linux-kernel - [PATCH] dma: rcar-dmac: use list_add() on rcar_dmac_desc

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Date:	Fri, 22 Apr 2016 01:50:04 +0000
From:	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:	Vinod Koul <vinod.koul@...el.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
CC:	sakato <ryusuke.sakato.bx@...esas.com>,
	OSD2 ML <osd2@...renesas.com>, <dmaengine@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] dma: rcar-dmac: use list_add() on rcar_dmac_desc_put()


From: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>

Current rcar_dmac_desc_put() is using list_add_tail() in order to
push used descriptor to list of free descriptors, and next DMA transfer
try to reuse it from this list. But because it is using *_tail(),
this reuse effect can't be obtained without using all of them.
For a longer-term solution, we should allocate hardware descriptors
using GFP_KERNEL instead of GFP_NOWAIT, but it is difficult today.
This patch uses list_add() instead of list_add_tail() for short-term
solution.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
---
 drivers/dma/sh/rcar-dmac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 02b86c6..616c63a 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -519,7 +519,7 @@ static void rcar_dmac_desc_put(struct rcar_dmac_chan *chan,
 
 	spin_lock_irqsave(&chan->lock, flags);
 	list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free);
-	list_add_tail(&desc->node, &chan->desc.free);
+	list_add(&desc->node, &chan->desc.free);
 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 
-- 
1.9.1