第二十六篇:USB3.0高带宽ISO(48KBytes/125us)实战

USB3.1技术已经推出, 10Gbps的速率足以满足数据, HD视频传输的要求.

要步入USB3.1的研发, 还得将USB3.0的基础打扎实.

微软提供的SUPER MUTT仅仅包括一个接口0, 其下有两个ALT, ALT 1与ALT 2, 分别包括了两对ISO IN/OUT端点, 只是, 仅仅有ALT 2下的ISO OUT EP的bMaxBurst为1,
而其他三个ISO EP的bMaxBurst均为0, 而全部的ISO EP的Mult均为0.

即仅仅有一个ISO EP支持2KBytes/125us的能力, 其余三个ISO EP仅仅支持1KBytes/125us的能力, 技术上来讲,
远远未达到高带宽(48KBytes/125us)的上限.

这种设备,甚至都不如一个高带宽的USB2.0的设备(3KBytes/125us),用来衡量系统中USB3.0
xHCI HOST的高带宽能力也就无从谈起了.

于是, 利用自开发的USB3.0 silicon, 对设备端驱动稍作改动, 经过Lecory
Advisor T3 USB3.0分析仪的验证, 证明设备端的ISO EP具有接收与发送48KBytes/125us的能力.

接下来, 则须要用该设备来验证xHCI USB3.0 HOST的ISO高带宽能力.

測试平台为INTEL xHCI USB3.0 HOST, Win8 USB3 STACK.

先给出測试结果:

(1.1) HOST发送48*8KBYTES的数据

ISO MaxPacketSize = 49152

000000830.01842206read-write
irp failed with status C0000001

000000850.01842534urb
header status C0000B00
00000089 0.01843355IsoPacket[0].offset = 0           IsoPacket[0].Length = 49152 IsoPacket[0].Status = c0030000
00000091 0.01843889IsoPacket[1].offset = 49152   IsoPacket[1].Length = 49152 IsoPacket[1].Status = c0030000
00000093 0.01844382IsoPacket[2].offset = 98304   IsoPacket[2].Length = 49152 IsoPacket[2].Status = c0030000
00000095 0.01844915IsoPacket[3].offset = 147456 IsoPacket[3].Length = 49152 IsoPacket[3].Status = c0030000
00000097 0.01846065IsoPacket[4].offset = 196608 IsoPacket[4].Length = 49152 IsoPacket[4].Status = c0030000
00000099 0.01846393IsoPacket[5].offset = 245760 IsoPacket[5].Length = 49152 IsoPacket[5].Status = c0030000
00000101 0.01846763IsoPacket[6].offset = 294912 IsoPacket[6].Length = 49152 IsoPacket[6].Status = c0030000
00000103 0.01847091IsoPacket[7].offset = 344064 IsoPacket[7].Length = 49152 IsoPacket[7].Status = c0030000

Total data transferred = 0(dec), 0(hex)

(1.2)  HOST接收48*8KBYTES的数据

000001690.02440798IsoPacket[0].offset
= 0           IsoPacket[0].Length = 49152     IsoPacket[0].Status = 0
00000171 0.02441290IsoPacket[1].offset = 49152   IsoPacket[1].Length = 49152     IsoPacket[1].Status = 0
00000173 0.02441824IsoPacket[2].offset = 98304   IsoPacket[2].Length = 0             IsoPacket[2].Status = c0030000
00000175 0.02442317IsoPacket[3].offset = 147456 IsoPacket[3].Length = 0             IsoPacket[3].Status = c0030000
00000177 0.02442850IsoPacket[4].offset = 196608 IsoPacket[4].Length = 49152     IsoPacket[4].Status = c0030000
00000179 0.02443343IsoPacket[5].offset = 245760 IsoPacket[5].Length = 0             IsoPacket[5].Status = c0030000
00000181 0.02444533IsoPacket[6].offset = 294912 IsoPacket[6].Length = 0             IsoPacket[6].Status = c0030000
00000183 0.02444821IsoPacket[7].offset = 344064 IsoPacket[7].Length = 49152     IsoPacket[7].Status = 0

这里比較有意思的是:

8个包中, 有三个(0, 1, 7)是成功传输了48K的, 另一个尽管也传输了48K, 但系统USB3.0 STACK觉得该ISO PACKET(4)是不成功的.

