Re: [Patch] Increase USBFS Bulk Transfer size

Manu Abraham
2011-10-13T05:46:14Z

On Thu, Oct 13, 2011 at 10:29 AM, Markus Rechberger
<mrechberger@gmail.com> wrote:
> On Thu, Oct 13, 2011 at 6:03 AM, Manu Abraham <abraham.manu@gmail.com> wrote:
>> Hello Markus,
>>
>> On Thu, Oct 13, 2011 at 3:39 AM, Markus Rechberger
>> <mrechberger@gmail.com> wrote:
>>> On Wed, Oct 12, 2011 at 11:48 PM, Markus Rechberger
>>> <mrechberger@gmail.com> wrote:
>>>> On Wed, Oct 12, 2011 at 10:33 PM, Greg KH <gregkh@suse.de> wrote:
>>>>> On Wed, Oct 12, 2011 at 06:59:01PM +0200, Markus Rechberger wrote:
>>>>>> On Wed, Oct 12, 2011 at 4:17 PM, Greg KH <gregkh@suse.de> wrote:
>>>>>> > On Wed, Oct 12, 2011 at 02:36:59PM +0200, Markus Rechberger wrote:
>>>>>> >> We have 2 products which can perform better with increased Bulk transfers
>>>>>> >
>>>>>> > I don't believe you :)
>>>>>> >
>>>>>> > As stated before, this patch is not acceptable.  Please work to figure
>>>>>> > out the real reason for your device problems here, this is not the
>>>>>> > correct solution at all.
>>>>>> >
>>>>>>
>>>>>> OK no device support for linux then. Windows and MacOSX are fine.
>>>>>
>>>>> That is your choice, not ours, as you are the one writing the closed
>>>>> source code.  Without usbmon dumps, showing that the problem really is
>>>>> in the kernel code, we can't do anything for you here.
>>>>>
>>>>
>>>>
>>>> here take your usbmon logs:
>>>> http://sundtek.de/support/working.log
>>>> http://sundtek.de/support/notworking.log (this is with your proposed
>>>> split up of 22k).
>>>>
>>>> Isochronous already supports up to 190kb buffers which cause no
>>>> trouble anywhere.
>>>> Bulk is castrated to 15kb buffers and 50kb should be such a big issue
>>>> while applications
>>>> which do not request it are not affected at all.
>>>>
>>>> I'm very angry that you do not really focus on what I write and just
>>>> try to write stories about
>>>> bogus things like my patch might break other applications while I
>>>> pointed out that this is not
>>>> possible with legacy applications which use this interface. It is not
>>>> even possible to read the
>>>> maximum buffer value from the kernelspace.
>>>>
>>>> Your bogus message about 1Gig ram you can put it elsewhere, I checked
>>>> multiple windows drivers
>>>> in the past the buffer size varies between small and something around
>>>> 50k usually.
>>>> I would fully like to avoid to patch this kernel to get those things
>>>> work because I don't want to
>>>> deal with people who just write around the actual issues.
>>>>
>>>> Alsi the fact that bigger buffers are already being used plus the HW
>>>> specifications of our main device also points out to a certain
>>>> buffersize near 50k. But of course you are the smart knowitall without
>>>> the need of explanation why
>>>> those things can be affected by HW and some HW chips have options to
>>>> influence that buffer size.
>>>
>>> And for those who are curious about the logfiles:
>>> Not working one as proposed by Alan that the full buffer size should
>>> be split into 2 requests:
>>>
>>> ffff8800b38d9f00 1231540351 S Bi:2:013:1 -115 12288 <
>>> ffff8800b38d96c0 1231540404 S Bi:2:013:1 -115 11776 <
>>> ffff8800b38d9cc0 1231540440 S Bi:2:013:1 -115 12288 <
>>> ffff880002ede600 1231540496 S Bi:2:013:1 -115 11776 <
>>> ffff8800b38d9f00 1231545491 C Bi:2:013:1 0 12288 = 7a1a0840 1ca8353c
>>> 004b80ec 4de08401 2f0227f8 34005e7e 80181dfd 1a8f700a
>>> ffff88007d51fb40 1231545875 S Bi:2:013:1 -115 12288 <
>>> ffff8800b38d96c0 1231551861 C Bi:2:013:1 0 11776 = 5244e386 a7800000
>>> 010642ea 35bfbba5 373e738b cc035a73 c328a1ff 4da728ce
>>> ffff880002ede0c0 1231556173 S Bi:2:013:1 -115 11776 <
>>> ffff8800b38d9cc0 1231558618 C Bi:2:013:1 0 12288 = db91aae9 2d2532f3
>>> 2e37448a fb36c213 55dda2ad 243122b2 261edb06 875848ac
>>>
>>>
>>> 12288 = 7a1a0840 every Line with 12288 should start with 47 (MPEG-TS Sync byte)
>>>
>>> The working one which allocate 7000 bytes more (oh really big memory
>>> pressure now!)  than this castrated USBFS interface allows.
>>>
>>> ffff88003ac37240 992178919 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37000 992178953 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37c00 992178980 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37e40 992179003 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37240 992190198 C Bi:2:013:1 0 24064 = 471fff10 00000000
>>> 00000000 00000000 00000000 00000000 00000000 00000000
>>> ffff88000601f480 992194368 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37000 992203209 C Bi:2:013:1 0 24064 = 4701b114 43867ee6
>>> 40790660 e898681c 9b1c7dca 08980d43 73181369 9be1bc67
>>> ffff880067e38a80 992204642 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37c00 992216318 C Bi:2:013:1 0 24064 = 4740001c 0000b01d
>>> 0305d500 000000e0 104015e1 504016e1 60401be1 b04022e2
>>> ffff880067e383c0 992219978 S Bi:2:013:1 -115 24064 <
>>> ffff88003ac37e40 992229340 C Bi:2:013:1 0 24064 = 471fff10 00000000
>>> 00000000 00000000 00000000 00000000 00000000 00000000
>>>
>>> everything starts nicely with 0x47
>>
>> Is the transfer size a multiple of 188 bytes in both cases ? In the
>> working case, it looks so, but in the broken case ? Many DTV bridges
>> have fixed DMA apertures and not variable really much, even though the
>> device specifications do state that it might support different block
>> sizes, some modes could be broken. I guess most likely, you would have
>> handled this situation.
>>
>> Other issues that could possibly happen (wrt your jitter) is a high
>> latency (in the particular case of failures) where the received data
>> have unusable relative timestamps wrt DTS and or PTS.
>>
>> The only areas where you can have a corrupted stream as you mentioned
>> "jitter" is either lost frames or the above two cases. I don't know
>> what's the issue in your case, but might help to track down the issue
>> altogether.
>>
>
> I am not so sure about that one but I guess that's it.
> The 'black outs (0xff after the Sync byte)' are also related to the
> demodulator (not perfect signal, it's still DVB-T) but
> the alignment is just perfect
> I also guess the misaligning problem could be related to the latency
> and that the bridges have some
> fixed or adjustable bulk transfer settings to work with that. In the
> end the additional features
> are done with software demodulation so there will be a certain minimal
> system requirement anyway.
>

