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    Subject[PATCH 72/71] ncr5380: Fix pseudo-DMA
    Date
    Pseudo-DMA (PDMA) has been broken for ages, resulting in hangs on
    53C400-based cards.

    According to 53C400 datasheet, PDMA transfer length must be a multiple
    of 128. Check if that's true and use PIO if it's not.

    This makes PDMA work on 53C400 (Canon FG2-5202).

    Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
    ---
    drivers/scsi/g_NCR5380.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
    index 0daffe2..a9a237f 100644
    --- a/drivers/scsi/g_NCR5380.c
    +++ b/drivers/scsi/g_NCR5380.c
    @@ -703,6 +703,10 @@ static int generic_NCR5380_dma_xfer_len(struct scsi_cmnd *cmd)
    !(cmd->SCp.this_residual % transfersize))
    transfersize = 32 * 1024;

    + /* 53C400 datasheet: non-modulo-128-byte transfers should use PIO */
    + if (transfersize % 128)
    + transfersize = 0;
    +
    return transfersize;
    }

    --
    Ondrej Zary


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