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>

1 files changed, 12 insertions, 2 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 3784af395576..ba84d8a37545 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -211,7 +211,7 @@ enum {
 
         ATA_PFLAG_SUSPENDED     = (1 << 17), /* port is suspended (power) */
         ATA_PFLAG_PM_PENDING    = (1 << 18), /* PM operation pending */
-        ATA_PFLAG_GTM_VALID     = (1 << 19), /* acpi_gtm data valid */
+        ATA_PFLAG_INIT_GTM_VALID = (1 << 19), /* initial gtm data valid */
 
         /* struct ata_queued_cmd flags */
         ATA_QCFLAG_ACTIVE       = (1 << 0), /* cmd not yet ack'd to scsi lyer */
@@ -653,7 +653,7 @@ struct ata_port {
 
 #ifdef CONFIG_ATA_ACPI
         acpi_handle             acpi_handle;
-        struct ata_acpi_gtm     acpi_gtm;
+        struct ata_acpi_gtm     __acpi_init_gtm; /* use ata_acpi_init_gtm() */
 #endif
         u8                      sector_buf[ATA_SECT_SIZE]; /* owned by EH */
 };
@@ -939,10 +939,20 @@ enum {
 
 /* libata-acpi.c */
 #ifdef CONFIG_ATA_ACPI
+static inline const struct ata_acpi_gtm *ata_acpi_init_gtm(struct ata_port *ap)
+{
+        if (ap->pflags & ATA_PFLAG_INIT_GTM_VALID)
+                return &ap->__acpi_init_gtm;
+        return NULL;
+}
 extern int ata_acpi_cbl_80wire(struct ata_port *ap);
 int ata_acpi_stm(struct ata_port *ap, const struct ata_acpi_gtm *stm);
 int ata_acpi_gtm(struct ata_port *ap, struct ata_acpi_gtm *stm);
 #else
+static inline const struct ata_acpi_gtm *ata_acpi_init_gtm(struct ata_port *ap)
+{
+        return NULL;
+}
 static inline int ata_acpi_cbl_80wire(struct ata_port *ap) { return 0; }
 #endif