From 314b3e0881c6acb4f40e07565ac1a7798c7698a3 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Tue, 26 Oct 2010 05:15:46 -0300 Subject: [PATCH] [media] gspca: submit interrupt urbs *after* isoc urbs Currently gspca supported usb-1.1 webcams for which we support the input button through an interrupt endpoint won't stream (not enough bandwidth error) when used through an USB-2.0 hub. After much debugging I've found out that the cause for this is that the ehci-sched.c schedeling code does not like it when there are already urb's scheduled when (large) isoc urbs are queued. By moving the submission of the interrupt urbs to after submitting the isoc urbs the camera starts working again through usb-2.0 hubs. Note that this does not fix isoc. streaming through a usb-hub while another 1.1 usb device (like the microphone of the same cam) is also active at the same time :( I've spend a long time analyzing the linux kernel ehci scheduler code, resulting in this (long) mail: http://www.spinics.net/lists/linux-usb/msg37982.html The conclusion of the following mail thread is that yes there are several issues when using usb-1.1 devices through a usb-2.0 hub, but these are not easily fixable in the current code. Fixing this in ehci-sched.c requires an almost full rewrite, which is not bound to happen anytime soon. So with this patch gspca driven usb-1.1 webcams will atleast work when connected through an usb-2.0 hub when the microphone is not used. As an added bonus this patch avoids extra destroy/create input urb cycles when we end up falling back to a lower speed alt setting because of bandwidth limitations. Signed-off-by: Hans de Goede Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/gspca/gspca.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/media/video/gspca/gspca.c b/drivers/media/video/gspca/gspca.c index 8fe8fb486d62..dbd63c542317 100644 --- a/drivers/media/video/gspca/gspca.c +++ b/drivers/media/video/gspca/gspca.c @@ -676,13 +676,11 @@ static struct usb_host_endpoint *get_ep(struct gspca_dev *gspca_dev) i, ep->desc.bEndpointAddress); gspca_dev->alt = i; /* memorize the current alt setting */ if (gspca_dev->nbalt > 1) { - gspca_input_destroy_urb(gspca_dev); ret = usb_set_interface(gspca_dev->dev, gspca_dev->iface, i); if (ret < 0) { err("set alt %d err %d", i, ret); ep = NULL; } - gspca_input_create_urb(gspca_dev); } return ep; } @@ -781,7 +779,7 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev) if (!gspca_dev->present) { ret = -ENODEV; - goto out; + goto unlock; } /* reset the streaming variables */ @@ -802,8 +800,10 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev) if (gspca_dev->sd_desc->isoc_init) { ret = gspca_dev->sd_desc->isoc_init(gspca_dev); if (ret < 0) - goto out; + goto unlock; } + + gspca_input_destroy_urb(gspca_dev); ep = get_ep(gspca_dev); if (ep == NULL) { ret = -EIO; @@ -873,6 +873,8 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev) } } out: + gspca_input_create_urb(gspca_dev); +unlock: mutex_unlock(&gspca_dev->usb_lock); return ret; } -- 2.20.1