• Andiry Xu's avatar
    xHCI: Implement AMD PLL quirk · c41136b0
    Andiry Xu authored
    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: default avatarAndiry Xu <andiry.xu@amd.com>
    Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
    c41136b0
xhci.c 84.3 KB