I guess you meant to imply "software decoding" of the MPEG stream I
would say, rather than "demodulation" of the Baseband signal.

> What would be against that theory would be that 2*that maximum
> transfer size also results in a misaligned
> video. Since I tried many other transfer sizes before I've been told
> to use that one and I even thought the
> device is broke but it just works that way... also with Windows and MacOSX.
> As far as I can tell for user experience the device is okay with 24064 bytes.
>
> TV has been running for several days now with no issues (I was also
> testing the ts 'blackouts' where data
> after the sync byte 0x47 is 0xff on weak signal, the TS sync byte
> itself is still valid)

I have had such an issue earlier (0x47 followed 0xff. ie 0x47 0x1f 0xf
0x00 0x00 0x00 and so on) with a stream from the demodulator on a PCIe
device, but eventually it turned out to be that, it was handling the
device DMA in the reverse order, the device having 8 DMA apertures of
which all 8 had to be used for stream transfer.

RING(W) : Buf:2 Tail: 2 Count:0 Size:16
RING(R): Buf:2 Head: 2 Count:! Size: 16
47 If ff 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Additionally, to be noted is that the ISO13818-1 specification allows
NULL padding of the TS by the channel modulator to achieve a CBR, from
VBR ES's. There exists an ETSI specification dealing with NULL padding
explicitly, don't remember the exact TR no.

After a search, EN 302755 v1.1.1 Section 5.1.5 deals with that, A
quick glance at least wrt to T2, I remember the same while I was
working with S2 as well.

All such issues mixed when together can be very nasty and painful,
making things difficult.

Regards,
Manu