On Thu, Jun 10, 2021 at 7:52 AM Horia Geantă <horia.geanta@nxp.com> wrote:
>
> Documentation/core-api/dma-api.rst explicitly allows for partial syncs:
> Synchronise a single contiguous or scatter/gather mapping for the CPU
> and device. With the sync_sg API, all the parameters must be the same
> as those passed into the single mapping API. With the sync_single API,
> you can use dma_handle and size parameters that aren't identical to
> those passed into the single mapping API to do a partial sync.
>
> AFAICS commit 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
> is breaking this functionality.

How about a patch like the attached? Does that fix things for you.

Christoph? Comments - that commit removed the offset calculation
entirely, because the old

        (unsigned long)tlb_addr & (IO_TLB_SIZE - 1)

was wrong, but instead of removing it, I think it should have just
fixed it to be

        (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);

instead. That way the slot offset always matches the slot index calculation.

I also made it then take the offset into account for the alloc_size checks.

Does this UNTESTED patch perhaps do the right thing?

                    Linus