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>

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 53f5afd..bbfccdb 100644 (file)
--- 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;