Re: [PATCH] musb: fix ISOC Tx programming for CPPI DMAs

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Gupta, Ajay Kumar wrote:

>>>>This part is being done at musb_host_rx()

>>>   You're doing it in musb_host_tx() actually. Although musb_host_rx()
>>>is also broken WRT the isochronous transfers.

>>>> doing next packet programming within same urb and *not* starting next

>>>urb. Thus musb_start_urb() doesn't come into this path.

>>>   What? Read the code, please -- musb_start_urb() call should always
>>>precede musb_host_tx() which handles the DMA interrupt. Unless something
>>>clears DMAReqEnab after musb_start_urb() call, setting it only once
>>>should work.

>>musb_start_urb() call does precede musb_host_tx() but when urb is
>>*completed*.

> I think you are aware that there are multiple packets within same isochronous urb and musb_start_urb() programs only for first packet.
> 
> ============================================================
>         case USB_ENDPOINT_XFER_ISOC:
>                 qh->iso_idx = 0;
>                 qh->frame = 0;
>                 offset = urb->iso_frame_desc[0].offset;
>                 len = urb->iso_frame_desc[0].length;
> ============================================================

    Sure. What I'm still not aware of is where and how the TXCSR DMA bits 
are cleared after the first fragment. Hopefully, testing will reveal this...

WBR, Sergei