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SubjectRe: 2.6.18 suspend regression on Intel Macs
Hi!

> 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.
> http://marc.theaimsgroup.com/?l=linux-acpi&m=114957637501557&w=2
> http://marc.theaimsgroup.com/?l=linux-kernel&m=115005083610700&w=2
> http://bugme.osdl.org/show_bug.cgi?id=6670
>
> 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):

If fix was in 2.6.18-gitX, yes, that probably counts as a regression.

> 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,
> + ACPI_REGISTER_PM1_CONTROL,
> + &read_value);
> + if (ACPI_FAILURE(status)) {
> + goto unlock_and_exit;
> + }
> +
> + /* Insert the bits to be preserved */
> +
> + ACPI_INSERT_BITS(value, ACPI_PM1_CONTROL_PRESERVED_BITS,
> + read_value);
> +
> + /* Now we can write the data */
> +
> status =
> acpi_hw_low_level_write(16, value,
> &acpi_gbl_FADT->xpm1a_cnt_blk);
>
>
> which makes Linus' fix a no-op, because it disallows setting the SCI_EN
> bit.

Okay, just submit a (tested) patch. (And add massive comments why it
is neccessary on mac mini).
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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