usb: dwc2: masquerade split-interrupt transfers #6936
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Masquerading Interrupt split transfers as Control puts the transfer into the non-periodic handler in the hub. This stops the hub dropping complete-split data in the microframe after a CSPLIT should have arrived, improving resilience to host IRQ latency. Devices are none the wiser - the handshake tokens are the same. Originally devised by Hans Petter Selasky @ FreeBSD. (v2: dwc2 needs an un-masquerade prior to channel interrupt handling) Signed-off-by: Jonathan Bell <[email protected]>
Control Setup phase transfers needs an 8 byte maxpacket override, or drivers doing a GET with a small buffer as a split transaction would cause broken transfers. Signed-off-by: Jonathan Bell <[email protected]>
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Second attempt at porting the dwc_otg hack to avoid dropped split transactions.
Transactions now "look OK" on the bus analyser but this needs more soak testing with different hub implementations.