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Lars-Peter Clausen authored
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 <lars@metafoo.de> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
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