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    SubjectRe: [PATCH 22/28] sgiseeq: convert from dma_cache_sync to dma_sync_single_for_device
    On Tue, Sep 01, 2020 at 07:38:10PM +0200, Thomas Bogendoerfer wrote:
    > this is the problem:
    >
    > /* Always check for received packets. */
    > sgiseeq_rx(dev, sp, hregs, sregs);
    >
    > so the driver will look at the rx descriptor on every interrupt, so
    > we cache the rx descriptor on the first interrupt and if there was
    > $no rx packet, we will only see it, if cache line gets flushed for
    > some other reason.

    That means a transfer back to device ownership is missing after a
    (negative) check.

    > kick_tx() does a busy loop checking tx descriptors,
    > with just sync_desc_cpu...
    >
    > Thomas.
    >
    > --
    > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
    > good idea. [ RFC1925, 2.3 ]
    ---end quoted text---

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