linux-kernel - [PATCH] dmaengine: rcar-dmac: read DMATCRB instead of DMATCR for residue

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Date:   Mon, 16 Oct 2017 05:28:47 +0000
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vinod.koul@...el.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     "Niklas Söderlund" 
        <niklas.soderlund+renesas@...natech.se>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@...esas.com>
Subject: [PATCH] dmaengine: rcar-dmac: read DMATCRB instead of DMATCR for residue

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

SYS/RT/Audio DMAC have both TCR/TCRB register.
Its difference is transfer counter value of read (= TCR)
or write (= TCRB). The relationship is like below.

         TCR       TCRB
 [SOURCE] -> [DMAC] -> [DESTINATION]

Thus, we want to read TCRB instead of TCR for residue.
Otherwise, Sound Capture has noise after PluseAudio support
(= 07b7acb51d2 ("ASoC: rsnd: update pointer more accurate"))

Signed-off-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@...esas.com>
[Kuninori: added detail information in log]
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 2b2c7db..50c4950 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1310,7 +1310,7 @@ static unsigned int rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
 	}
 
 	/* Add the residue for the current chunk. */
-	residue += rcar_dmac_chan_read(chan, RCAR_DMATCR) << desc->xfer_shift;
+	residue += rcar_dmac_chan_read(chan, RCAR_DMATCRB) << desc->xfer_shift;
 
 	return residue;
 }
-- 
1.9.1