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Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller

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  Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller Mathias Nyman <mathias.nyman@intel.com> - 2015-10-19 13:30 +0200
    Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller chunfeng yun <chunfeng.yun@mediatek.com> - 2015-10-20 08:40 +0200
      Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller Mathias Nyman <mathias.nyman@intel.com> - 2015-10-20 10:30 +0200

#1250573 — Re: [PATCH v9 4/5] xhci: mediatek: support MTK xHCI host controller

>>
>> So basically we are trying to use as many microframes as possible with as few packets
>> per microframe as possible.
>>
>> Did I understand this correctly?
> Yes, you are right.
>
>> How will devices react if they expect to get 16 packets every 16th microframe,
>> but they get one packet every microframe instead?
> I think that the synchronous endpoint must specify its period by
> bInterval, but can't specify how data should be transfered during the
> period by the host, and it just only receives data passively. So the
> device can receive data correctly in the case(bInterval is 5).
>
> quote from usb3_r1.0 section4.4.8 Isochronous Transfers:
> "The host can request data from the device or send data to the device at
> any time during the service interval for a particular endpoint on that
> device"
>

As I understand the 4.4.8 section it just means the device can't assume a fixed
time interval between transfers, meaning that the host can use the last microframe
in one esit and the first microframe in the next esit, but still only use 1 microframe
per esit.

Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split
to 1 burst of 11 packets, 2 burst (8 + 3),  3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or
11 bursts of 1. These are however all within the same microframe. Splitting the
transfer into several microframes in a esit kind of makes the whole interval concept pointless.

-Mathias



  

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#1251308

hi,
On Mon, 2015-10-19 at 14:25 +0300, Mathias Nyman wrote:
> >>
> >> So basically we are trying to use as many microframes as possible with as few packets
> >> per microframe as possible.
> >>
> >> Did I understand this correctly?
> > Yes, you are right.
> >
> >> How will devices react if they expect to get 16 packets every 16th microframe,
> >> but they get one packet every microframe instead?
> > I think that the synchronous endpoint must specify its period by
> > bInterval, but can't specify how data should be transfered during the
> > period by the host, and it just only receives data passively. So the
> > device can receive data correctly in the case(bInterval is 5).
> >
> > quote from usb3_r1.0 section4.4.8 Isochronous Transfers:
> > "The host can request data from the device or send data to the device at
> > any time during the service interval for a particular endpoint on that
> > device"
> >
> 
> As I understand the 4.4.8 section it just means the device can't assume a fixed
> time interval between transfers, meaning that the host can use the last microframe
> in one esit and the first microframe in the next esit, but still only use 1 microframe
> per esit.
> 
> Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split
> to 1 burst of 11 packets, 2 burst (8 + 3),  3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or
> 11 bursts of 1. These are however all within the same microframe. Splitting the
> transfer into several microframes in a esit kind of makes the whole interval concept pointless.
> 
It doesn't say that the packets should be transfered within the same
microframe (bus interval), as I understand it means service interval;

The direct prove resides in figure 8-56/8-57.

Term: 
1. BI, bus interval, a 125 us period that establishes the internal
boundary of service interval, aka uframe;
2. SSI, Support Smart Isochronous;
3. DBI, Data in this Bus Interval is done;
4. NBI, Numbers of Bus Interval;

As the figure shows, the service interval = 8 BI, that host distribute 2
packets @1st uframe, keep U1/U2 state for the next 3uframe, then
transmit 4 packets @4th uframe, and the remaining 3 packet in the last
frame.

Please notice that this just is an example illustrated by spec, but we
can derive the conclusion that the distribution of packet in a service
interval is completely decided by host, and can split isoc transfers
across multiple uframes.

PS: as you can see, MTK implementation of schedule algorithms is an
implementation of Smart Isochronous of which the smart side resides in
software.


> -Mathias
> 
> 
> 
>   
> 


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#1251429

On 20.10.2015 09:29, chunfeng yun wrote:
> hi,
> On Mon, 2015-10-19 at 14:25 +0300, Mathias Nyman wrote:
>>>>
>>>> So basically we are trying to use as many microframes as possible with as few packets
>>>> per microframe as possible.
>>>>
>>>> Did I understand this correctly?
>>> Yes, you are right.
>>>
>>>> How will devices react if they expect to get 16 packets every 16th microframe,
>>>> but they get one packet every microframe instead?
>>> I think that the synchronous endpoint must specify its period by
>>> bInterval, but can't specify how data should be transfered during the
>>> period by the host, and it just only receives data passively. So the
>>> device can receive data correctly in the case(bInterval is 5).
>>>
>>> quote from usb3_r1.0 section4.4.8 Isochronous Transfers:
>>> "The host can request data from the device or send data to the device at
>>> any time during the service interval for a particular endpoint on that
>>> device"
>>>
>>
>> As I understand the 4.4.8 section it just means the device can't assume a fixed
>> time interval between transfers, meaning that the host can use the last microframe
>> in one esit and the first microframe in the next esit, but still only use 1 microframe
>> per esit.
>>
>> Section 8.12.6.1 describes how a 11 packet isoc transfer is allowed to be split
>> to 1 burst of 11 packets, 2 burst (8 + 3),  3 burst (4+4+3) 6 bursts (2+2+2+2+2+1) or
>> 11 bursts of 1. These are however all within the same microframe. Splitting the
>> transfer into several microframes in a esit kind of makes the whole interval concept pointless.
>>
> It doesn't say that the packets should be transfered within the same
> microframe (bus interval), as I understand it means service interval;
>
> The direct prove resides in figure 8-56/8-57.
>
> Term:
> 1. BI, bus interval, a 125 us period that establishes the internal
> boundary of service interval, aka uframe;
> 2. SSI, Support Smart Isochronous;
> 3. DBI, Data in this Bus Interval is done;
> 4. NBI, Numbers of Bus Interval;
>
> As the figure shows, the service interval = 8 BI, that host distribute 2
> packets @1st uframe, keep U1/U2 state for the next 3uframe, then
> transmit 4 packets @4th uframe, and the remaining 3 packet in the last
> frame.
>
> Please notice that this just is an example illustrated by spec, but we
> can derive the conclusion that the distribution of packet in a service
> interval is completely decided by host, and can split isoc transfers
> across multiple uframes.

So it seems. You're right

>
> PS: as you can see, MTK implementation of schedule algorithms is an
> implementation of Smart Isochronous of which the smart side resides in
> software.

Thanks for the clarification, I now understand how the implementation works

-Mathias  

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