linux-kernel - [PATCH] dmaengine: pl330: Handle xferred count if DMAMOV hasn't finished

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Message-Id: <1478043867-22597-1-git-send-email-smbarber@chromium.org>
Date:   Tue,  1 Nov 2016 16:44:27 -0700
From:   Stephen Barber <smbarber@...omium.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Dan Williams <dan.j.williams@...el.com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dylan Reid <dgreid@...omium.org>,
        Hsin-Yu Chao <hychao@...omium.org>,
        Stephen Barber <smbarber@...omium.org>
Subject: [PATCH] dmaengine: pl330: Handle xferred count if DMAMOV hasn't finished

After executing DMAGO it's possible that a request can come in for the
current xferred count, but if that happens too soon then DMAMOV SAR/DAR
may not have yet completed. If that happens, we should explicitly return 0
since nothing has been transferred yet.

Signed-off-by: Stephen Barber <smbarber@...omium.org>
---
 drivers/dma/pl330.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 030fe05..458a712 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2263,6 +2263,11 @@ static int pl330_get_current_xferred_count(struct dma_pl330_chan *pch,
 	}
 	pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
 	pm_runtime_put_autosuspend(pl330->ddma.dev);
+
+	/* If DMAMOV hasn't finished yet, SAR/DAR can be zero */
+	if (!val)
+		return 0;
+
 	return val - addr;
 }
 
-- 
2.8.0.rc3.226.g39d4020