libata-acpi: implement dev->gtf_cache and evaluate _GTF right after _STM during resume

On certain implementations, _GTF evaluation depends on preceding _STM
and both can be pretty picky about the configuration.  Using _GTM
result cached during controller initialization satisfies the most
neurotic _STM implementation.  However, libata evaluates _GTF after
reset during device configuration and the hardware state can be
different from what _GTF expects and can cause evaluation failure.

This patch adds dev->gtf_cache and updates ata_dev_get_GTF() such that
it uses the cached value if available.  Cache is cleared with a call
to ata_acpi_clear_gtf().

Because for SATA ACPI nodes _GTF must be evaluated after _SDD which
can't be done till IDENTIFY is complete, _GTF caching from
ata_acpi_on_resume() is used only for IDE ACPI nodes.

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

2 files changed, 50 insertions, 20 deletions

diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index b3aeca3687..e0dd132fd4 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -41,6 +41,12 @@ static int is_pci_dev(struct device *dev)
         return (dev->bus == &pci_bus_type);
 }
 
+static void ata_acpi_clear_gtf(struct ata_device *dev)
+{
+        kfree(dev->gtf_cache);
+        dev->gtf_cache = NULL;
+}
+
 /**
  * ata_acpi_associate_sata_port - associate SATA port with ACPI objects
  * @ap: target SATA port
@@ -327,7 +333,6 @@ EXPORT_SYMBOL_GPL(ata_acpi_stm);
  * ata_dev_get_GTF - get the drive bootup default taskfile settings
  * @dev: target ATA device
  * @gtf: output parameter for buffer containing _GTF taskfile arrays
- * @ptr_to_free: pointer which should be freed
  *
  * This applies to both PATA and SATA drives.
  *
@@ -344,8 +349,7 @@ EXPORT_SYMBOL_GPL(ata_acpi_stm);
  * Number of taskfiles on success, 0 if _GTF doesn't exist or doesn't
  * contain valid data.
  */
-static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
-                           void **ptr_to_free)
+static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf)
 {
         struct ata_port *ap = dev->link->ap;
         acpi_status status;
@@ -353,6 +357,12 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
         union acpi_object *out_obj;
         int rc = 0;
 
+        /* if _GTF is cached, use the cached value */
+        if (dev->gtf_cache) {
+                out_obj = dev->gtf_cache;
+                goto done;
+        }
+
         /* set up output buffer */
         output.length = ACPI_ALLOCATE_BUFFER;
         output.pointer = NULL;  /* ACPI-CA sets this; save/free it later */
@@ -363,6 +373,7 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
 
         /* _GTF has no input parameters */
         status = acpi_evaluate_object(dev->acpi_handle, "_GTF", NULL, &output);
+        out_obj = dev->gtf_cache = output.pointer;
 
         if (ACPI_FAILURE(status)) {
                 if (status != AE_NOT_FOUND) {
@@ -383,7 +394,6 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
                 goto out_free;
         }
 
-        out_obj = output.pointer;
         if (out_obj->type != ACPI_TYPE_BUFFER) {
                 ata_dev_printk(dev, KERN_WARNING,
                                "_GTF unexpected object type 0x%x\n",
@@ -398,18 +408,19 @@ static int ata_dev_get_GTF(struct ata_device *dev, struct ata_acpi_gtf **gtf,
                 goto out_free;
         }
 
-        *ptr_to_free = out_obj;
-        *gtf = (void *)out_obj->buffer.pointer;
+ done:
         rc = out_obj->buffer.length / REGS_PER_GTF;
-
-        if (ata_msg_probe(ap))
-                ata_dev_printk(dev, KERN_DEBUG, "%s: returning "
-                        "gtf=%p, gtf_count=%d, ptr_to_free=%p\n",
-                        __FUNCTION__, *gtf, rc, *ptr_to_free);
+        if (gtf) {
+                *gtf = (void *)out_obj->buffer.pointer;
+                if (ata_msg_probe(ap))
+                        ata_dev_printk(dev, KERN_DEBUG,
+                                       "%s: returning gtf=%p, gtf_count=%d\n",
+                                       __FUNCTION__, *gtf, rc);
+        }
         return rc;
 
  out_free:
-        kfree(output.pointer);
+        ata_acpi_clear_gtf(dev);
         return rc;
 }
 
@@ -533,11 +544,10 @@ static int taskfile_load_raw(struct ata_device *dev,
 static int ata_acpi_exec_tfs(struct ata_device *dev)
 {
         struct ata_acpi_gtf *gtf = NULL;
-        void *ptr_to_free = NULL;
         int gtf_count, i, rc;
 
         /* get taskfiles */
-        gtf_count = ata_dev_get_GTF(dev, &gtf, &ptr_to_free);
+        gtf_count = ata_dev_get_GTF(dev, &gtf);
 
         /* execute them */
         for (i = 0, rc = 0; i < gtf_count; i++) {
@@ -551,7 +561,7 @@ static int ata_acpi_exec_tfs(struct ata_device *dev)
                         rc = tmp;
         }
 
-        kfree(ptr_to_free);
+        ata_acpi_clear_gtf(dev);
 
         if (rc == 0)
                 return gtf_count;
@@ -644,13 +654,31 @@ void ata_acpi_on_resume(struct ata_port *ap)
         const struct ata_acpi_gtm *gtm = ata_acpi_init_gtm(ap);
         struct ata_device *dev;
 
-        /* restore timing parameters */
-        if (ap->acpi_handle && gtm)
+        if (ap->acpi_handle && gtm) {
+                /* _GTM valid */
+
+                /* restore timing parameters */
                 ata_acpi_stm(ap, gtm);
 
-        /* schedule _GTF */
-        ata_link_for_each_dev(dev, &ap->link)
-                dev->flags |= ATA_DFLAG_ACPI_PENDING;
+                /* _GTF should immediately follow _STM so that it can
+                 * use values set by _STM.  Cache _GTF result and
+                 * schedule _GTF.
+                 */
+                ata_link_for_each_dev(dev, &ap->link) {
+                        ata_acpi_clear_gtf(dev);
+                        if (ata_dev_get_GTF(dev, NULL) >= 0)
+                                dev->flags |= ATA_DFLAG_ACPI_PENDING;
+                }
+        } else {
+                /* SATA _GTF needs to be evaulated after _SDD and
+                 * there's no reason to evaluate IDE _GTF early
+                 * without _STM.  Clear cache and schedule _GTF.
+                 */
+                ata_link_for_each_dev(dev, &ap->link) {
+                        ata_acpi_clear_gtf(dev);
+                        dev->flags |= ATA_DFLAG_ACPI_PENDING;
+                }
+        }
 }
 
 /**
@@ -735,4 +763,5 @@ int ata_acpi_on_devcfg(struct ata_device *dev)
  */
 void ata_acpi_on_disable(struct ata_device *dev)
 {
+        ata_acpi_clear_gtf(dev);
 }
diff --git a/include/linux/libata.h b/include/linux/libata.h
index ba84d8a375..cb91280be9 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -498,6 +498,7 @@ struct ata_device {
         struct scsi_device      *sdev;          /* attached SCSI device */
 #ifdef CONFIG_ATA_ACPI
         acpi_handle             acpi_handle;
+        union acpi_object       *gtf_cache;
 #endif
         /* n_sector is used as CLEAR_OFFSET, read comment above CLEAR_OFFSET */
         u64                     n_sectors;      /* size of device, if ATA */