Re: [PARPORT] ECP mode transfers in 2.4.x kernels

From: Tim Waugh (
Date: Mon Sep 10 2001 - 14:39:55 EDT

  • Next message: Philip Blundell: "Re: [PARPORT] ECP mode transfers in 2.4.x kernels"

    On Mon, Sep 10, 2001 at 02:06:39PM -0400, Dave Strauss wrote:

    > I think at least for now I think I'm just going to turn DMA off. I'm
    > still open to trying other experiments, though, if anybody wants to
    > suggest something.

    Looking through the parport DMA code, there is only one thing I can
    see wrong:

                    /* Anyone else waiting for the port? */
                    if (port->waithead) {
                            printk (KERN_DEBUG "Somebody wants the port\n");

                    /* update for possible DMA residue ! */
                    buf -= count;
                    left += count;

    Someone else waiting for the port will screw up our count!

    But this wouldn't cause the problem at hand, I don't think.

    It seems like get_dma_residue(port->dma) == 2 and then -2 on
    successive times round the loop. But that doesn't make sense..

    Do we have enough information to figure out if the problem is inside
    the loop in parport_pc_fifo_write_block_dma rather than between
    successive calls of the function?


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