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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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