linux-kernel - [PATCH] dmaengine/dw_dmac fix: dwc_scan_descriptors must compare first desc address also with llp

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Date:	Thu, 24 Mar 2011 11:32:15 +0530
From:	Viresh Kumar <viresh.kumar@...com>
To:	<vinod.koul@...el.com>, <dan.j.williams@...el.com>,
	<linux-kernel@...r.kernel.org>, <jamie@...ieiles.com>
Cc:	<shiraz.hashim@...com>, <armando.visconti@...com>,
	<ajay.khandelwal@...com>, <amit.goel@...com>,
	<viresh.linux@...il.com>, Viresh Kumar <viresh.kumar@...com>
Subject: [PATCH] dmaengine/dw_dmac fix: dwc_scan_descriptors must compare first desc address also with llp

dwc_scan_descriptors scans all descriptors from active_list in case transfer is
not completed.  It compares first_desc->lli.llp, and then all childrens of its
tx_list. But it doesn't compare its own address, i.e. first_desc->txd.phys, as
this is what we have initially programmed into the controller register. So this
causes dma to stop and finish a transfer, which was never started. And thus
fail.

Signed-off-by: Viresh Kumar <viresh.kumar@...com>
---
 drivers/dma/dw_dmac.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index b95e6d3..1bd4803 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -304,6 +304,11 @@ static void dwc_scan_descriptors(struct dw_dma *dw, struct dw_dma_chan *dwc)
 	dev_vdbg(chan2dev(&dwc->chan), "scan_descriptors: llp=0x%x\n", llp);
 
 	list_for_each_entry_safe(desc, _desc, &dwc->active_list, desc_node) {
+		/* check first descriptors addr */
+		if (desc->txd.phys == llp)
+			return;
+
+		/* check first descriptors llp */
 		if (desc->lli.llp == llp)
 			/* This one is currently in progress */
 			return;
-- 
1.7.2.2

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