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 <[email protected]>
Cc: Alan Stern <[email protected]>
---
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
On 20:02 Wed 22 Jun , Kirill Smelkov wrote:
> 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.
There is nothing arbitrary about 80%. The USB 2.0 Specification constrains
periodic transfers for high-speed endpoints to 80% of the microframe. See
section 5.6.4.
-mfm
> 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 <[email protected]>
> Cc: Alan Stern <[email protected]>
> ---
> 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 [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
On 10:30 Wed 22 Jun , matt mooney wrote:
> On 20:02 Wed 22 Jun , Kirill Smelkov wrote:
> > 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.
>
> There is nothing arbitrary about 80%. The USB 2.0 Specification constrains
> periodic transfers for high-speed endpoints to 80% of the microframe. See
> section 5.6.4.
>
Looking at the patch, I see that you probably already knew that.
So I digress and defer to the USB experts ;)
-mfm
> > 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 <[email protected]>
> > Cc: Alan Stern <[email protected]>
> > ---
> > 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 [email protected]
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
On Wed, 22 Jun 2011, Kirill Smelkov wrote:
> 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.
This seems like the sort of feature somebody might reasonably want to
use -- if they know exactly what they're doing.
> 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.
At 480 Mb/s, each microframe holds 7500 bytes (less if you count
bit-stuffing). 4% of that is 300 bytes, which is not enough for a
512-byte bulk packet. I think you'd run into trouble trying to do any
serious bulk transfers on such a tight schedule.
> Signed-off-by: Kirill Smelkov <[email protected]>
> Cc: Alan Stern <[email protected]>
> ---
> 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");
> +
This probably should be a sysfs attribute rather than a module
parameter, so that it can be applied to individual buses separately.
> #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);
> +
> + /*
Check for invalid values. This should never be less than 100 or
greater than 125.
> * 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)
These changes all seem right.
Alan Stern
On Wed, Jun 22, 2011 at 03:22:28PM -0400, Alan Stern wrote:
> On Wed, 22 Jun 2011, Kirill Smelkov wrote:
>
> > 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.
>
> This seems like the sort of feature somebody might reasonably want to
> use -- if they know exactly what they're doing.
Yes, thanks, exactly my case. Now I know the idea won't be rejected it
can be polished.
> > 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.
>
> At 480 Mb/s, each microframe holds 7500 bytes (less if you count
> bit-stuffing). 4% of that is 300 bytes, which is not enough for a
> 512-byte bulk packet. I think you'd run into trouble trying to do any
> serious bulk transfers on such a tight schedule.
Yes, you seem to be right.
I still think 4% is maybe enough for control traffic.
> > Signed-off-by: Kirill Smelkov <[email protected]>
> > Cc: Alan Stern <[email protected]>
> > ---
> > 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");
> > +
>
> This probably should be a sysfs attribute rather than a module
> parameter, so that it can be applied to individual buses separately.
Agree
> > #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);
> > +
> > + /*
>
> Check for invalid values. This should never be less than 100 or
> greater than 125.
Ok. By the way, why should we limit it to be not less than 100?
Likewise, a user who knows exactly what he/she is doing could limit
periodic bandwidth to be less than 80% required by USB specification.
> > * 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)
>
> These changes all seem right.
Thanks. I'll try to prepare updated patch.
Kirill
On Wed, Jun 22, 2011 at 10:35:44AM -0700, matt mooney wrote:
> On 10:30 Wed 22 Jun , matt mooney wrote:
> > On 20:02 Wed 22 Jun , Kirill Smelkov wrote:
> > > 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.
> >
> > There is nothing arbitrary about 80%. The USB 2.0 Specification constrains
> > periodic transfers for high-speed endpoints to 80% of the microframe. See
> > section 5.6.4.
> >
>
> Looking at the patch, I see that you probably already knew that.
>
> So I digress and defer to the USB experts ;)
Yes, it was meant as 80% being arbitrary chosen by USB 2.0
specification. Notes taken - I'll clarify patch description.
Thanks for commenting,
Kirill
On Thu, 23 Jun 2011, Kirill Smelkov wrote:
> > At 480 Mb/s, each microframe holds 7500 bytes (less if you count
> > bit-stuffing). 4% of that is 300 bytes, which is not enough for a
> > 512-byte bulk packet. I think you'd run into trouble trying to do any
> > serious bulk transfers on such a tight schedule.
>
> Yes, you seem to be right.
>
> I still think 4% is maybe enough for control traffic.
It should be.
> > > @@ -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);
> > > +
> > > + /*
> >
> > Check for invalid values. This should never be less than 100 or
> > greater than 125.
>
> Ok. By the way, why should we limit it to be not less than 100?
> Likewise, a user who knows exactly what he/she is doing could limit
> periodic bandwidth to be less than 80% required by USB specification.
What's the point? If you want to use less than 80% of your bandwidth
for periodic transfers, go ahead and do so. You don't need to change
the limit.
Alan Stern
On Thu, Jun 23, 2011 at 01:14:04PM -0400, Alan Stern wrote:
> On Thu, 23 Jun 2011, Kirill Smelkov wrote:
>
> > > At 480 Mb/s, each microframe holds 7500 bytes (less if you count
> > > bit-stuffing). 4% of that is 300 bytes, which is not enough for a
> > > 512-byte bulk packet. I think you'd run into trouble trying to do any
> > > serious bulk transfers on such a tight schedule.
> >
> > Yes, you seem to be right.
> >
> > I still think 4% is maybe enough for control traffic.
>
> It should be.
Ok then.
At least devices could be start/stopped, and frankly if someone loads
the bus with two high-bandwidth isoc streams, there is no reason to
expect any bulk transfer to happen at all.
> > > > @@ -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);
> > > > +
> > > > + /*
> > >
> > > Check for invalid values. This should never be less than 100 or
> > > greater than 125.
> >
> > Ok. By the way, why should we limit it to be not less than 100?
> > Likewise, a user who knows exactly what he/she is doing could limit
> > periodic bandwidth to be less than 80% required by USB specification.
>
> What's the point? If you want to use less than 80% of your bandwidth
> for periodic transfers, go ahead and do so. You don't need to change
> the limit.
I though it would be good for generality -- i.e. if someone wants to
limit maximum isoc bandwidth to say 50% so that would never be
overallocated by that limit that would be handy.
But I agree - it's a bit artificial, so in updated patch I've left what
you originally suggested to be 100 <= uframe_periodic_max < 125 (ommitting =125).
Thanks,
Kirill