tree 08c9171d024b6659b29a4f9f7d95318430b75b6a
parent 562f0c2d771ee7be6b37fe015f94a929f8056120
author Tejun Heo <htejun@gmail.com> 1197698702 +0900
committer Jeff Garzik <jeff@garzik.org> 1197941594 -0500

libata-acpi: implement and use ata_acpi_init_gtm()

_GTM fetches currently configured transfer mode while _STM configures
controller according to _GTM parameter and prepares transfer mode
configuration TFs for _GTF.  In many cases _GTM and _STM
implementations are quite brittle and can't cope with configuration
changed by libata.

libata does not depend on ATA ACPI to configure devices.  The only
reason libata performs _GTM and _STM are to make _GTF evaluation
succeed and libata also doesn't care about how _GTF TFs configure
transfer mode.  It overrides that configuration anyway, so from
libata's POV, it doesn't matter what value is feeded to _STM as long
as evaluation succeeds for _STM and following _GTF.

This patch adds dev->__acpi_init_gtm and store initial _GTM values on
host initialization before modified by reset and mode configuration.
If the field is valid, ata_acpi_init_gtm() returns pointer to the
saved _GTM structure; otherwise, NULL.

This saved value is used for _STM during resume and peek at
BIOS/firmware programmed initial timing for later use.  The accessor
is there to make building w/o ACPI easy as dev->__acpi_init doesn't
exist if ACPI is not enabled.

On driver detach, the initial BIOS configuration is restored by
executing _STM with the initial _GTM values such that the next driver
can also use the initial BIOS configured values.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>