Commit 9c159bbc authored by Julian Wiedmann's avatar Julian Wiedmann Committed by Vasily Gorbik
Browse files

s390/qdio: clear DSCI early for polling drivers 



Polling drivers in a configuration with 1 Input Queue currently keep
their DSCI armed all the way through the poll cycle, until
qdio_start_irq() clears it.

_Any_ intermittent QDIO interrupt delivered to tiqdio_thinint_handler()
will thus cause
1) the 'adapter_int' statistic to be incremented,
2) a call to tiqdio_call_inq_handlers() for this device, and then
3) the 'int_discarded' statistics to be incremented.

This causes overhead & complexity in the IRQ path, along with ambiguity
in the statistics.
On the other hand the device should be in IRQ avoidance mode during a
poll cycle, so there won't be a lot of DSCI ping-pong that this
micro-optimization could prevent.

So align the DSCI handling with what we already do for devices with
multiple Input Queues: clear it right away while processing the IRQ.

For the non-polling path this means that we no longer need to handle
the 1-queue case separately.

Signed-off-by: default avatarJulian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: default avatarBenjamin Block <bblock@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent a8a4ee27

drivers/s390/cio/qdio.h

+0 −1
Original line number Diff line number Diff line
@@ -374,7 +374,6 @@ int tiqdio_allocate_memory(void); 
void tiqdio_free_memory(void);

int tiqdio_register_thinints(void);

void tiqdio_unregister_thinints(void);

void clear_nonshared_ind(struct qdio_irq *);

int test_nonshared_ind(struct qdio_irq *);



/* prototypes for setup */

drivers/s390/cio/qdio_main.c

+0 −2
Original line number Diff line number Diff line
@@ -1643,8 +1643,6 @@ int qdio_start_irq(struct ccw_device *cdev) 
	if (!irq_ptr)

		return -ENODEV;



	clear_nonshared_ind(irq_ptr);



	for_each_input_queue(irq_ptr, q, i)

		qdio_stop_polling(q);

drivers/s390/cio/qdio_thinint.c

+2 −23
Original line number Diff line number Diff line
@@ -82,32 +82,16 @@ void tiqdio_remove_device(struct qdio_irq *irq_ptr) 
	INIT_LIST_HEAD(&irq_ptr->entry);

}



static inline int has_multiple_inq_on_dsci(struct qdio_irq *irq_ptr)

{

	return irq_ptr->nr_input_qs > 1;

}



static inline int references_shared_dsci(struct qdio_irq *irq_ptr)

{

	return irq_ptr->dsci == &q_indicators[TIQDIO_SHARED_IND].ind;

}



void clear_nonshared_ind(struct qdio_irq *irq_ptr)

{

	if (!is_thinint_irq(irq_ptr))

		return;

	if (references_shared_dsci(irq_ptr) ||

	    has_multiple_inq_on_dsci(irq_ptr))

		return;

	xchg(irq_ptr->dsci, 0);

}



int test_nonshared_ind(struct qdio_irq *irq_ptr)

{

	if (!is_thinint_irq(irq_ptr))

		return 0;

	if (references_shared_dsci(irq_ptr) ||

	    has_multiple_inq_on_dsci(irq_ptr))

	if (references_shared_dsci(irq_ptr))

		return 0;

	if (*irq_ptr->dsci)

		return 1;
@@ -127,8 +111,7 @@ static inline void tiqdio_call_inq_handlers(struct qdio_irq *irq) 
	struct qdio_q *q;

	int i;



	if (!references_shared_dsci(irq) &&

	    has_multiple_inq_on_dsci(irq))

	if (!references_shared_dsci(irq))

		xchg(irq->dsci, 0);



	if (irq->irq_poll) {
@@ -140,10 +123,6 @@ static inline void tiqdio_call_inq_handlers(struct qdio_irq *irq) 
		return;

	}



	if (!references_shared_dsci(irq) &&

	    !has_multiple_inq_on_dsci(irq))

		xchg(irq->dsci, 0);



	for_each_input_queue(irq, q, i) {

		/*

		 * Call inbound processing but not directly

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