[PATCH] ahci: preserve PORTS_IMPL over host resets

Instead of writing 0xf blindly, preserve the content of write-once
PORTS_IMPL register over host resets.

This patch is taken from Jeff Garzik's AHCI init update patch.

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

1 files changed, 20 insertions, 3 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index bc6599e4f474..f2277be70c0f 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -421,6 +421,11 @@ static struct pci_driver ahci_pci_driver = {
 };
 
 
+static inline int ahci_nr_ports(u32 cap)
+{
+        return (cap & 0x1f) + 1;
+}
+
 static inline unsigned long ahci_port_base_ul (unsigned long base, unsigned int port)
 {
         return base + 0x100 + (port * 0x80);
@@ -630,11 +635,12 @@ static int ahci_deinit_port(void __iomem *port_mmio, u32 cap, const char **emsg)
 
 static int ahci_reset_controller(void __iomem *mmio, struct pci_dev *pdev)
 {
-        u32 cap_save, tmp;
+        u32 cap_save, impl_save, tmp;
 
         cap_save = readl(mmio + HOST_CAP);
         cap_save &= ( (1<<28) | (1<<17) );
         cap_save |= (1 << 27);
+        impl_save = readl(mmio + HOST_PORTS_IMPL);
 
         /* global controller reset */
         tmp = readl(mmio + HOST_CTL);
@@ -655,10 +661,21 @@ static int ahci_reset_controller(void __iomem *mmio, struct pci_dev *pdev)
                 return -EIO;
         }
 
+        /* turn on AHCI mode */
         writel(HOST_AHCI_EN, mmio + HOST_CTL);
         (void) readl(mmio + HOST_CTL);  /* flush */
+
+        /* These write-once registers are normally cleared on reset.
+         * Restore BIOS values... which we HOPE were present before
+         * reset.
+         */
+        if (!impl_save) {
+                impl_save = (1 << ahci_nr_ports(cap_save)) - 1;
+                dev_printk(KERN_WARNING, &pdev->dev,
+                           "PORTS_IMPL is zero, forcing 0x%x\n", impl_save);
+        }
         writel(cap_save, mmio + HOST_CAP);
-        writel(0xf, mmio + HOST_PORTS_IMPL);
+        writel(impl_save, mmio + HOST_PORTS_IMPL);
         (void) readl(mmio + HOST_PORTS_IMPL);   /* flush */
 
         if (pdev->vendor == PCI_VENDOR_ID_INTEL) {
@@ -1467,7 +1484,7 @@ static int ahci_host_init(struct ata_probe_ent *probe_ent)
 
         hpriv->cap = readl(mmio + HOST_CAP);
         hpriv->port_map = readl(mmio + HOST_PORTS_IMPL);
-        probe_ent->n_ports = (hpriv->cap & 0x1f) + 1;
+        probe_ent->n_ports = ahci_nr_ports(hpriv->cap);
 
         VPRINTK("cap 0x%x  port_map 0x%x  n_ports %d\n",
                 hpriv->cap, hpriv->port_map, probe_ent->n_ports);