(dev);

local_bh_disable();
- if (IS_IQD(card)) {
- struct qeth_qdio_out_q *queue;
- unsigned int i;
-
- qeth_for_each_output_queue(card, queue, i) {
- netif_tx_napi_add(dev, &queue->napi, qeth_tx_poll,
- QETH_NAPI_WEIGHT);
- napi_enable(&queue->napi);
- napi_schedule(&queue->napi);
- }
+ qeth_for_each_output_queue(card, queue, i) {
+ netif_tx_napi_add(dev, &queue->napi, qeth_tx_poll,
+ QETH_NAPI_WEIGHT);
+ napi_enable(&queue->napi);
+ napi_schedule(&queue->napi);
}

napi_enable(&card->napi);
@@ -7261,6 +7264,8 @@ EXPORT_SYMBOL_GPL(qeth_open);
int qeth_stop(struct net_device *dev)
{
struct qeth_card *card = dev->ml_priv;
+ struct qeth_qdio_out_q *queue;
+ unsigned int i;

QETH_CARD_TEXT(card, 4, "qethstop");

@@ -7268,24 +7273,17 @@ int qeth_stop(struct net_device *dev)
cancel_delayed_work_sync(&card->buffer_reclaim_work);
qdio_stop_irq(CARD_DDEV(card));

- if (IS_IQD(card)) {
- struct qeth_qdio_out_q *queue;
- unsigned int i;
-
- /* Quiesce the NAPI instances: */
- qeth_for_each_output_queue(card, queue, i)
- napi_disable(&queue->napi);
+ /* Quiesce the NAPI instances: */
+ qeth_for_each_output_queue(card, queue, i)
+ napi_disable(&queue->napi);

- /* Stop .ndo_start_xmit, might still access queue->napi. */
- netif_tx_disable(dev);
+ /* Stop .ndo_start_xmit, might still access queue->napi. */
+ netif_tx_disable(dev);

- qeth_for_each_output_queue(card, queue, i) {
- del_timer_sync(&queue->timer);
- /* Queues may get re-allocated, so remove the NAPIs. */
- netif_napi_del(&queue->napi);
- }
- } else {
- netif_tx_disable(dev);
+ qeth_for_each_output_queue(card, queue, i) {
+ del_timer_sync(&queue->timer);
+ /* Queues may get re-allocated, so remove the NAPIs. */
+ netif_napi_del(&queue->napi);
}

return 0;
--
2.25.1