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    SubjectRe: [PATCH] net: fs_enet: sync rx dma buffer before reading
    On Sat, 21 May 2022 06:44:41 +0000 Christophe Leroy wrote:
    > > Hm, I think the patch is necessary, sorry if you're also saying that
    > > and I'm misinterpreting.
    >
    > Well, I say the contrary.
    >
    > On the mainline the patch may be applied as is, it won't harm.
    >
    > However, it is gets applied to kernel 4.9 (based on the fixes: tag), it
    > will break the driver for at least powerpc 8xx.

    I see, we should make a note of that in the commit message so it doesn't
    get sucked into stable.

    > > Without the dma_sync_single_for_cpu() if swiotlb is used the data
    > > will not be copied back into the original buffer if there is no sync.
    >
    > I don't know how SWIOTLB works or even what it is, does any of the
    > microcontrollers embedding freescale ethernet uses that at all ?

    AFAIU SWIOTLB basically forces the use of bounce buffers even if the
    device can reach the entire DRAM. I think some people also use it for
    added security? IDK. I mostly use it to check if I'm using the DMA API
    "right" :)

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