sfc: Remove efx_rx_queue::add_lock

Ensure that efx_fast_push_rx_descriptors() must only run
from efx_process_channel() [NAPI], or when napi_disable()
has been executed.

Reimplement the slow fill by sending an event to the
channel, so that NAPI runs, and hanging the subsequent
fast fill off the event handler. Replace the sfc_refill
workqueue and delayed work items with a timer. We do
not need to stop this timer in efx_flush_all() because
it's safe to send the event always; receiving it will
be delayed until NAPI is restarted.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/sfc/efx.h b/drivers/net/sfc/efx.h
index ffd708c..e1e4488 100644
--- a/drivers/net/sfc/efx.h
+++ b/drivers/net/sfc/efx.h
@@ -47,12 +47,12 @@
 extern void efx_fini_rx_queue(struct efx_rx_queue *rx_queue);
 extern void efx_rx_strategy(struct efx_channel *channel);
 extern void efx_fast_push_rx_descriptors(struct efx_rx_queue *rx_queue);
-extern void efx_rx_work(struct work_struct *data);
+extern void efx_rx_slow_fill(unsigned long context);
 extern void __efx_rx_packet(struct efx_channel *channel,
 			    struct efx_rx_buffer *rx_buf, bool checksummed);
 extern void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
 			  unsigned int len, bool checksummed, bool discard);
-extern void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue, int delay);
+extern void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue);
 #define EFX_RXQ_SIZE 1024
 #define EFX_RXQ_MASK (EFX_RXQ_SIZE - 1)