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    SubjectRe: [PATCH] ide-dma.c, ide.c, ide.h, kernel 2.4.24

    > Glenn, your patch hides potential problems - these functions shouldn't be
    > called if host doesn't support DMA. However there is one place when
    > ->ide_dma_host_off() shouldn't be called unconditionally, here is a patch.
    > It is not pretty but at least consistent - we check hwif->ide_dma_check
    > to see if DMA is supported in other places too. Does it fix the problem?

    Not quite. If we go forward with a patch like that, then it must be
    updated to include at least two other places that I know of
    immediately. The updated patch would be something similar to the one
    at the bottom of this e-mail.

    On a further note, how should hdparm -d behave on my controller, the
    relivant lines from dmesg are:

    SIS5513: IDE controller at PCI slot 00:01.1
    SIS5513: chipset revision 8
    SIS5513: not 100% native mode: will probe irqs later
    SIS5513: SiS551x ATA 16 controller
    ide0: BM-DMA at 0xf870-0xf877, BIOS settings: hda:pio, hdb:pio
    SIS5513: simplex device: DMA disabled
    ide1: SIS5513 Bus-Master DMA disabled (BIOS)
    hda: WDC AC21000H, ATA DISK drive
    hdc: Maxtor 6Y080L0, ATA DISK drive

    "hdparm -d 1 /dev/hdc" returns an operation not permitted, but "hdparm
    -d 1 /dev/hda" is successful and results in future calls to "hdparm -d
    1 /dev/hdc" seemingly locking the computer.

    > Are you sure that it doesn't happen on 2.6.1? Maybe you've used a bit
    > different config (ie. compiled without DMA support)?

    Oops, on further research it did exhibit the exact same problem.
    Sorry about the misdiagnosis.

    Let me know how I can continue to help.


    [Sorry about my tardy response]

    --- linux-2.4.24-orig/drivers/ide/ide-iops.c 2003-11-28 18:26:20.000000000 +0000
    +++ linux-2.4.24/drivers/ide/ide-iops.c 2004-01-27 05:19:41.000000000 +0000
    @@ -912,7 +912,8 @@
    // ide_delay_50ms();

    #if defined(CONFIG_BLK_DEV_IDEDMA) && !defined(CONFIG_DMA_NONPCI)
    - hwif->ide_dma_host_off(drive);
    + if (hwif->ide_dma_check) /* Check if host supports DMA */
    + hwif->ide_dma_host_off(drive);

    @@ -980,10 +981,13 @@
    drive->id->dma_1word &= ~0x0F00;

    #if defined(CONFIG_BLK_DEV_IDEDMA) && !defined(CONFIG_DMA_NONPCI)
    - if (speed >= XFER_SW_DMA_0)
    - hwif->ide_dma_host_on(drive);
    - else
    - hwif->ide_dma_off_quietly(drive);
    + if (speed >= XFER_SW_DMA_0) {
    + if (hwif->ide_dma_check) /* Check if host supports DMA */
    + hwif->ide_dma_host_on(drive);
    + } else {
    + if (hwif->ide_dma_check) /* Check if host supports DMA */
    + hwif->ide_dma_off_quietly(drive);
    + }

    switch(speed) {
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