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    Subject2.6.18 suspend regression on Intel Macs
    Well, I'm not sure it qualifies as a regression, because AFAIK no
    official kernels can s2ram/resume Intel Macs correctly out of the box.

    There has already been some discussion about the SCI_EN ACPI control bit
    not being set when the Mactel boxes come out of suspend to ram.

    The symptom is:
    irq 9: nobody cared (try booting with the "irqpoll" option)
    Disabling IRQ #9
    when the system comes out of sleep, making ACPI non-functional.

    Two days after having released 2.6.17, Linus commited a fix for this
    issue in his tree (commit 5603509137940f4cbc577281cee62110d4097b1b):

    @@ -812,6 +812,9 @@ static int irqrouter_resume(struct sys_d


    + /* Make sure SCI is enabled again (Apple firmware bug?) */
    + acpi_set_register(ACPI_BITREG_SCI_ENABLE, 1, ACPI_MTX_DO_NOT_LOCK);

    I since then used lightly patched 2.6.17 kernels on my MacMini without a
    problem. With the release of 2.6.18, I decided to switch to a vanilla
    kernel but I realized that the above issue reappeared.

    I tracked it down to the ACPI merge that took place on July 1st. More
    precisely the commit 967440e3be1af06ad4dc7bb18d2e3c16130fe067 (ACPI:
    ACPICA 20060623) contains the following hunk:

    @@ -635,6 +663,25 @@ acpi_status acpi_hw_register_write(u8 us

    case ACPI_REGISTER_PM1_CONTROL: /* 16-bit access */

    + /*
    + * Perform a read first to preserve certain bits (per ACPI spec)
    + *
    + * Note: This includes SCI_EN, we never want to change this bit
    + */
    + status = acpi_hw_register_read(ACPI_MTX_DO_NOT_LOCK,
    + &read_value);
    + if (ACPI_FAILURE(status)) {
    + goto unlock_and_exit;
    + }
    + /* Insert the bits to be preserved */
    + read_value);
    + /* Now we can write the data */
    status =
    acpi_hw_low_level_write(16, value,

    which makes Linus' fix a no-op, because it disallows setting the SCI_EN


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