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    Subject[PATCH 4.14 020/165] usb: gadget: u_audio: update hw_ptr in iso_complete after data copied
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Joshua Frkuska <joshua_frkuska@mentor.com>

    [ Upstream commit 6b37bd78d30c890e575a1bda22978d1d2a233362 ]

    In u_audio_iso_complete, the runtime hw_ptr is updated before the
    data is actually copied over to/from the buffer/dma area. When
    ALSA uses this hw_ptr, the data may not actually be available to
    be used. This causes trash/stale audio to play/record. This
    patch updates the hw_ptr after the data has been copied to avoid
    this.

    Fixes: 132fcb460839 ("usb: gadget: Add Audio Class 2.0 Driver")
    Signed-off-by: Joshua Frkuska <joshua_frkuska@mentor.com>
    Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
    Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/usb/gadget/function/u_audio.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/drivers/usb/gadget/function/u_audio.c
    +++ b/drivers/usb/gadget/function/u_audio.c
    @@ -152,7 +152,6 @@ static void u_audio_iso_complete(struct
    update_alsa = true;

    hw_ptr = prm->hw_ptr;
    - prm->hw_ptr = (prm->hw_ptr + req->actual) % prm->dma_bytes;

    spin_unlock_irqrestore(&prm->lock, flags);

    @@ -177,6 +176,11 @@ static void u_audio_iso_complete(struct
    }
    }

    + spin_lock_irqsave(&prm->lock, flags);
    + /* update hw_ptr after data is copied to memory */
    + prm->hw_ptr = (hw_ptr + req->actual) % prm->dma_bytes;
    + spin_unlock_irqrestore(&prm->lock, flags);
    +
    exit:
    if (usb_ep_queue(ep, req, GFP_ATOMIC))
    dev_err(uac->card->dev, "%d Error!\n", __LINE__);

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