ahci: implement skip_host_reset parameter

Under certain circumstances (SSP turned off by the BIOS) and for
debugging purposes, skipping global controller reset is helpful.  Add
a kernel parameter for it.

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

1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 53f5afd9420c..bbfccdbba3ab 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -49,6 +49,10 @@
 #define DRV_NAME        "ahci"
 #define DRV_VERSION     "3.0"
 
+static int ahci_skip_host_reset;
+module_param_named(skip_host_reset, ahci_skip_host_reset, int, 0444);
+MODULE_PARM_DESC(skip_host_reset, "skip global host reset (0=don't skip, 1=skip)");
+
 static int ahci_enable_alpm(struct ata_port *ap,
                 enum link_pm policy);
 static void ahci_disable_alpm(struct ata_port *ap);
@@ -1088,29 +1092,35 @@ static int ahci_reset_controller(struct ata_host *host)
         ahci_enable_ahci(mmio);
 
         /* global controller reset */
-        tmp = readl(mmio + HOST_CTL);
-        if ((tmp & HOST_RESET) == 0) {
-                writel(tmp | HOST_RESET, mmio + HOST_CTL);
-                readl(mmio + HOST_CTL); /* flush */
-        }
+        if (!ahci_skip_host_reset) {
+                tmp = readl(mmio + HOST_CTL);
+                if ((tmp & HOST_RESET) == 0) {
+                        writel(tmp | HOST_RESET, mmio + HOST_CTL);
+                        readl(mmio + HOST_CTL); /* flush */
+                }
 
-        /* reset must complete within 1 second, or
-         * the hardware should be considered fried.
-         */
-        ssleep(1);
+                /* reset must complete within 1 second, or
+                 * the hardware should be considered fried.
+                 */
+                ssleep(1);
 
-        tmp = readl(mmio + HOST_CTL);
-        if (tmp & HOST_RESET) {
-                dev_printk(KERN_ERR, host->dev,
-                           "controller reset failed (0x%x)\n", tmp);
-                return -EIO;
-        }
+                tmp = readl(mmio + HOST_CTL);
+                if (tmp & HOST_RESET) {
+                        dev_printk(KERN_ERR, host->dev,
+                                   "controller reset failed (0x%x)\n", tmp);
+                        return -EIO;
+                }
 
-        /* turn on AHCI mode */
-        ahci_enable_ahci(mmio);
+                /* turn on AHCI mode */
+                ahci_enable_ahci(mmio);
 
-        /* some registers might be cleared on reset.  restore initial values */
-        ahci_restore_initial_config(host);
+                /* Some registers might be cleared on reset.  Restore
+                 * initial values.
+                 */
+                ahci_restore_initial_config(host);
+        } else
+                dev_printk(KERN_INFO, host->dev,
+                           "skipping global host reset\n");
 
         if (pdev->vendor == PCI_VENDOR_ID_INTEL) {
                 u16 tmp16;