libata: Check PCI sub-class code before disabling AHCI

This patch adds functionality to check the PCI sub-class code of an
AHCI capable device before disabling AHCI.  It fixes a bug where an
ICH7 sata controller is being setup by the BIOS as sub-class 1 (ide)
and the AHCI control registers weren't being initialized, thus causing
an IO error in piix_disable_ahci().

Signed-off-by: Gregory Felix <greg.felix@gmail.com>

1 files changed, 13 insertions, 6 deletions

diff --git a/drivers/scsi/ata_piix.c b/drivers/scsi/ata_piix.c
index 3be546439252..a2cfade2c1c6 100644
--- a/drivers/scsi/ata_piix.c
+++ b/drivers/scsi/ata_piix.c
@@ -38,6 +38,7 @@ enum {
         PIIX_IOCFG              = 0x54, /* IDE I/O configuration register */
         ICH5_PMR                = 0x90, /* port mapping register */
         ICH5_PCS                = 0x92, /* port control and status */
+        PIIX_SCC                = 0x0A, /* sub-class code register */
 
         PIIX_FLAG_AHCI          = (1 << 28), /* AHCI possible */
         PIIX_FLAG_CHECKINTR     = (1 << 29), /* make sure PCI INTx enabled */
@@ -62,6 +63,8 @@ enum {
         ich6_sata_rm            = 4,
         ich7_sata               = 5,
         esb2_sata               = 6,
+
+        PIIX_AHCI_DEVICE        = 6,
 };
 
 static int piix_init_one (struct pci_dev *pdev,
@@ -574,11 +577,11 @@ static int piix_disable_ahci(struct pci_dev *pdev)
         addr = pci_resource_start(pdev, AHCI_PCI_BAR);
         if (!addr || !pci_resource_len(pdev, AHCI_PCI_BAR))
                 return 0;
-        
+
         mmio = ioremap(addr, 64);
         if (!mmio)
                 return -ENOMEM;
-        
+
         tmp = readl(mmio + AHCI_GLOBAL_CTL);
         if (tmp & AHCI_ENABLE) {
                 tmp &= ~AHCI_ENABLE;
@@ -588,7 +591,7 @@ static int piix_disable_ahci(struct pci_dev *pdev)
                 if (tmp & AHCI_ENABLE)
                         rc = -EIO;
         }
-        
+
         iounmap(mmio);
         return rc;
 }
@@ -626,9 +629,13 @@ static int piix_init_one (struct pci_dev *pdev, const struct pci_device_id *ent)
         port_info[1] = NULL;
 
         if (port_info[0]->host_flags & PIIX_FLAG_AHCI) {
-                int rc = piix_disable_ahci(pdev);
-                if (rc)
-                        return rc;
+               u8 tmp;
+               pci_read_config_byte(pdev, PIIX_SCC, &tmp);
+               if (tmp == PIIX_AHCI_DEVICE) {
+                       int rc = piix_disable_ahci(pdev);
+                       if (rc)
+                           return rc;
+               }
         }
 
         if (port_info[0]->host_flags & PIIX_FLAG_COMBINED) {