03 May, 2013

2 commits

  • Currently the OF DMA code uses a spin lock to protect the of_dma_list from
    concurrent access and a per controller reference count to protect the controller
    from being freed while a request operation is in progress. If
    of_dma_controller_free() is called for a controller who's reference count is not
    zero it will return -EBUSY and not remove the controller. This is fine up until
    here, but leaves the question what the caller of of_dma_controller_free() is
    supposed to do if the controller couldn't be freed. The only viable solution
    for the caller is to spin on of_dma_controller_free() until it returns success.
    E.g.

    do {
    ret = of_dma_controller_free(dev->of_node)
    } while (ret != -EBUSY);

    This is rather ugly and unnecessary and none of the current users of
    of_dma_controller_free() check it's return value anyway. Instead protect the
    list by a mutex. The mutex will be held as long as a request operation is in
    progress. So if of_dma_controller_free() is called while a request operation is
    in progress it will be put to sleep and only wake up once the request operation
    has finished.

    This means that it is no longer possible to register or unregister OF DMA
    controllers from a context where it's not possible to sleep. But I doubt that
    we'll ever need this.

    Also rename of_dma_get_controller back to of_dma_find_controller.

    Signed-off-by: Lars-Peter Clausen
    Acked-by: Arnd Bergmann
    Signed-off-by: Vinod Koul

    Lars-Peter Clausen
     
  • of_dma_request_slave_channel() currently does not drop the reference to the
    dma_spec of_node if no DMA controller matching the of_node could be found. This
    patch fixes it by always calling of_node_put().

    Signed-off-by: Lars-Peter Clausen
    Acked-by: Arnd Bergmann
    Reviewed-by: Jon Hunter
    Signed-off-by: Vinod Koul

    Lars-Peter Clausen
     

15 Apr, 2013

3 commits


14 Feb, 2013

3 commits