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    SubjectRe: [RESEND/PATCH 5/6] USB: musb-gadget: complete request only if data is transfered over

    On 15-09-2010 10:53, Felipe Balbi wrote:

    >>>> If a DMA interrupt comes when the whole transfer is not yet
    >>>> complete (and
    >>>> other Ming Lei's patches are making this possible),

    >> Oh, here I mixed some other patch with Ming Lei's ones...

    >>>> it will pass due to the

    >>> than this is the actual problem, no ? If we're using mode1 dma (as we
    >>> are on tx path), we should only get dma interrupt when the whole
    >>> transfer has been completed.

    >> The Inventra DMA controller has serious DMA length limitation, so the whole
    >> transfer may take more than one DMA.

    > When I said 'whole transfer' I meant the transfer size you programmed
    > dma to transfer, see that we have (not actual code):

    > if (transfer_size > dma->max_len)
    > transfer_size = dma->max_len;

    > dma->channel_program(...,..., transfer_size,...);

    Ah, I didn't mean the same thing -- I meant the transfer size as specified
    by 'struct usb_request'.

    > with mode1, we will only get irq when dma has transferred transfer_size
    > bytes.


    >>> likewise, this was there before the patch. I don't think the real
    >>> problem lies with this patch, it's been there for a while, don't you
    >>> agree ?

    >> Then what problem this patch fixes, if not this one?

    > if request->length == 1MB and dma->max_len = 128KB, when is_dma is true,
    > request->actual will be different from request->length for 7
    > 'iterations', then only on the 8th it will be the same. I believe that's
    > what Ming is trying to fix.

    I repeat once again: it's too late to check this where Ming is inserting
    the check.

    > Ming, am I correct ?
    >> Let me repeat: in the PIO mode the added check is just duplicate, in the DMA

    > it is duplicate for PIO, but not for DMA.

    I didn't say it was duplicate for DMA, just too late.

    WBR, Sergei

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