这个不成功的原因, 后文中会解释原因.

我所说的有意思是, USB3 STACK在填UrbIsochronousTransfer.TransferBufferLength的时候, 却是4*48K, 而不是3*48K.

从以上USB分析仪中的数据能够发现, 这8次写失败的原因有两个:

1. xHCI HOST没有在一个UFRAME中将数据发完,

2. XHCI HOST根本没有发数据, 甚至都没有在这个UFRAME中发出PING

归结起来, 就是系统USB SUBSYSTEM, 甚至包括MEMORY CONTROLLER, 系统总线等一系列的因素所导致.

对于读成功的情况, 则是在一个UFRAME中, XHCI HOST引发了(32+16)个1K的包的读.

对于不成功的情况, 则是UFRAME中, XHCI HOST没有发出ACK IN来读取设备端的数据, 也甚至连PING都没有发出.

(2.1) 48K*1写:

00000082
0.00891627 read-write irp failed with status C0000001
00000084 0.00891914
urb header status C0000B00
00000088 0.00892735
IsoPacket[0].offset = 0           IsoPacket[0].Length = 49152 IsoPacket[0].Status = c0030000
00000090 0.00893269
IsoPacket[1].offset = 49152   IsoPacket[1].Length = 0         IsoPacket[1].Status = c0020000
00000092 0.00893803
IsoPacket[2].offset = 98304   IsoPacket[2].Length = 0         IsoPacket[2].Status = c0020000
00000094 0.00894295
IsoPacket[3].offset = 147456 IsoPacket[3].Length = 0         IsoPacket[3].Status = c0020000 
00000096 0.00895527
IsoPacket[4].offset = 196608 IsoPacket[4].Length = 0         IsoPacket[4].Status = c0020000
00000098 0.00895855
IsoPacket[5].offset = 245760 IsoPacket[5].Length = 0         IsoPacket[5].Status = c0020000
00000100 0.00896184
IsoPacket[6].offset = 294912 IsoPacket[6].Length = 0         IsoPacket[6].Status = c0020000
00000102 0.00896471
IsoPacket[7].offset = 344064 IsoPacket[7].Length = 0         IsoPacket[7].Status = c0020000
00000110 0.00897498
Total data transferred = 0(dec), 0(hex)

当中, 写没成功, 原因与48*8K同样, 没有在一个UFRAME将数据发完.

后面的ERROR CODE c0020000并不是真正的错误, 而是上层没有数据可发导致.

(2.2)48K*1读:

00000168
0.01482911 IsoPacket[0].offset = 0           IsoPacket[0].Length = 49152   IsoPacket[0].Status = 0
00000170 0.01483404
IsoPacket[1].offset = 49152   IsoPacket[1].Length = 0           IsoPacket[1].Status = c0030000
00000172 0.01483938
IsoPacket[2].offset = 98304   IsoPacket[2].Length = 0           IsoPacket[2].Status = c0030000
00000174 0.01484389
IsoPacket[3].offset = 147456 IsoPacket[3].Length = 49152   IsoPacket[3].Status = 0
00000176 0.01485498
IsoPacket[4].offset = 196608 IsoPacket[4].Length = 0           IsoPacket[4].Status = c0030000
00000178 0.01485826
IsoPacket[5].offset = 245760 IsoPacket[5].Length = 0           IsoPacket[5].Status = c0030000
00000182 0.01486196
IsoPacket[6].offset = 294912 IsoPacket[6].Length = 49152   IsoPacket[6].Status = 0
00000186 0.01486524
IsoPacket[7].offset = 344064 IsoPacket[7].Length = 0           IsoPacket[7].Status = c0030000

情况和48K*8情况同样.

仅仅是这里没有出现既传输了数据, 又是出错的情况.

(3.1) 32K*8 WRITE

(3.2) 32K*8 READ

都成功.

总结:

INTEL的xHCI系统加上WIN8的USB3 STACK能够达到32KB/UFRAME的能力, 但不能达到48KB/UFRAME的能力.