diff options
| -rw-r--r-- | drivers/usb/gadget/u_serial.c | 236 |
1 files changed, 146 insertions, 90 deletions
diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c index abf9505d3a7..6641efa5563 100644 --- a/drivers/usb/gadget/u_serial.c +++ b/drivers/usb/gadget/u_serial.c @@ -52,6 +52,8 @@ * is managed in userspace ... OBEX, PTP, and MTP have been mentioned. */ +#define PREFIX "ttyGS" + /* * gserial is the lifecycle interface, used by USB functions * gs_port is the I/O nexus, used by the tty driver @@ -100,6 +102,8 @@ struct gs_port { wait_queue_head_t close_wait; /* wait for last close */ struct list_head read_pool; + struct list_head read_queue; + unsigned n_read; struct tasklet_struct push; struct list_head write_pool; @@ -367,11 +371,9 @@ __acquires(&port->port_lock) req->length = len; list_del(&req->list); -#ifdef VERBOSE_DEBUG - pr_debug("%s: %s, len=%d, 0x%02x 0x%02x 0x%02x ...\n", - __func__, in->name, len, *((u8 *)req->buf), + pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n", + port->port_num, len, *((u8 *)req->buf), *((u8 *)req->buf+1), *((u8 *)req->buf+2)); -#endif /* Drop lock while we call out of driver; completions * could be issued while we do so. Disconnection may @@ -401,56 +403,6 @@ __acquires(&port->port_lock) return status; } -static void gs_rx_push(unsigned long _port) -{ - struct gs_port *port = (void *)_port; - struct tty_struct *tty = port->port_tty; - - /* With low_latency, tty_flip_buffer_push() doesn't put its - * real work through a workqueue, so the ldisc has a better - * chance to keep up with peak USB data rates. - */ - if (tty) { - tty_flip_buffer_push(tty); - wake_up_interruptible(&tty->read_wait); - } -} - -/* - * gs_recv_packet - * - * Called for each USB packet received. Reads the packet - * header and stuffs the data in the appropriate tty buffer. - * Returns 0 if successful, or a negative error number. - * - * Called during USB completion routine, on interrupt time. - * With port_lock. - */ -static int gs_recv_packet(struct gs_port *port, char *packet, unsigned size) -{ - unsigned len; - struct tty_struct *tty; - - /* I/O completions can continue for a while after close(), until the - * request queue empties. Just discard any data we receive, until - * something reopens this TTY ... as if there were no HW flow control. - */ - tty = port->port_tty; - if (tty == NULL) { - pr_vdebug("%s: ttyGS%d, after close\n", - __func__, port->port_num); - return -EIO; - } - - len = tty_insert_flip_string(tty, packet, size); - if (len > 0) - tasklet_schedule(&port->push); - if (len < size) - pr_debug("%s: ttyGS%d, drop %d bytes\n", - __func__, port->port_num, size - len); - return 0; -} - /* * Context: caller owns port_lock, and port_usb is set */ @@ -469,9 +421,9 @@ __acquires(&port->port_lock) int status; struct tty_struct *tty; - /* no more rx if closed or throttled */ + /* no more rx if closed */ tty = port->port_tty; - if (!tty || test_bit(TTY_THROTTLED, &tty->flags)) + if (!tty) break; req = list_entry(pool->next, struct usb_request, list); @@ -500,36 +452,134 @@ __acquires(&port->port_lock) return started; } -static void gs_read_complete(struct usb_ep *ep, struct usb_request *req) +/* + * RX tasklet takes data out of the RX queue and hands it up to the TTY + * layer until it refuses to take any more data (or is throttled back). + * Then it issues reads for any further data. + * + * If the RX queue becomes full enough that no usb_request is queued, + * the OUT endpoint may begin NAKing as soon as its FIFO fills up. + * 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) { - int status; - struct gs_port *port = ep->driver_data; + struct gs_port *port = (void *)_port; + struct tty_struct *tty; + struct list_head *queue = &port->read_queue; + bool disconnect = false; + bool do_push = false; - spin_lock(&port->port_lock); - list_add(&req->list, &port->read_pool); + /* hand any queued data to the tty */ + spin_lock_irq(&port->port_lock); + tty = port->port_tty; + while (!list_empty(queue)) { + struct usb_request *req; - switch (req->status) { - case 0: - /* normal completion */ - status = gs_recv_packet(port, req->buf, req->actual); - if (status && status != -EIO) - pr_debug("%s: %s %s err %d\n", - __func__, "recv", ep->name, status); - gs_start_rx(port); - break; + req = list_first_entry(queue, struct usb_request, list); - case -ESHUTDOWN: - /* disconnect */ - pr_vdebug("%s: %s shutdown\n", __func__, ep->name); - break; + /* discard data if tty was closed */ + if (!tty) + goto recycle; - default: - /* presumably a transient fault */ - pr_warning("%s: unexpected %s status %d\n", - __func__, ep->name, req->status); - gs_start_rx(port); - break; + /* leave data queued if tty