linux-kernel - [PATCH] dmaengine: dw: clear LLP_[SD]_EN bits in last descriptor of a chain

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Date:	Mon, 21 Dec 2015 19:10:37 +0000
From:	Mans Rullgard <mans@...sr.com>
To:	Viresh Kumar <vireshk@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] dmaengine: dw: clear LLP_[SD]_EN bits in last descriptor of a chain

The datasheet requires that the LLP_[SD]_EN bits be cleared whenever
LLP.LOC is zero, i.e. in the last descriptor of a multi-block chain.
Make the driver do this.

Signed-off-by: Mans Rullgard <mans@...sr.com>
---
 drivers/dma/dw/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 7067b6ddc1db..ca7cafc82f6b 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -751,6 +751,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 		prev->lli.ctllo |= DWC_CTLL_INT_EN;
 
 	prev->lli.llp = 0;
+	prev->lli.ctllo &= ~(DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN);
 	first->txd.flags = flags;
 	first->total_len = len;
 
@@ -912,6 +913,7 @@ slave_sg_fromdev_fill_desc:
 		prev->lli.ctllo |= DWC_CTLL_INT_EN;
 
 	prev->lli.llp = 0;
+	prev->lli.ctllo &= ~(DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN);
 	first->total_len = total_len;
 
 	return &first->txd;
-- 
2.6.3

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