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>

2 files changed, 39 insertions, 37 deletions

diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index 9e5fc5d75b2e..b3aeca368774 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -94,6 +94,9 @@ static void ata_acpi_associate_ide_port(struct ata_port *ap)
 
                 dev->acpi_handle = acpi_get_child(ap->acpi_handle, i);
         }
+
+        if (ata_acpi_gtm(ap, &ap->__acpi_init_gtm) == 0)
+                ap->pflags |= ATA_PFLAG_INIT_GTM_VALID;
 }
 
 static void ata_acpi_handle_hotplug(struct ata_port *ap, struct kobject *kobj,
@@ -199,7 +202,18 @@ void ata_acpi_associate(struct ata_host *host)
  */
 void ata_acpi_dissociate(struct ata_host *host)
 {
-        /* nada */
+        int i;
+
+        /* Restore initial _GTM values so that driver which attaches
+         * afterward can use them too.
+         */
+        for (i = 0; i < host->n_ports; i++) {
+                struct ata_port *ap = host->ports[i];
+                const struct ata_acpi_gtm *gtm = ata_acpi_init_gtm(ap);
+
+                if (ap->acpi_handle && gtm)
+                        ata_acpi_stm(ap, gtm);
+        }
 }
 
 /**
@@ -409,22 +423,21 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
 
 int ata_acpi_cbl_80wire(struct ata_port *ap)
 {
-        struct ata_acpi_gtm gtm;
+        const struct ata_acpi_gtm *gtm = ata_acpi_init_gtm(ap);
         int valid = 0;
 
-        /* No _GTM data, no information */
-        if (ata_acpi_gtm(ap, &gtm) < 0)
+        if (!gtm)
                 return 0;
 
         /* Split timing, DMA enabled */
-        if ((gtm.flags & 0x11) == 0x11 && gtm.drive[0].dma < 55)
+        if ((gtm->flags & 0x11) == 0x11 && gtm->drive[0].dma < 55)
                 valid |= 1;
-        if ((gtm.flags & 0x14) == 0x14 && gtm.drive[1].dma < 55)
+        if ((gtm->flags & 0x14) == 0x14 && gtm->drive[1].dma < 55)
                 valid |= 2;
         /* Shared timing, DMA enabled */
-        if ((gtm.flags & 0x11) == 0x01 && gtm.drive[0].dma < 55)
+        if ((gtm->flags & 0x11) == 0x01 && gtm->drive[0].dma < 55)
                 valid |= 1;
-        if ((gtm.flags & 0x14) == 0x04 && gtm.drive[0].dma < 55)
+        if ((gtm->flags & 0x14) == 0x04 && gtm->drive[0].dma < 55)
                 valid |= 2;
 
         /* Drive check */
@@ -612,27 +625,8 @@ static int ata_acpi_push_id(struct ata_device *dev)
  */
 int ata_acpi_on_suspend(struct ata_port *ap)
 {
-        unsigned long flags;
-        int rc;
-
-        /* proceed iff per-port acpi_handle is valid */
-        if (!ap->acpi_handle)
-                return 0;
-        BUG_ON(ap->flags & ATA_FLAG_ACPI_SATA);
-
-        /* store timing parameters */
-        rc = ata_acpi_gtm(ap, &ap->acpi_gtm);
-
-        spin_lock_irqsave(ap->lock, flags);
-        if (rc == 0)
-                ap->pflags |= ATA_PFLAG_GTM_VALID;
-        else
-                ap->pflags &= ~ATA_PFLAG_GTM_VALID;
-        spin_unlock_irqrestore(ap->lock, flags);
-
-        if (rc == -ENOENT)
-                rc = 0;
-        return rc;
+        /* nada */
+        return 0;
 }
 
 /**
@@ -647,14 +641,12 @@ int ata_acpi_on_suspend(struct ata_port *ap)
  */
 void ata_acpi_on_resume(struct ata_port *ap)
 {
+        const struct ata_acpi_gtm *gtm = ata_acpi_init_gtm(ap);
         struct ata_device *dev;
 
-        if (ap->acpi_handle && (ap->pflags & ATA_PFLAG_GTM_VALID)) {
-                BUG_ON(ap->flags & ATA_FLAG_ACPI_SATA);
-
-                /* restore timing parameters */
-                ata_acpi_stm(ap, &ap->acpi_gtm);
-        }
+        /* restore timing parameters */
+        if (ap->acpi_handle && gtm)
+                ata_acpi_stm(ap, gtm);
 
         /* schedule _GTF */
         ata_link_for_each_dev(dev, &ap->link)
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