xHCI: Implement AMD PLL quirk

This patch disable the optional PM feature inside the Hudson3 platform under
the following conditions:

1. If an isochronous device is connected to xHCI port and is active;
2. Optional PM feature that powers down the internal Bus PLL when the link is
   in low power state is enabled.

The PM feature needs to be disabled to eliminate PLL startup delays when the
link comes out of low power state. The performance of DMA data transfer could
be impacted if system delay were encountered and in addition to the PLL start
up delays. Disabling the PM would leave room for unpredictable system delays
in order to guarantee uninterrupted data transfer to isochronous audio or
video stream devices that require time sensitive information. If data in an
audio/video stream was interrupted then erratic audio or video performance
may be encountered.

AMD PLL quirk is already implemented in OHCI/EHCI driver. After moving the
quirk code to pci-quirks.c and export them, xHCI driver can call it directly
without having the quirk implementation in itself.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index c41358e4b8cc..81b976e45880 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -550,6 +550,9 @@ void xhci_stop(struct usb_hcd *hcd)
         del_timer_sync(&xhci->event_ring_timer);
 #endif
 
+        if (xhci->quirks & XHCI_AMD_PLL_FIX)
+                usb_amd_dev_put();
+
         xhci_dbg(xhci, "// Disabling event ring interrupts\n");
         temp = xhci_readl(xhci, &xhci->op_regs->status);
         xhci_writel(xhci, temp & ~STS_EINT, &xhci->op_regs->status);