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    SubjectRE: [PATCH 3/4] serial: 8250: Add Aspeed UART driver
    Date
    > From: Paul Menzel <pmenzel@molgen.mpg.de>
    > Sent: Friday, February 10, 2023 6:35 PM
    >
    > Dear Chia-Wei,
    >
    >
    > Thank you for your patch.
    >
    > Am 10.02.23 um 08:26 schrieb Chia-Wei Wang:
    > > Add the driver for Aspeed UART/VUART devices, which are 16550A
    > > compatible. It is an wrapper to cover the generic 16550A operation
    >
    > a wrapper
    >
    > > while exetending DMA feature for the devices.
    >
    > extending
    >
    > Is this for all ASPEED devices or only current ones?

    There is major design change of UDMA.
    Therefore, this patch is for AST2600 only.

    >
    > How did you test this? What is the maximum transfer speed?

    Yes.
    I can't remember the precise data. The experiment was done like 2 years ago.
    But it should be above 2MB/s

    >
    > There are other serial drivers also supporting DMA, and those seem to use
    > DMAengine?
    >
    > $ git grep dmaengine drivers/tty/serial/8250/
    >

    Yes.
    The UDMA design is dedicated to, and tightly coupled with each UART/VUART devices.
    And UDMA does not support common DMA control such as suspend/resume.

    We found certain discussions in the old mailing list saying that if a DMA controller is not fully fit into the DMAEngine subsystem,
    placing the implementation in the soc folder might be an option.

    Regards,
    Chiawei
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