Re: [PATCH v2] dma: rcar-dmac: use list_add() on rcar_dmac_desc_put()

From: Vinod Koul
Date: Sun May 29 2016 - 23:36:30 EST

On Mon, May 30, 2016 at 12:41:48AM +0000, Kuninori Morimoto wrote:
> From: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
> For each descriptor, in addition to the memory used by the descriptors
> structure itself, the driver allocates a list of chunks as well as a
> buffer for hardware descriptors. Descriptors themselves are preallocated,
> and allocation of the chunks and buffer is performed the first time the
> descriptor is used. The memory isn't freed when the transfer is completed,
> as the chunks and buffer will be needed again when the descriptor is
> reused internally, so the driver keeps the memory around.
> If only a few descriptors are used concurrently, the current
> list_add_tail() implementation will result in all preallocated descriptors
> being used before going back to the first one, and will thus allocate
> chunks and a buffer for all preallocated descriptors. Using list_add()
> will put the complete descriptor at the head of the list of available
> descriptors, so the next transfer will be more likely to reuse a
> descriptor that already has associated memory instead of one that has
> never been used before.

Applied after fixing subsystem name