• William Wu's avatar
    usb: dwc2: alloc dma aligned buffer for isoc split in · af424a41
    William Wu authored
    The commit 3bc04e28 ("usb: dwc2: host: Get aligned DMA in
    a more supported way") rips out a lot of code to simply the
    allocation of aligned DMA. However, it also introduces a new
    issue when use isoc split in transfer.
    
    In my test case, I connect the dwc2 controller with an usb hs
    Hub (GL852G-12), and plug an usb fs audio device (Plantronics
    headset) into the downstream port of Hub. Then use the usb mic
    to record, we can find noise when playback.
    
    It's because that the usb Hub uses an MDATA for the first
    transaction and a DATA0 for the second transaction for the isoc
    split in transaction. An typical isoc split in transaction sequence
    like this:
    
    - SSPLIT IN transaction
    - CSPLIT IN transaction
      - MDATA packet
    - CSPLIT IN transaction
      - DATA0 packet
    
    The DMA address of MDATA (urb->dma) is always DWORD-aligned, but
    the DMA address of DATA0 (urb->dma + qtd->isoc_split_offset) may
    not be DWORD-aligned, it depends on the qtd->isoc_split_offset (the
    length of MDATA). In my test case, the length of MDATA is usually
    unaligned, this cause DATA0 packet transmission error.
    
    This patch use kmem_cache to allocate aligned DMA buf for isoc
    split in transaction. Note that according to usb 2.0 spec, the
    maximum data payload size is 1023 bytes for each fs isoc ep,
    and the maximum allowable interrupt data payload size is 64 bytes
    or less for fs interrupt ep. So we set the size of object to be
    1024 bytes in the kmem cache.
    Tested-by: default avatarGevorg Sahakyan <sahakyan@synopsys.com>
    Tested-by: default avatarHeiko Stuebner <heiko@sntech.de>
    Acked-by: Minas Harutyunyan hminas@synopsys.com>
    Signed-off-by: default avatarWilliam Wu <william.wu@rock-chips.com>
    Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
    Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
    af424a41
hcd.h 28.3 KB