Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932490Ab1FVQDv (ORCPT ); Wed, 22 Jun 2011 12:03:51 -0400 Received: from mail.mnsspb.ru ([84.204.75.2]:40584 "EHLO mail.mnsspb.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932471Ab1FVQDs (ORCPT ); Wed, 22 Jun 2011 12:03:48 -0400 From: Kirill Smelkov To: linux-usb@vger.kernel.org Cc: Greg Kroah-Hartman , linux-uvc-devel@lists.berlios.de, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Kirill Smelkov , Alan Stern Subject: [RFC, PATCH] USB: EHCI: Allow users to override 80% max periodic bandwidth Date: Wed, 22 Jun 2011 20:02:47 +0400 Message-Id: <1308758567-8205-1-git-send-email-kirr@mns.spb.ru> X-Mailer: git-send-email 1.7.6.rc1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5040 Lines: 144 There are cases, when 80% max isochronous bandwidth is too limiting. For example I have two USB video capture cards which stream uncompressed video, and to stream full NTSC + PAL videos we'd need NTSC 640x480 YUV422 @30fps ~17.6 MB/s PAL 720x576 YUV422 @25fps ~19.7 MB/s isoc bandwidth. Now, due to limited alt settings in capture devices NTSC one ends up streaming with max_pkt_size=2688 and PAL with max_pkt_size=2892, both with interval=1. In terms of microframe time allocation this gives NTSC ~53us PAL ~57us and together ~110us > 100us == 80% of 125us uframe time. So those two devices can't work together simultaneously because the'd over allocate isochronous bandwidth. 80% seemed a bit arbitrary to me, and I've tried to raise it to 90% and both devices started to work together, so I though sometimes it would be a good idea for users to override hardcoded default of max 80% isoc bandwidth. After all, isn't it a user who should decide how to load the bus? If I can live with 10% or even 5% bulk bandwidth that should be ok. I'm a USB newcomer, but that 80% seems to be chosen pretty arbitrary to me, just to serve as a reasonable default. NOTE: for two streams with max_pkt_size=3072 (worst case) both time allocation would be 60us+60us=120us which is 96% periodic bandwidth leaving 4% for bulk and control. I think this should work too. Signed-off-by: Kirill Smelkov Cc: Alan Stern --- drivers/usb/host/ehci-hcd.c | 16 ++++++++++++++++ drivers/usb/host/ehci-sched.c | 17 +++++++---------- 2 files changed, 23 insertions(+), 10 deletions(-) diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index c606b02..1d36e72 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -112,6 +112,14 @@ static unsigned int hird; module_param(hird, int, S_IRUGO); MODULE_PARM_DESC(hird, "host initiated resume duration, +1 for each 75us\n"); +/* + * max periodic time per microframe + * (be careful, USB 2.0 requires it to be 100us = 80% of 125us) + */ +static unsigned int uframe_periodic_max = 100; +module_param(uframe_periodic_max, uint, S_IRUGO); +MODULE_PARM_DESC(uframe_periodic_max, "maximum allowed periodic part of a microframe, us"); + #define INTR_MASK (STS_IAA | STS_FATAL | STS_PCD | STS_ERR | STS_INT) /*-------------------------------------------------------------------------*/ @@ -571,6 +579,14 @@ static int ehci_init(struct usb_hcd *hcd) hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params); /* + * tell user, if using non-standard (80% == 100 usec/uframe) bandwidth + */ + if (uframe_periodic_max != 100) + ehci_info(ehci, "using non-standard max periodic bandwith " + "(%u%% == %u usec/uframe)", + 100*uframe_periodic_max/125, uframe_periodic_max); + + /* * hw default: 1K periodic list heads, one per frame. * periodic_size can shrink by USBCMD update if hcc_params allows. */ diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c index d12426f..fb374f2 100644 --- a/drivers/usb/host/ehci-sched.c +++ b/drivers/usb/host/ehci-sched.c @@ -172,7 +172,7 @@ periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe) } } #ifdef DEBUG - if (usecs > 100) + if (usecs > uframe_periodic_max) ehci_err (ehci, "uframe %d sched overrun: %d usecs\n", frame * 8 + uframe, usecs); #endif @@ -709,11 +709,8 @@ static int check_period ( if (uframe >= 8) return 0; - /* - * 80% periodic == 100 usec/uframe available - * convert "usecs we need" to "max already claimed" - */ - usecs = 100 - usecs; + /* convert "usecs we need" to "max already claimed" */ + usecs = uframe_periodic_max - usecs; /* we "know" 2 and 4 uframe intervals were rejected; so * for period 0, check _every_ microframe in the schedule. @@ -1286,9 +1283,9 @@ itd_slot_ok ( { uframe %= period; do { - /* can't commit more than 80% periodic == 100 usec */ + /* can't commit more than uframe_periodic_max usec */ if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7) - > (100 - usecs)) + > (uframe_periodic_max - usecs)) return 0; /* we know urb->interval is 2^N uframes */ @@ -1345,7 +1342,7 @@ sitd_slot_ok ( #endif /* check starts (OUT uses more than one) */ - max_used = 100 - stream->usecs; + max_used = uframe_periodic_max - stream->usecs; for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) { if (periodic_usecs (ehci, frame, uf) > max_used) return 0; @@ -1354,7 +1351,7 @@ sitd_slot_ok ( /* for IN, check CSPLIT */ if (stream->c_usecs) { uf = uframe & 7; - max_used = 100 - stream->c_usecs; + max_used = uframe_periodic_max - stream->c_usecs; do { tmp = 1 << uf; tmp <<= 8; -- 1.7.6.rc1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/