was rx throttled */ + if (test_bit(TTY_THROTTLED, &tty->flags)) + break; + + switch (req->status) { + case -ESHUTDOWN: + disconnect = true; + pr_vdebug(PREFIX "%d: shutdown\n", port->port_num); + break; + + default: + /* presumably a transient fault */ + pr_warning(PREFIX "%d: unexpected RX status %d\n", + port->port_num, req->status); + /* FALLTHROUGH */ + case 0: + /* normal completion */ + break; + } + + /* push data to (open) tty */ + if (req->actual) { + char *packet = req->buf; + unsigned size = req->actual; + unsigned n; + int count; + + /* we may have pushed part of this packet already... */ + n = port->n_read; + if (n) { + packet += n; + size -= n; + } + + count = tty_insert_flip_string(tty, packet, size); + if (count) + do_push = true; + if (count != size) { + /* stop pushing; TTY layer can't handle more */ + port->n_read += count; + pr_vdebug(PREFIX "%d: rx block %d/%d\n", + port->port_num, + count, req->actual); + break; + } + port->n_read = 0; + } +recycle: + list_move(&req->list, &port->read_pool); + } + + /* Push from tty to ldisc; this is immediate with low_latency, and + * may trigger callbacks to this driver ... so drop the spinlock. + */ + if (tty && do_push) { + spin_unlock_irq(&port->port_lock); + tty_flip_buffer_push(tty); + wake_up_interruptible(&tty->read_wait); + spin_lock_irq(&port->port_lock); + + /* tty may have been closed */ + tty = port->port_tty; } + + + /* 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... + * + * REVISIT we should probably add a timer to keep the tasklet + * from starving ... but it's not clear that case ever happens. + */ + if (!list_empty(queue) && tty) { + if (!test_bit(TTY_THROTTLED, &tty->flags)) { + if (do_push) + tasklet_schedule(&port->push); + else + pr_warning(PREFIX "%d: RX not scheduled?\n", + port->port_num); + } + } + + /* If we're still connected, refill the USB RX queue. */ + if (!disconnect && port->port_usb) + gs_start_rx(port); + + spin_unlock_irq(&port->port_lock); +} + +static void gs_read_complete(struct usb_ep *ep, struct usb_request *req) +{ + struct gs_port *port = ep->driver_data; + + /* 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); spin_unlock(&port->port_lock); } @@ -625,6 +675,7 @@ static int gs_start_io(struct gs_port *port) } /* queue read requests */ + port->n_read = 0; started = gs_start_rx(port); /* unblock any pending writes into our circular buffer */ @@ -633,9 +684,10 @@ static int gs_start_io(struct gs_port *port) } else { gs_free_requests(ep, head); gs_free_requests(port->port_usb->in, &port->write_pool); + status = -EIO; } - return started ? 0 : status; + return status; } /*-------------------------------------------------------------------------*/ @@ -809,8 +861,6 @@ static void gs_close(struct tty_struct *tty, struct file *file) else gs_buf_clear(&port->port_write_buf); - tasklet_kill(&port->push); - tty->driver_data = NULL; port->port_tty = NULL; @@ -911,15 +961,17 @@ static void gs_unthrottle(struct tty_struct *tty) { struct gs_port *port = tty->driver_data; unsigned long flags; - unsigned started = 0; spin_lock_irqsave(&port->port_lock, flags); - if (port->port_usb) - started = gs_start_rx(port); + if (port->port_usb) { + /* Kickstart read queue processing. We don't do xon/xoff, + * 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(PREFIX "%d: unthrottle\n", port->port_num); + } spin_unlock_irqrestore(&port->port_lock, flags); - - pr_vdebug("gs_unthrottle: ttyGS%d, %d packets\n", - port->port_num, started); } static const struct tty_operations gs_tty_ops = { @@ -953,6 +1005,7 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding) tasklet_init(&port->push, gs_rx_push, (unsigned long) port); INIT_LIST_HEAD(&port->read_pool); + INIT_LIST_HEAD(&port->read_queue); INIT_LIST_HEAD(&port->write_pool); port->port_num = port_num; @@ -997,7 +1050,7 @@ int __init gserial_setup(struct usb_gadget *g, unsigned count) gs_tty_driver->owner = THIS_MODULE; gs_tty_driver->driver_name = "g_serial"; - gs_tty_driver->name = "ttyGS"; + gs_tty_driver->name = PREFIX; /* uses dynamically assigned dev_t values */ gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL; @@ -1104,6 +1157,8 @@ void gserial_cleanup(void) ports[i].port = NULL; mutex_unlock(&ports[i].lock); + tasklet_kill(&port->push); + /* wait for old opens to finish */ wait_event(port->close_wait, gs_closed(port)); @@ -1241,6 +1296,7 @@ void gserial_disconnect(struct gserial *gser) if (port->open_count == 0 && !port->openclose) gs_buf_free(&port->port_write_buf); gs_free_requests(gser->out, &port->read_pool); + gs_free_requests(gser->out, &port->read_queue); gs_free_requests(gser->in, &port->write_pool); spin_unlock_irqrestore(&port->port_lock, flags); } |