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Commit 8b4c62ae authored by Michał Mirosław's avatar Michał Mirosław Committed by Felipe Balbi
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usb: gadget: u_serial: process RX in workqueue instead of tasklet 



Switch RX processing from tasklet to (delayed) work queue. This allows
receiver more room to process incoming data and prevents flood of
"ttyGS0: RX not scheduled?" messages on HS receive on slow CPU.

A side effect is 2.4MB/s zmodem transfer speed (up from 1.8MB/s)
on my test board.

Signed-off-by: default avatarMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
parent 539cf103

drivers/usb/gadget/function/u_serial.c

+14 −21
Original line number Diff line number Diff line
@@ -16,7 +16,6 @@ 


#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/interrupt.h>

#include <linux/device.h>

#include <linux/delay.h>

#include <linux/tty.h>
@@ -26,6 +25,7 @@ 
#include <linux/module.h>

#include <linux/console.h>

#include <linux/kthread.h>

#include <linux/workqueue.h>

#include <linux/kfifo.h>



#include "u_serial.h"
@@ -110,7 +110,7 @@ struct gs_port { 
	int read_allocated;

	struct list_head	read_queue;

	unsigned		n_read;

	struct tasklet_struct	push;

	struct delayed_work	push;



	struct list_head	write_pool;

	int write_started;
@@ -352,9 +352,10 @@ __acquires(&port->port_lock) 
 * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)

 * can be buffered before the TTY layer's buffers (currently 64 KB).

 */

static void gs_rx_push(unsigned long _port)

static void gs_rx_push(struct work_struct *work)

{

	struct gs_port		*port = (void *)_port;

	struct delayed_work	*w = to_delayed_work(work);

	struct gs_port		*port = container_of(w, struct gs_port, push);

	struct tty_struct	*tty;

	struct list_head	*queue = &port->read_queue;

	bool			disconnect = false;
@@ -429,21 +430,13 @@ static void gs_rx_push(unsigned long _port) 


	/* We want our data queue to become empty ASAP, keeping data

	 * in the tty and ldisc (not here).  If we couldn't push any

	 * this time around, there may be trouble unless there's an

	 * implicit tty_unthrottle() call on its way...

	 * this time around, RX may be starved, so wait until next jiffy.

	 *

	 * REVISIT we should probably add a timer to keep the tasklet

	 * from starving ... but it's not clear that case ever happens.

	 * We may leave non-empty queue only when there is a tty, and

	 * either it is throttled or there is no more room in flip buffer.

	 */

	if (!list_empty(queue) && tty) {

		if (!tty_throttled(tty)) {

			if (do_push)

				tasklet_schedule(&port->push);

			else

				pr_warn("ttyGS%d: RX not scheduled?\n",

					port->port_num);

		}

	}

	if (!list_empty(queue) && !tty_throttled(tty))

		schedule_delayed_work(&port->push, 1);



	/* If we're still connected, refill the USB RX queue. */

	if (!disconnect && port->port_usb)
@@ -459,7 +452,7 @@ static void gs_read_complete(struct usb_ep *ep, struct usb_request *req) 
	/* Queue all received data until the tty layer is ready for it. */

	spin_lock(&port->port_lock);

	list_add_tail(&req->list, &port->read_queue);

	tasklet_schedule(&port->push);

	schedule_delayed_work(&port->push, 0);

	spin_unlock(&port->port_lock);

}
@@ -854,8 +847,8 @@ static void gs_unthrottle(struct tty_struct *tty) 
		 * rts/cts, or other handshaking with the host, but if the

		 * read queue backs up enough we'll be NAKing OUT packets.

		 */

		tasklet_schedule(&port->push);

		pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);

		schedule_delayed_work(&port->push, 0);

	}

	spin_unlock_irqrestore(&port->port_lock, flags);

}
@@ -1159,7 +1152,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding) 
	init_waitqueue_head(&port->drain_wait);

	init_waitqueue_head(&port->close_wait);



	tasklet_init(&port->push, gs_rx_push, (unsigned long) port);

	INIT_DELAYED_WORK(&port->push, gs_rx_push);



	INIT_LIST_HEAD(&port->read_pool);

	INIT_LIST_HEAD(&port->read_queue);
@@ -1186,7 +1179,7 @@ static int gs_closed(struct gs_port *port) 


static void gserial_free_port(struct gs_port *port)

{

	tasklet_kill(&port->push);

	cancel_delayed_work_sync(&port->push);

	/* wait for old opens to finish */

	wait_event(port->close_wait, gs_closed(port));

	WARN_ON(port->port_usb != NULL);