Commit 306a2782 authored by Ben Hutchings's avatar Ben Hutchings
Browse files

sfc: Separate out queue-empty check from efx_nic_may_push_tx_desc() 



Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
parent 183233be

drivers/net/ethernet/sfc/nic.h

+22 −6
Original line number Diff line number Diff line
@@ -71,6 +71,26 @@ efx_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index) 
	return ((efx_qword_t *) (tx_queue->txd.buf.addr)) + index;

}



/* Report whether the NIC considers this TX queue empty, given the

 * write_count used for the last doorbell push.  May return false

 * negative.

 */

static inline bool __efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue,

					 unsigned int write_count)

{

	unsigned int empty_read_count = ACCESS_ONCE(tx_queue->empty_read_count);



	if (empty_read_count == 0)

		return false;



	return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0;

}



static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue)

{

	return __efx_nic_tx_is_empty(tx_queue, tx_queue->write_count);

}



/* Decide whether to push a TX descriptor to the NIC vs merely writing

 * the doorbell.  This can reduce latency when we are adding a single

 * descriptor to an empty queue, but is otherwise pointless.  Further,
@@ -80,14 +100,10 @@ efx_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index) 
static inline bool efx_nic_may_push_tx_desc(struct efx_tx_queue *tx_queue,

					    unsigned int write_count)

{

	unsigned empty_read_count = ACCESS_ONCE(tx_queue->empty_read_count);



	if (empty_read_count == 0)

		return false;

	bool was_empty = __efx_nic_tx_is_empty(tx_queue, write_count);



	tx_queue->empty_read_count = 0;

	return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0

		&& tx_queue->write_count - write_count == 1;

	return was_empty && tx_queue->write_count - write_count == 1;

}



/* Returns a pointer to the specified descriptor in the RX descriptor queue */